diff --git a/_locales/en/messages.json b/_locales/en/messages.json
index c8e943234..5f091a5ea 100644
--- a/_locales/en/messages.json
+++ b/_locales/en/messages.json
@@ -3246,6 +3246,114 @@
     "description": "Button to dismiss pop-up dialog when user-initiated task has gone wrong"
   },
 
+  "unknown-sgnl-link": {
+    "message": "Sorry, that sgnl:// link didn't make sense!",
+    "description": "Shown if you click on a sgnl:// link not currently supported by Desktop"
+  },
+
+  "GroupV2--join--invalid-link--title": {
+    "message": "Invalid Link",
+    "description": "Shown if we are unable to parse a group link"
+  },
+  "GroupV2--join--invalid-link": {
+    "message": "This is not a valid group link. Make sure the entire link is intact and correct before attempting to join.",
+    "description": "Shown if we are unable to parse a group link"
+  },
+  "GroupV2--join--prompt": {
+    "message": "Do you want to join this group and share your name and photo with its members?",
+    "description": "Shown when you click on a group link to confirm"
+  },
+  "GroupV2--join--already-in-group": {
+    "message": "You're already in this group.",
+    "description": "Shown if you click a group link for a group where you're already a member"
+  },
+  "GroupV2--join--already-awaiting-approval": {
+    "message": "You have already requested approval to join this group.",
+    "description": "Shown if you click a group link for a group where you've already requested approval'"
+  },
+
+  "GroupV2--join--unknown-link-version--title": {
+    "message": "Unknown link version",
+    "description": "This group link is no longer valid."
+  },
+  "GroupV2--join--unknown-link-version": {
+    "message": "This link is not supported by this version of Signal Desktop.",
+    "description": "Shown if you click a group link and we can't get information about it"
+  },
+  "GroupV2--join--link-revoked--title": {
+    "message": "Can’t Join Group",
+    "description": "Shown if you click a group link and we can't get information about it"
+  },
+  "GroupV2--join--link-revoked": {
+    "message": "This group link is no longer valid.",
+    "description": "Shown if you click a group link and we can't get information about it"
+  },
+  "GroupV2--join--prompt-with-approval": {
+    "message": "An admin of this group must approve your request before you can join this group. If approved, your name and photo will be shared with its members.",
+    "description": "Shown when you click on a group link to confirm, if it requires admin approval"
+  },
+  "GroupV2--join--join-button": {
+    "message": "Join",
+    "description": "The button to join the group"
+  },
+  "GroupV2--join--request-to-join-button": {
+    "message": "Request to Join",
+    "description": "The button to join the group, if approval is required"
+  },
+  "GroupV2--join--cancel-request-to-join": {
+    "message": "Cancel Request",
+    "description": "The button to cancel request to join the group"
+  },
+  "GroupV2--join--cancel-request-to-join--confirmation": {
+    "message": "Cancel your request to join this group?",
+    "description": "A confirmation message that shows after you click the button"
+  },
+  "GroupV2--join--cancel-request-to-join--yes": {
+    "message": "Yes",
+    "description": "Choosing to continue in the cancel join confirmation dialog"
+  },
+  "GroupV2--join--cancel-request-to-join--no": {
+    "message": "No",
+    "description": "Choosing not to continue in the cancel join confirmation dialog"
+  },
+  "GroupV2--join--member-count--single": {
+    "message": "1 member",
+    "description": "Shown in the metadata section if group has just one member"
+  },
+  "GroupV2--join--member-count--multiple": {
+    "message": "$count$ members",
+    "description": "Shown in the metadata section if group has more than one member",
+    "placeholders": {
+      "count": {
+        "content": "$1",
+        "example": "12"
+      }
+    }
+  },
+  "GroupV2--join--group-metadata": {
+    "message": "Group · $memberCount$",
+    "description": "A holder for two pieces of information - the type of conversation, and the member count",
+    "placeholders": {
+      "memberCount": {
+        "content": "$1",
+        "example": "12 members"
+      }
+    }
+  },
+  "GroupV2--join--requested": {
+    "message": "Your request to join has been sent to the group admin. You’ll be notified when they take action.",
+    "description": "Shown in composition area when you've requested to join a group"
+  },
+
+  "GroupV2--join--general-join-failure--title": {
+    "message": "Link Error",
+    "description": "Shown if something went wrong when you try to join via a group link"
+  },
+  "GroupV2--join--general-join-failure": {
+    "message": "Joining via this link failed. Try joining again later.",
+    "description": "Shown if something went wrong when you try to join via a group link"
+  },
+
   "GroupV2--admin": {
     "message": "Admin",
     "description": "Label for a group administrator"
diff --git a/js/modules/signal.js b/js/modules/signal.js
index 7353e7f7a..1daad5214 100644
--- a/js/modules/signal.js
+++ b/js/modules/signal.js
@@ -79,6 +79,9 @@ const {
 const {
   createGroupV1MigrationModal,
 } = require('../../ts/state/roots/createGroupV1MigrationModal');
+const {
+  createGroupV2JoinModal,
+} = require('../../ts/state/roots/createGroupV2JoinModal');
 const { createLeftPane } = require('../../ts/state/roots/createLeftPane');
 const {
   createGroupV2Permissions,
@@ -340,6 +343,7 @@ exports.setup = (options = {}) => {
     createConversationHeader,
     createGroupLinkManagement,
     createGroupV1MigrationModal,
+    createGroupV2JoinModal,
     createGroupV2Permissions,
     createLeftPane,
     createPendingInvites,
diff --git a/main.js b/main.js
index 4b2f66582..a14f1bb6f 100644
--- a/main.js
+++ b/main.js
@@ -1428,7 +1428,7 @@ function getIncomingHref(argv) {
 }
 
 function handleSgnlHref(incomingHref) {
-  const { command, args } = parseSgnlHref(incomingHref, logger);
+  const { command, args, hash } = parseSgnlHref(incomingHref, logger);
   if (command === 'addstickers' && mainWindow && mainWindow.webContents) {
     console.log('Opening sticker pack from sgnl protocol link');
     const packId = args.get('pack_id');
@@ -1437,6 +1437,17 @@ function handleSgnlHref(incomingHref) {
       ? Buffer.from(packKeyHex, 'hex').toString('base64')
       : '';
     mainWindow.webContents.send('show-sticker-pack', { packId, packKey });
+  } else if (
+    command === 'signal.group' &&
+    hash &&
+    mainWindow &&
+    mainWindow.webContents
+  ) {
+    console.log('Showing group from sgnl protocol link');
+    mainWindow.webContents.send('show-group-via-link', { hash });
+  } else if (mainWindow && mainWindow.webContents) {
+    console.log('Showing warning that we cannot process link');
+    mainWindow.webContents.send('unknown-sgnl-link');
   } else {
     console.error('Unhandled sgnl link');
   }
diff --git a/preload.js b/preload.js
index 56549355b..bbc45422b 100644
--- a/preload.js
+++ b/preload.js
@@ -327,6 +327,21 @@ try {
     }
   });
 
+  ipc.on('show-group-via-link', (_event, info) => {
+    const { hash } = info;
+    const { showGroupViaLink } = window.Events;
+    if (showGroupViaLink) {
+      showGroupViaLink(hash);
+    }
+  });
+
+  ipc.on('unknown-sgnl-link', () => {
+    const { unknownSignalLink } = window.Events;
+    if (unknownSignalLink) {
+      unknownSignalLink();
+    }
+  });
+
   ipc.on('install-sticker-pack', (_event, info) => {
     const { packId, packKey } = info;
     const { installStickerPack } = window.Events;
diff --git a/protos/Groups.proto b/protos/Groups.proto
index 3a42b6b3d..7823ec8b1 100644
--- a/protos/Groups.proto
+++ b/protos/Groups.proto
@@ -206,3 +206,13 @@ message GroupInviteLink {
     GroupInviteLinkContentsV1 v1Contents = 1;
   }
 }
+
+message GroupJoinInfo {
+  bytes publicKey = 1;
+  bytes title = 2;
+  string avatar = 3;
+  uint32 memberCount = 4;
+  AccessControl.AccessRequired addFromInviteLink = 5;
+  uint32 version = 6;
+  bool pendingAdminApproval = 7;
+}
diff --git a/stylesheets/_modules.scss b/stylesheets/_modules.scss
index 20f18711d..ec517224e 100644
--- a/stylesheets/_modules.scss
+++ b/stylesheets/_modules.scss
@@ -4762,6 +4762,10 @@ button.module-conversation-details__action-button {
   }
 }
 
+.module-avatar__spinner-container {
+  padding: 4px;
+}
+
 .module-avatar--signal-blue {
   background-color: $ultramarine-ui-light;
 }
@@ -5846,6 +5850,9 @@ button.module-image__border-overlay:focus {
   }
 }
 
+.module-spinner__circle--on-avatar {
+  background-color: $color-white-alpha-40;
+}
 .module-spinner__circle--on-background {
   @include light-theme {
     background-color: $color-gray-05;
@@ -5874,6 +5881,9 @@ button.module-image__border-overlay:focus {
 .module-spinner__arc--on-progress-dialog {
   background-color: $ultramarine-ui-light;
 }
+.module-spinner__arc--on-avatar {
+  background-color: $color-white;
+}
 
 // Module: Highlighted Message Body
 
@@ -10576,6 +10586,60 @@ button.module-image__border-overlay:focus {
   @include button-primary;
 }
 
+// Module: GroupV2 Pending Approval Actions
+
+.module-group-v2-pending-approval-actions {
+  padding: 8px 16px 12px 16px;
+  max-width: 650px;
+  margin-left: auto;
+  margin-right: auto;
+
+  @include light-theme {
+    background: $color-white;
+  }
+
+  @include dark-theme {
+    background: $color-gray-95;
+  }
+}
+
+.module-group-v2-pending-approval-actions__message {
+  @include font-body-2;
+  text-align: center;
+  margin-bottom: 12px;
+
+  @include light-theme {
+    color: $color-gray-60;
+  }
+
+  @include dark-theme {
+    color: $color-gray-25;
+  }
+}
+
+.module-group-v2-pending-approval-actions__buttons {
+  display: flex;
+  flex-direction: row;
+  justify-content: center;
+}
+.module-group-v2-pending-approval-actions__buttons__button {
+  @include button-reset;
+  @include font-body-1-bold;
+
+  border-radius: 4px;
+
+  padding: 8px;
+  padding-left: 30px;
+  padding-right: 30px;
+
+  @include button-secondary;
+
+  @include light-theme {
+    color: $color-gray-60;
+    background-color: $color-gray-05;
+  }
+}
+
 // Module: Modal Host
 
 .module-modal-host__overlay {
@@ -10735,6 +10799,99 @@ button.module-image__border-overlay:focus {
   @include button-secondary;
 }
 
+// Module: GroupV2 Join Dialog
+
+.module-group-v2-join-dialog {
+  @include font-body-1;
+  border-radius: 8px;
+  width: 360px;
+  margin-left: auto;
+  margin-right: auto;
+  padding: 20px;
+
+  position: relative;
+
+  @include light-theme {
+    background-color: $color-white;
+  }
+  @include dark-theme {
+    background-color: $color-gray-95;
+  }
+}
+.module-group-v2-join-dialog__close-button {
+  @include button-reset;
+
+  position: absolute;
+  right: 12px;
+  top: 12px;
+
+  height: 24px;
+  width: 24px;
+
+  @include light-theme {
+    @include color-svg('../images/icons/v2/x-24.svg', $color-gray-75);
+  }
+
+  @include dark-theme {
+    @include color-svg('../images/icons/v2/x-24.svg', $color-gray-15);
+  }
+
+  &:focus {
+    @include keyboard-mode {
+      background-color: $ultramarine-ui-light;
+    }
+    @include dark-keyboard-mode {
+      background-color: $ultramarine-ui-dark;
+    }
+  }
+}
+.module-group-v2-join-dialog__title {
+  @include font-title-2;
+  text-align: center;
+  margin-top: 12px;
+  margin-bottom: 2px;
+}
+.module-group-v2-join-dialog__avatar {
+  text-align: center;
+}
+.module-group-v2-join-dialog__metadata {
+  text-align: center;
+}
+.module-group-v2-join-dialog__prompt {
+  margin-top: 40px;
+}
+.module-group-v2-join-dialog__buttons {
+  margin-top: 16px;
+
+  text-align: center;
+
+  display: flex;
+}
+.module-group-v2-join-dialog__button {
+  @include button-reset;
+  @include font-body-1-bold;
+
+  // Start flex basis at zero so text width doesn't affect layout. We want the buttons
+  //   evenly distributed.
+  flex: 1 1 0px;
+
+  border-radius: 4px;
+
+  padding: 8px;
+  padding-left: 15px;
+  padding-right: 15px;
+
+  @include button-primary;
+
+  &:not(:first-of-type) {
+    margin-left: 16px;
+  }
+}
+
+.module-group-v2-join-dialog__button--secondary {
+  @include button-secondary;
+}
+
 // Module: Progress Dialog
 
 .module-progress-dialog {
diff --git a/ts/ConversationController.ts b/ts/ConversationController.ts
index 8f99e8da1..57cb84728 100644
--- a/ts/ConversationController.ts
+++ b/ts/ConversationController.ts
@@ -2,6 +2,8 @@
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import { debounce, reduce, uniq, without } from 'lodash';
+import PQueue from 'p-queue';
+
 import dataInterface from './sql/Client';
 import {
   ConversationModelCollectionType,
@@ -150,6 +152,11 @@ export class ConversationController {
     return this._conversations.add(attributes);
   }
 
+  dangerouslyRemoveById(id: string): void {
+    this._conversations.remove(id);
+    this._conversations.resetLookups();
+  }
+
   getOrCreate(
     identifier: string | null,
     type: ConversationAttributesTypeType,
@@ -283,6 +290,16 @@ export class ConversationController {
     return this.ensureContactIds({ e164, uuid, highTrust: true });
   }
 
+  getOurConversationIdOrThrow(): string {
+    const conversationId = this.getOurConversationId();
+    if (!conversationId) {
+      throw new Error(
+        'getOurConversationIdOrThrow: Failed to fetch ourConversationId'
+      );
+    }
+    return conversationId;
+  }
+
   /**
    * Given a UUID and/or an E164, resolves to a string representing the local
    * database id of the given contact. In high trust mode, it may create new contacts,
@@ -713,7 +730,30 @@ export class ConversationController {
           ConversationCollection: window.Whisper.ConversationCollection,
         });
 
-        this._conversations.add(collection.models);
+        // Get rid of temporary conversations
+        const temporaryConversations = collection.filter(conversation =>
+          Boolean(conversation.get('isTemporary'))
+        );
+
+        if (temporaryConversations.length) {
+          window.log.warn(
+            `ConversationController: Removing ${temporaryConversations.length} temporary conversations`
+          );
+        }
+        const queue = new PQueue({ concurrency: 3, timeout: 1000 * 60 * 2 });
+        queue.addAll(
+          temporaryConversations.map(item => async () => {
+            await removeConversation(item.id, {
+              Conversation: window.Whisper.Conversation,
+            });
+          })
+        );
+        await queue.onIdle();
+
+        // Hydrate the final set of conversations
+        this._conversations.add(
+          collection.filter(conversation => !conversation.get('isTemporary'))
+        );
 
         this._initialFetchComplete = true;
 
@@ -725,10 +765,6 @@ export class ConversationController {
                 updateConversation(conversation.attributes);
               }
 
-              if (!conversation.get('lastMessage')) {
-                await conversation.updateLastMessage();
-              }
-
               // In case a too-large draft was saved to the database
               const draft = conversation.get('draft');
               if (draft && draft.length > MAX_MESSAGE_BODY_LENGTH) {
diff --git a/ts/background.ts b/ts/background.ts
index a81ad678f..00dd60861 100644
--- a/ts/background.ts
+++ b/ts/background.ts
@@ -427,29 +427,102 @@ type WhatIsThis = import('./window.d').WhatIsThis;
         await window.Signal.Data.shutdown();
       },
 
-      showStickerPack: async (packId: string, key: string) => {
+      showStickerPack: (packId: string, key: string) => {
         // We can get these events even if the user has never linked this instance.
         if (!window.Signal.Util.Registration.everDone()) {
+          window.log.warn('showStickerPack: Not registered, returning early');
           return;
         }
+        if (window.isShowingModal) {
+          window.log.warn(
+            'showStickerPack: Already showing modal, returning early'
+          );
+          return;
+        }
+        try {
+          window.isShowingModal = true;
 
-        // Kick off the download
-        window.Signal.Stickers.downloadEphemeralPack(packId, key);
+          // Kick off the download
+          window.Signal.Stickers.downloadEphemeralPack(packId, key);
 
-        const props = {
-          packId,
-          onClose: async () => {
-            stickerPreviewModalView.remove();
-            await window.Signal.Stickers.removeEphemeralPack(packId);
+          const props = {
+            packId,
+            onClose: async () => {
+              window.isShowingModal = false;
+              stickerPreviewModalView.remove();
+              await window.Signal.Stickers.removeEphemeralPack(packId);
+            },
+          };
+
+          const stickerPreviewModalView = new window.Whisper.ReactWrapperView({
+            className: 'sticker-preview-modal-wrapper',
+            JSX: window.Signal.State.Roots.createStickerPreviewModal(
+              window.reduxStore,
+              props
+            ),
+          });
+        } catch (error) {
+          window.isShowingModal = false;
+          window.log.error(
+            'showStickerPack: Ran into an error!',
+            error && error.stack ? error.stack : error
+          );
+          const errorView = new window.Whisper.ReactWrapperView({
+            className: 'error-modal-wrapper',
+            Component: window.Signal.Components.ErrorModal,
+            props: {
+              onClose: () => {
+                errorView.remove();
+              },
+            },
+          });
+        }
+      },
+      showGroupViaLink: async (hash: string) => {
+        // We can get these events even if the user has never linked this instance.
+        if (!window.Signal.Util.Registration.everDone()) {
+          window.log.warn('showGroupViaLink: Not registered, returning early');
+          return;
+        }
+        if (window.isShowingModal) {
+          window.log.warn(
+            'showGroupViaLink: Already showing modal, returning early'
+          );
+          return;
+        }
+        try {
+          await window.Signal.Groups.joinViaLink(hash);
+        } catch (error) {
+          window.log.error(
+            'showGroupViaLink: Ran into an error!',
+            error && error.stack ? error.stack : error
+          );
+          const errorView = new window.Whisper.ReactWrapperView({
+            className: 'error-modal-wrapper',
+            Component: window.Signal.Components.ErrorModal,
+            props: {
+              title: window.i18n('GroupV2--join--general-join-failure--title'),
+              description: window.i18n('GroupV2--join--general-join-failure'),
+              onClose: () => {
+                errorView.remove();
+              },
+            },
+          });
+        }
+        window.isShowingModal = false;
+      },
+
+      unknownSignalLink: () => {
+        window.log.warn('unknownSignalLink: Showing error dialog');
+        const errorView = new window.Whisper.ReactWrapperView({
+          className: 'error-modal-wrapper',
+          Component: window.Signal.Components.ErrorModal,
+          props: {
+            description: window.i18n('unknown-sgnl-link'),
+            onClose: () => {
+              errorView.remove();
+            },
           },
-        };
-
-        const stickerPreviewModalView = new window.Whisper.ReactWrapperView({
-          className: 'sticker-preview-modal-wrapper',
-          JSX: window.Signal.State.Roots.createStickerPreviewModal(
-            window.reduxStore,
-            props
-          ),
         });
       },
 
diff --git a/ts/components/Avatar.stories.tsx b/ts/components/Avatar.stories.tsx
index 8e9bc6123..65ce07ece 100644
--- a/ts/components/Avatar.stories.tsx
+++ b/ts/components/Avatar.stories.tsx
@@ -38,6 +38,7 @@ const createProps = (overrideProps: Partial<Props> = {}): Props => ({
     overrideProps.conversationType || 'direct'
   ),
   i18n,
+  loading: boolean('loading', overrideProps.loading || false),
   name: text('name', overrideProps.name || ''),
   noteToSelf: boolean('noteToSelf', overrideProps.noteToSelf || false),
   onClick: action('onClick'),
@@ -46,7 +47,7 @@ const createProps = (overrideProps: Partial<Props> = {}): Props => ({
   title: '',
 });
 
-const sizes: Array<Props['size']> = [112, 80, 52, 32, 28];
+const sizes: Array<Props['size']> = [112, 96, 80, 52, 32, 28];
 
 story.add('Avatar', () => {
   const props = createProps({
@@ -124,3 +125,11 @@ story.add('Broken Avatar for Group', () => {
 
   return sizes.map(size => <Avatar key={size} {...props} size={size} />);
 });
+
+story.add('Loading', () => {
+  const props = createProps({
+    loading: true,
+  });
+
+  return sizes.map(size => <Avatar key={size} {...props} size={size} />);
+});
diff --git a/ts/components/Avatar.tsx b/ts/components/Avatar.tsx
index c652b24fc..c78fefe07 100644
--- a/ts/components/Avatar.tsx
+++ b/ts/components/Avatar.tsx
@@ -4,6 +4,8 @@
 import * as React from 'react';
 import classNames from 'classnames';
 
+import { Spinner } from './Spinner';
+
 import { getInitials } from '../util/getInitials';
 import { LocalizerType } from '../types/Util';
 import { ColorType } from '../types/Colors';
@@ -20,6 +22,7 @@ export enum AvatarSize {
 export type Props = {
   avatarPath?: string;
   color?: ColorType;
+  loading?: boolean;
 
   conversationType: 'group' | 'direct';
   noteToSelf?: boolean;
@@ -136,11 +139,27 @@ export class Avatar extends React.Component<Props, State> {
     );
   }
 
+  public renderLoading(): JSX.Element {
+    const { size } = this.props;
+    const svgSize = size < 40 ? 'small' : 'normal';
+
+    return (
+      <div className="module-avatar__spinner-container">
+        <Spinner
+          size={`${size - 8}px`}
+          svgSize={svgSize}
+          direction="on-avatar"
+        />
+      </div>
+    );
+  }
+
   public render(): JSX.Element {
     const {
       avatarPath,
       color,
       innerRef,
+      loading,
       noteToSelf,
       onClick,
       size,
@@ -156,7 +175,9 @@ export class Avatar extends React.Component<Props, State> {
 
     let contents;
 
-    if (onClick) {
+    if (loading) {
+      contents = this.renderLoading();
+    } else if (onClick) {
       contents = (
         <button
           type="button"
diff --git a/ts/components/CompositionArea.stories.tsx b/ts/components/CompositionArea.stories.tsx
index 4732f944f..da16ca29c 100644
--- a/ts/components/CompositionArea.stories.tsx
+++ b/ts/components/CompositionArea.stories.tsx
@@ -71,6 +71,8 @@ const createProps = (overrideProps: Partial<Props> = {}): Props => ({
   title: '',
   // GroupV1 Disabled Actions
   onStartGroupMigration: action('onStartGroupMigration'),
+  // GroupV2 Pending Approval Actions
+  onCancelJoinRequest: action('onCancelJoinRequest'),
 });
 
 story.add('Default', () => {
diff --git a/ts/components/CompositionArea.tsx b/ts/components/CompositionArea.tsx
index ba89741fe..5c4fbe899 100644
--- a/ts/components/CompositionArea.tsx
+++ b/ts/components/CompositionArea.tsx
@@ -22,6 +22,10 @@ import {
   GroupV1DisabledActions,
   PropsType as GroupV1DisabledActionsPropsType,
 } from './conversation/GroupV1DisabledActions';
+import {
+  GroupV2PendingApprovalActions,
+  PropsType as GroupV2PendingApprovalActionsPropsType,
+} from './conversation/GroupV2PendingApprovalActions';
 import { MandatoryProfileSharingActions } from './conversation/MandatoryProfileSharingActions';
 import { countStickers } from './stickers/lib';
 import { LocalizerType } from '../types/Util';
@@ -30,6 +34,7 @@ import { EmojiPickDataType } from './emoji/EmojiPicker';
 export type OwnProps = {
   readonly i18n: LocalizerType;
   readonly areWePending?: boolean;
+  readonly areWePendingApproval?: boolean;
   readonly groupVersion?: 1 | 2;
   readonly isGroupV1AndDisabled?: boolean;
   readonly isMissingMandatoryProfileSharing?: boolean;
@@ -84,6 +89,7 @@ export type Props = Pick<
   > &
   MessageRequestActionsProps &
   Pick<GroupV1DisabledActionsPropsType, 'onStartGroupMigration'> &
+  Pick<GroupV2PendingApprovalActionsPropsType, 'onCancelJoinRequest'> &
   OwnProps;
 
 const emptyElement = (el: HTMLElement) => {
@@ -128,6 +134,7 @@ export const CompositionArea = ({
   // Message Requests
   acceptedMessageRequest,
   areWePending,
+  areWePendingApproval,
   conversationType,
   groupVersion,
   isBlocked,
@@ -146,6 +153,8 @@ export const CompositionArea = ({
   // GroupV1 Disabled Actions
   isGroupV1AndDisabled,
   onStartGroupMigration,
+  // GroupV2 Pending Approval Actions
+  onCancelJoinRequest,
 }: Props): JSX.Element => {
   const [disabled, setDisabled] = React.useState(false);
   const [showMic, setShowMic] = React.useState(!draftText);
@@ -403,6 +412,15 @@ export const CompositionArea = ({
     );
   }
 
+  if (areWePendingApproval) {
+    return (
+      <GroupV2PendingApprovalActions
+        i18n={i18n}
+        onCancelJoinRequest={onCancelJoinRequest}
+      />
+    );
+  }
+
   return (
     <div className="module-composition-area">
       <div className="module-composition-area__toggle-large">
diff --git a/ts/components/ErrorModal.tsx b/ts/components/ErrorModal.tsx
index e56ec2c54..7b57e5eb5 100644
--- a/ts/components/ErrorModal.tsx
+++ b/ts/components/ErrorModal.tsx
@@ -7,9 +7,9 @@ import { LocalizerType } from '../types/Util';
 import { ConfirmationModal } from './ConfirmationModal';
 
 export type PropsType = {
-  buttonText: string;
-  description: string;
-  title: string;
+  buttonText?: string;
+  description?: string;
+  title?: string;
 
   onClose: () => void;
   i18n: LocalizerType;
diff --git a/ts/components/GroupV1MigrationDialog.tsx b/ts/components/GroupV1MigrationDialog.tsx
index 5c57830eb..6fd3aed1d 100644
--- a/ts/components/GroupV1MigrationDialog.tsx
+++ b/ts/components/GroupV1MigrationDialog.tsx
@@ -8,12 +8,6 @@ import { ConversationType } from '../state/ducks/conversations';
 import { Avatar } from './Avatar';
 import { sortByTitle } from '../util/sortByTitle';
 
-export type ActionSpec = {
-  text: string;
-  action: () => unknown;
-  style?: 'affirmative' | 'negative';
-};
-
 type CallbackType = () => unknown;
 
 export type DataPropsType = {
diff --git a/ts/components/GroupV2JoinDialog.stories.tsx b/ts/components/GroupV2JoinDialog.stories.tsx
new file mode 100644
index 000000000..c76fd9db2
--- /dev/null
+++ b/ts/components/GroupV2JoinDialog.stories.tsx
@@ -0,0 +1,80 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import * as React from 'react';
+import { storiesOf } from '@storybook/react';
+import { boolean, number, text } from '@storybook/addon-knobs';
+import { action } from '@storybook/addon-actions';
+
+import { GroupV2JoinDialog, PropsType } from './GroupV2JoinDialog';
+import { setup as setupI18n } from '../../js/modules/i18n';
+import enMessages from '../../_locales/en/messages.json';
+
+const i18n = setupI18n('en', enMessages);
+
+const createProps = (overrideProps: Partial<PropsType> = {}): PropsType => ({
+  memberCount: number('memberCount', overrideProps.memberCount || 12),
+  avatar: overrideProps.avatar,
+  title: text('title', overrideProps.title || 'Random Group!'),
+  approvalRequired: boolean(
+    'approvalRequired',
+    overrideProps.approvalRequired || false
+  ),
+  join: action('join'),
+  onClose: action('onClose'),
+  i18n,
+});
+
+const stories = storiesOf('Components/GroupV2JoinDialog', module);
+
+stories.add('Basic', () => {
+  return <GroupV2JoinDialog {...createProps()} />;
+});
+
+stories.add('Approval required', () => {
+  return (
+    <GroupV2JoinDialog
+      {...createProps({
+        approvalRequired: true,
+        title: 'Approval required!',
+      })}
+    />
+  );
+});
+
+stories.add('With avatar', () => {
+  return (
+    <GroupV2JoinDialog
+      {...createProps({
+        avatar: {
+          url: '/fixtures/giphy-GVNvOUpeYmI7e.gif',
+        },
+        title: 'Has an avatar!',
+      })}
+    />
+  );
+});
+
+stories.add('With one member', () => {
+  return (
+    <GroupV2JoinDialog
+      {...createProps({
+        memberCount: 1,
+        title: 'Just one member!',
+      })}
+    />
+  );
+});
+
+stories.add('Avatar loading state', () => {
+  return (
+    <GroupV2JoinDialog
+      {...createProps({
+        avatar: {
+          loading: true,
+        },
+        title: 'Avatar loading!',
+      })}
+    />
+  );
+});
diff --git a/ts/components/GroupV2JoinDialog.tsx b/ts/components/GroupV2JoinDialog.tsx
new file mode 100644
index 000000000..d89aa7ff4
--- /dev/null
+++ b/ts/components/GroupV2JoinDialog.tsx
@@ -0,0 +1,120 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import * as React from 'react';
+import classNames from 'classnames';
+import { LocalizerType } from '../types/Util';
+import { Avatar } from './Avatar';
+import { Spinner } from './Spinner';
+
+import { PreJoinConversationType } from '../state/ducks/conversations';
+
+type CallbackType = () => unknown;
+
+export type DataPropsType = PreJoinConversationType & {
+  readonly join: CallbackType;
+  readonly onClose: CallbackType;
+};
+
+export type HousekeepingPropsType = {
+  readonly i18n: LocalizerType;
+};
+
+export type PropsType = DataPropsType & HousekeepingPropsType;
+
+function focusRef(el: HTMLElement | null) {
+  if (el) {
+    el.focus();
+  }
+}
+
+export const GroupV2JoinDialog = React.memo((props: PropsType) => {
+  const [isWorking, setIsWorking] = React.useState(false);
+  const [isJoining, setIsJoining] = React.useState(false);
+  const {
+    approvalRequired,
+    avatar,
+    i18n,
+    join,
+    memberCount,
+    onClose,
+    title,
+  } = props;
+
+  const joinString = approvalRequired
+    ? i18n('GroupV2--join--request-to-join-button')
+    : i18n('GroupV2--join--join-button');
+  const promptString = approvalRequired
+    ? i18n('GroupV2--join--prompt-with-approval')
+    : i18n('GroupV2--join--prompt');
+  const memberString =
+    memberCount === 1
+      ? i18n('GroupV2--join--member-count--single')
+      : i18n('GroupV2--join--member-count--multiple', {
+          count: memberCount.toString(),
+        });
+
+  const wrappedJoin = React.useCallback(() => {
+    setIsWorking(true);
+    setIsJoining(true);
+    join();
+  }, [join, setIsJoining, setIsWorking]);
+
+  const wrappedClose = React.useCallback(() => {
+    setIsWorking(true);
+    onClose();
+  }, [onClose, setIsWorking]);
+
+  return (
+    <div className="module-group-v2-join-dialog">
+      <button
+        aria-label={i18n('close')}
+        type="button"
+        disabled={isWorking}
+        className="module-group-v2-join-dialog__close-button"
+        onClick={wrappedClose}
+      />
+      <div className="module-group-v2-join-dialog__avatar">
+        <Avatar
+          avatarPath={avatar ? avatar.url : undefined}
+          loading={avatar && !avatar.url}
+          conversationType="group"
+          title={title}
+          size={80}
+          i18n={i18n}
+        />
+      </div>
+      <div className="module-group-v2-join-dialog__title">{title}</div>
+      <div className="module-group-v2-join-dialog__metadata">
+        {i18n('GroupV2--join--group-metadata', [memberString])}
+      </div>
+      <div className="module-group-v2-join-dialog__prompt">{promptString}</div>
+      <div className="module-group-v2-join-dialog__buttons">
+        <button
+          className={classNames(
+            'module-group-v2-join-dialog__button',
+            'module-group-v2-join-dialog__button--secondary'
+          )}
+          disabled={isWorking}
+          type="button"
+          onClick={wrappedClose}
+        >
+          {i18n('cancel')}
+        </button>
+        <button
+          className="module-group-v2-join-dialog__button"
+          disabled={isWorking}
+          ref={focusRef}
+          type="button"
+          onClick={wrappedJoin}
+        >
+          {isJoining ? (
+            <Spinner size="20px" svgSize="small" direction="on-avatar" />
+          ) : (
+            joinString
+          )}
+        </button>
+      </div>
+    </div>
+  );
+});
diff --git a/ts/components/Spinner.tsx b/ts/components/Spinner.tsx
index d176cd62a..2e63c1dc2 100644
--- a/ts/components/Spinner.tsx
+++ b/ts/components/Spinner.tsx
@@ -12,6 +12,7 @@ export const SpinnerDirections = [
   'incoming',
   'on-background',
   'on-progress-dialog',
+  'on-avatar',
 ] as const;
 export type SpinnerDirection = typeof SpinnerDirections[number];
 
diff --git a/ts/components/conversation/GroupV2PendingApprovalActions.stories.tsx b/ts/components/conversation/GroupV2PendingApprovalActions.stories.tsx
new file mode 100644
index 000000000..377c88313
--- /dev/null
+++ b/ts/components/conversation/GroupV2PendingApprovalActions.stories.tsx
@@ -0,0 +1,29 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import * as React from 'react';
+import { storiesOf } from '@storybook/react';
+import { action } from '@storybook/addon-actions';
+
+import {
+  GroupV2PendingApprovalActions,
+  PropsType as GroupV2PendingApprovalActionsPropsType,
+} from './GroupV2PendingApprovalActions';
+import { setup as setupI18n } from '../../../js/modules/i18n';
+import enMessages from '../../../_locales/en/messages.json';
+
+const i18n = setupI18n('en', enMessages);
+
+const createProps = (): GroupV2PendingApprovalActionsPropsType => ({
+  i18n,
+  onCancelJoinRequest: action('onCancelJoinRequest'),
+});
+
+const stories = storiesOf(
+  'Components/Conversation/GroupV2PendingApprovalActions',
+  module
+);
+
+stories.add('Default', () => {
+  return <GroupV2PendingApprovalActions {...createProps()} />;
+});
diff --git a/ts/components/conversation/GroupV2PendingApprovalActions.tsx b/ts/components/conversation/GroupV2PendingApprovalActions.tsx
new file mode 100644
index 000000000..52611164f
--- /dev/null
+++ b/ts/components/conversation/GroupV2PendingApprovalActions.tsx
@@ -0,0 +1,33 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import * as React from 'react';
+import { LocalizerType } from '../../types/Util';
+
+export type PropsType = {
+  i18n: LocalizerType;
+  onCancelJoinRequest: () => unknown;
+};
+
+export const GroupV2PendingApprovalActions = ({
+  i18n,
+  onCancelJoinRequest,
+}: PropsType): JSX.Element => {
+  return (
+    <div className="module-group-v2-pending-approval-actions">
+      <p className="module-group-v2-pending-approval-actions__message">
+        {i18n('GroupV2--join--requested')}
+      </p>
+      <div className="module-group-v2-pending-approval-actions__buttons">
+        <button
+          type="button"
+          onClick={onCancelJoinRequest}
+          tabIndex={0}
+          className="module-group-v2-pending-approval-actions__buttons__button"
+        >
+          {i18n('GroupV2--join--cancel-request-to-join')}
+        </button>
+      </div>
+    </div>
+  );
+};
diff --git a/ts/groups.ts b/ts/groups.ts
index 658d80a36..ad3ee6dc9 100644
--- a/ts/groups.ts
+++ b/ts/groups.ts
@@ -19,6 +19,7 @@ import {
   maybeFetchNewCredentials,
 } from './services/groupCredentialFetcher';
 import dataInterface from './sql/Client';
+import { toWebSafeBase64, fromWebSafeBase64 } from './util/webSafeBase64';
 import {
   ConversationAttributesType,
   GroupV2MemberType,
@@ -57,6 +58,7 @@ import {
   GroupChangeClass,
   GroupChangesClass,
   GroupClass,
+  GroupJoinInfoClass,
   MemberClass,
   MemberPendingAdminApprovalClass,
   MemberPendingProfileKeyClass,
@@ -71,6 +73,8 @@ import MessageSender, { CallbackResultType } from './textsecure/SendMessage';
 import { CURRENT_SCHEMA_VERSION as MAX_MESSAGE_SCHEMA } from '../js/modules/types/message';
 import { ConversationModel } from './models/conversations';
 
+export { joinViaLink } from './groups/joinViaLink';
+
 export type GroupV2AccessCreateChangeType = {
   type: 'create';
 };
@@ -227,6 +231,7 @@ const TEMPORAL_AUTH_REJECTED_CODE = 401;
 const GROUP_ACCESS_DENIED_CODE = 403;
 const GROUP_NONEXISTENT_CODE = 404;
 const SUPPORTED_CHANGE_EPOCH = 1;
+export const LINK_VERSION_ERROR = 'LINK_VERSION_ERROR';
 const GROUP_INVITE_LINK_PASSWORD_LENGTH = 16;
 
 // Group Links
@@ -235,8 +240,23 @@ export function generateGroupInviteLinkPassword(): ArrayBuffer {
   return getRandomBytes(GROUP_INVITE_LINK_PASSWORD_LENGTH);
 }
 
-export function toWebSafeBase64(base64: string): string {
-  return base64.replace(/\//g, '_').replace(/\+/g, '-').replace(/=/g, '');
+// Group Links
+
+export async function getPreJoinGroupInfo(
+  inviteLinkPasswordBase64: string,
+  masterKeyBase64: string
+): Promise<GroupJoinInfoClass> {
+  const data = window.Signal.Groups.deriveGroupFields(
+    base64ToArrayBuffer(masterKeyBase64)
+  );
+
+  return makeRequestWithTemporalRetry({
+    logId: `groupv2(${data.id})`,
+    publicParams: arrayBufferToBase64(data.publicParams),
+    secretParams: arrayBufferToBase64(data.secretParams),
+    request: (sender, options) =>
+      sender.getGroupFromLink(inviteLinkPasswordBase64, options),
+  });
 }
 
 export function buildGroupLink(conversation: ConversationModel): string {
@@ -257,6 +277,51 @@ export function buildGroupLink(conversation: ConversationModel): string {
   return `sgnl://signal.group/#${hash}`;
 }
 
+export function parseGroupLink(
+  hash: string
+): { masterKey: string; inviteLinkPassword: string } {
+  const base64 = fromWebSafeBase64(hash);
+  const buffer = base64ToArrayBuffer(base64);
+
+  const inviteLinkProto = window.textsecure.protobuf.GroupInviteLink.decode(
+    buffer
+  );
+  if (
+    inviteLinkProto.contents !== 'v1Contents' ||
+    !inviteLinkProto.v1Contents
+  ) {
+    const error = new Error(
+      'parseGroupLink: Parsed proto is missing v1Contents'
+    );
+    error.name = LINK_VERSION_ERROR;
+    throw error;
+  }
+
+  if (!hasData(inviteLinkProto.v1Contents.groupMasterKey)) {
+    throw new Error('v1Contents.groupMasterKey had no data!');
+  }
+  if (!hasData(inviteLinkProto.v1Contents.inviteLinkPassword)) {
+    throw new Error('v1Contents.inviteLinkPassword had no data!');
+  }
+
+  const masterKey: string = inviteLinkProto.v1Contents.groupMasterKey.toString(
+    'base64'
+  );
+  if (masterKey.length !== 44) {
+    throw new Error(`masterKey had unexpected length ${masterKey.length}`);
+  }
+  const inviteLinkPassword: string = inviteLinkProto.v1Contents.inviteLinkPassword.toString(
+    'base64'
+  );
+  if (inviteLinkPassword.length === 0) {
+    throw new Error(
+      `inviteLinkPassword had unexpected length ${inviteLinkPassword.length}`
+    );
+  }
+
+  return { masterKey, inviteLinkPassword };
+}
+
 // Group Modifications
 
 async function uploadAvatar({
@@ -596,6 +661,84 @@ export function buildDeletePendingAdminApprovalMemberChange({
   return actions;
 }
 
+export function buildAddPendingAdminApprovalMemberChange({
+  group,
+  profileKeyCredentialBase64,
+  serverPublicParamsBase64,
+}: {
+  group: ConversationAttributesType;
+  profileKeyCredentialBase64: string;
+  serverPublicParamsBase64: string;
+}): GroupChangeClass.Actions {
+  const actions = new window.textsecure.protobuf.GroupChange.Actions();
+
+  if (!group.secretParams) {
+    throw new Error(
+      'buildAddPendingAdminApprovalMemberChange: group was missing secretParams!'
+    );
+  }
+  const clientZkProfileCipher = getClientZkProfileOperations(
+    serverPublicParamsBase64
+  );
+
+  const addMemberPendingAdminApproval = new window.textsecure.protobuf.GroupChange.Actions.AddMemberPendingAdminApprovalAction();
+  const presentation = createProfileKeyCredentialPresentation(
+    clientZkProfileCipher,
+    profileKeyCredentialBase64,
+    group.secretParams
+  );
+
+  const added = new window.textsecure.protobuf.MemberPendingAdminApproval();
+  added.presentation = presentation;
+
+  addMemberPendingAdminApproval.added = added;
+
+  actions.version = (group.revision || 0) + 1;
+  actions.addMemberPendingAdminApprovals = [addMemberPendingAdminApproval];
+
+  return actions;
+}
+
+export function buildAddMember({
+  group,
+  profileKeyCredentialBase64,
+  serverPublicParamsBase64,
+}: {
+  group: ConversationAttributesType;
+  profileKeyCredentialBase64: string;
+  serverPublicParamsBase64: string;
+  joinFromInviteLink?: boolean;
+}): GroupChangeClass.Actions {
+  const MEMBER_ROLE_ENUM = window.textsecure.protobuf.Member.Role;
+
+  const actions = new window.textsecure.protobuf.GroupChange.Actions();
+
+  if (!group.secretParams) {
+    throw new Error('buildAddMember: group was missing secretParams!');
+  }
+  const clientZkProfileCipher = getClientZkProfileOperations(
+    serverPublicParamsBase64
+  );
+
+  const addMember = new window.textsecure.protobuf.GroupChange.Actions.AddMemberAction();
+  const presentation = createProfileKeyCredentialPresentation(
+    clientZkProfileCipher,
+    profileKeyCredentialBase64,
+    group.secretParams
+  );
+
+  const added = new window.textsecure.protobuf.Member();
+  added.presentation = presentation;
+  added.role = MEMBER_ROLE_ENUM.DEFAULT;
+
+  addMember.added = added;
+
+  actions.version = (group.revision || 0) + 1;
+  actions.addMembers = [addMember];
+
+  return actions;
+}
+
 export function buildDeletePendingMemberChange({
   uuids,
   group,
@@ -744,11 +887,13 @@ export function buildPromoteMemberChange({
 export async function uploadGroupChange({
   actions,
   group,
+  inviteLinkPassword,
 }: {
   actions: GroupChangeClass.Actions;
   group: ConversationAttributesType;
+  inviteLinkPassword?: string;
 }): Promise<GroupChangeClass> {
-  const logId = idForLogging(group);
+  const logId = idForLogging(group.groupId);
 
   // Ensure we have the credentials we need before attempting GroupsV2 operations
   await maybeFetchNewCredentials();
@@ -764,14 +909,160 @@ export async function uploadGroupChange({
     logId: `uploadGroupChange/${logId}`,
     publicParams: group.publicParams,
     secretParams: group.secretParams,
-    request: (sender, options) => sender.modifyGroup(actions, options),
+    request: (sender, options) =>
+      sender.modifyGroup(actions, options, inviteLinkPassword),
   });
 }
 
+export async function modifyGroupV2({
+  conversation,
+  createGroupChange,
+  inviteLinkPassword,
+  name,
+}: {
+  conversation: ConversationModel;
+  createGroupChange: () => Promise<GroupChangeClass.Actions | undefined>;
+  inviteLinkPassword?: string;
+  name: string;
+}): Promise<void> {
+  const idLog = `${name}/${conversation.idForLogging()}`;
+
+  if (!conversation.isGroupV2()) {
+    throw new Error(
+      `modifyGroupV2/${idLog}: Called for non-GroupV2 conversation`
+    );
+  }
+
+  const ONE_MINUTE = 1000 * 60;
+  const startTime = Date.now();
+  const timeoutTime = startTime + ONE_MINUTE;
+
+  const MAX_ATTEMPTS = 5;
+
+  for (let attempt = 0; attempt < MAX_ATTEMPTS; attempt += 1) {
+    window.log.info(`modifyGroupV2/${idLog}: Starting attempt ${attempt}`);
+    try {
+      // eslint-disable-next-line no-await-in-loop
+      await window.waitForEmptyEventQueue();
+
+      window.log.info(`modifyGroupV2/${idLog}: Queuing attempt ${attempt}`);
+
+      // eslint-disable-next-line no-await-in-loop
+      await conversation.queueJob(async () => {
+        window.log.info(`modifyGroupV2/${idLog}: Running attempt ${attempt}`);
+
+        const actions = await createGroupChange();
+        if (!actions) {
+          window.log.warn(
+            `modifyGroupV2/${idLog}: No change actions. Returning early.`
+          );
+          return;
+        }
+
+        // The new revision has to be exactly one more than the current revision
+        //   or it won't upload properly, and it won't apply in maybeUpdateGroup
+        const currentRevision = conversation.get('revision');
+        const newRevision = actions.version;
+
+        if ((currentRevision || 0) + 1 !== newRevision) {
+          throw new Error(
+            `modifyGroupV2/${idLog}: Revision mismatch - ${currentRevision} to ${newRevision}.`
+          );
+        }
+
+        // Upload. If we don't have permission, the server will return an error here.
+        const groupChange = await window.Signal.Groups.uploadGroupChange({
+          actions,
+          inviteLinkPassword,
+          group: conversation.attributes,
+        });
+
+        const groupChangeBuffer = groupChange.toArrayBuffer();
+        const groupChangeBase64 = arrayBufferToBase64(groupChangeBuffer);
+
+        // Apply change locally, just like we would with an incoming change. This will
+        //   change conversation state and add change notifications to the timeline.
+        await window.Signal.Groups.maybeUpdateGroup({
+          conversation,
+          groupChangeBase64,
+          newRevision,
+        });
+
+        // Send message to notify group members (including pending members) of change
+        const profileKey = conversation.get('profileSharing')
+          ? window.storage.get('profileKey')
+          : undefined;
+
+        const sendOptions = conversation.getSendOptions();
+        const timestamp = Date.now();
+
+        const promise = conversation.wrapSend(
+          window.textsecure.messaging.sendMessageToGroup(
+            {
+              groupV2: conversation.getGroupV2Info({
+                groupChange: groupChangeBuffer,
+                includePendingMembers: true,
+              }),
+              timestamp,
+              profileKey,
+            },
+            sendOptions
+          )
+        );
+
+        // We don't save this message; we just use it to ensure that a sync message is
+        //   sent to our linked devices.
+        const m = new window.Whisper.Message(({
+          conversationId: conversation.id,
+          type: 'not-to-save',
+          sent_at: timestamp,
+          received_at: timestamp,
+          // TODO: DESKTOP-722
+          // this type does not fully implement the interface it is expected to
+        } as unknown) as MessageAttributesType);
+
+        // This is to ensure that the functions in send() and sendSyncMessage()
+        //   don't save anything to the database.
+        m.doNotSave = true;
+
+        await m.send(promise);
+      });
+
+      // If we've gotten here with no error, we exit!
+      window.log.info(
+        `modifyGroupV2/${idLog}: Update complete, with attempt ${attempt}!`
+      );
+      break;
+    } catch (error) {
+      if (error.code === 409 && Date.now() <= timeoutTime) {
+        window.log.info(
+          `modifyGroupV2/${idLog}: Conflict while updating. Trying again...`
+        );
+
+        // eslint-disable-next-line no-await-in-loop
+        await conversation.fetchLatestGroupV2Data();
+      } else if (error.code === 409) {
+        window.log.error(
+          `modifyGroupV2/${idLog}: Conflict while updating. Timed out; not retrying.`
+        );
+        // We don't wait here because we're breaking out of the loop immediately.
+        conversation.fetchLatestGroupV2Data();
+        throw error;
+      } else {
+        const errorString = error && error.stack ? error.stack : error;
+        window.log.error(
+          `modifyGroupV2/${idLog}: Error updating: ${errorString}`
+        );
+        throw error;
+      }
+    }
+  }
+}
+
 // Utility
 
-function idForLogging(group: ConversationAttributesType) {
-  return `groupv2(${group.groupId})`;
+export function idForLogging(groupId: string | undefined): string {
+  return `groupv2(${groupId})`;
 }
 
 export function deriveGroupFields(
@@ -1242,6 +1533,7 @@ export async function initiateMigrationToGroupV2(
         accessControl: {
           attributes: ACCESS_ENUM.MEMBER,
           members: ACCESS_ENUM.MEMBER,
+          addFromInviteLink: ACCESS_ENUM.UNSATISFIABLE,
         },
         membersV2,
         pendingMembersV2,
@@ -1437,6 +1729,128 @@ export async function waitThenRespondToGroupV2Migration(
   });
 }
 
+export function buildMigrationBubble(
+  previousGroupV1MembersIds: Array<string>,
+  newAttributes: ConversationAttributesType
+): MessageAttributesType {
+  const ourConversationId = window.ConversationController.getOurConversationIdOrThrow();
+
+  // Assemble items to commemorate this event for the timeline..
+  const combinedConversationIds: Array<string> = [
+    ...(newAttributes.membersV2 || []).map(item => item.conversationId),
+    ...(newAttributes.pendingMembersV2 || []).map(item => item.conversationId),
+  ];
+  const droppedMemberIds: Array<string> = difference(
+    previousGroupV1MembersIds,
+    combinedConversationIds
+  ).filter(id => id && id !== ourConversationId);
+  const invitedMembers = (newAttributes.pendingMembersV2 || []).filter(
+    item => item.conversationId !== ourConversationId
+  );
+
+  const areWeInvited = (newAttributes.pendingMembersV2 || []).some(
+    item => item.conversationId === ourConversationId
+  );
+
+  return {
+    ...generateBasicMessage(),
+    type: 'group-v1-migration',
+    groupMigration: {
+      areWeInvited,
+      invitedMembers,
+      droppedMemberIds,
+    },
+  };
+}
+
+export async function joinGroupV2ViaLinkAndMigrate({
+  approvalRequired,
+  conversation,
+  inviteLinkPassword,
+  revision,
+}: {
+  approvalRequired: boolean;
+  conversation: ConversationModel;
+  inviteLinkPassword: string;
+  revision: number;
+}): Promise<void> {
+  const isGroupV1 = conversation.isGroupV1();
+  const previousGroupV1Id = conversation.get('groupId');
+
+  if (!isGroupV1 || !previousGroupV1Id) {
+    throw new Error(
+      `joinGroupV2ViaLinkAndMigrate: Conversation is not GroupV1! ${conversation.idForLogging()}`
+    );
+  }
+
+  // Derive GroupV2 fields
+  const groupV1IdBuffer = fromEncodedBinaryToArrayBuffer(previousGroupV1Id);
+  const masterKeyBuffer = await deriveMasterKeyFromGroupV1(groupV1IdBuffer);
+  const fields = deriveGroupFields(masterKeyBuffer);
+
+  const groupId = arrayBufferToBase64(fields.id);
+  const logId = idForLogging(groupId);
+  window.log.info(
+    `joinGroupV2ViaLinkAndMigrate/${logId}: Migrating from ${conversation.idForLogging()}`
+  );
+
+  const masterKey = arrayBufferToBase64(masterKeyBuffer);
+  const secretParams = arrayBufferToBase64(fields.secretParams);
+  const publicParams = arrayBufferToBase64(fields.publicParams);
+
+  // A mini-migration, which will not show dropped/invited members
+  const newAttributes = {
+    ...conversation.attributes,
+
+    // Core GroupV2 info
+    revision,
+    groupId,
+    groupVersion: 2,
+    masterKey,
+    publicParams,
+    secretParams,
+    groupInviteLinkPassword: inviteLinkPassword,
+
+    left: true,
+
+    // Capture previous GroupV1 data for future use
+    previousGroupV1Id: conversation.get('groupId'),
+    previousGroupV1Members: conversation.get('members'),
+
+    // Clear storage ID, since we need to start over on the storage service
+    storageID: undefined,
+
+    // Clear obsolete data
+    derivedGroupV2Id: undefined,
+    members: undefined,
+  };
+  const groupChangeMessages = [
+    {
+      ...generateBasicMessage(),
+      type: 'group-v1-migration',
+      groupMigration: {
+        areWeInvited: false,
+        invitedMembers: [],
+        droppedMemberIds: [],
+      },
+    },
+  ];
+  await updateGroup({
+    conversation,
+    updates: {
+      newAttributes,
+      groupChangeMessages,
+      members: [],
+    },
+  });
+
+  // Now things are set up, so we can go through normal channels
+  await conversation.joinGroupV2ViaLink({
+    inviteLinkPassword,
+    approvalRequired,
+  });
+}
+
 // This may be called from storage service, an out-of-band check, or an incoming message.
 //   If this is kicked off via an incoming message, we want to do the right thing and hit
 //   the log endpoint - the parameters beyond conversation are needed in that scenario.
@@ -1459,17 +1873,11 @@ export async function respondToGroupV2Migration({
     );
   }
 
-  // If we were not previously a member, we won't migrate
-  const ourConversationId = window.ConversationController.getOurConversationId();
+  const ourConversationId = window.ConversationController.getOurConversationIdOrThrow();
   const wereWePreviouslyAMember =
     !conversation.get('left') &&
     ourConversationId &&
     conversation.hasMember(ourConversationId);
-  if (!ourConversationId) {
-    throw new Error(
-      `respondToGroupV2Migration: No conversationId when attempting to migrate ${conversation.idForLogging()}. Returning early.`
-    );
-  }
 
   // Derive GroupV2 fields
   const groupV1IdBuffer = fromEncodedBinaryToArrayBuffer(previousGroupV1Id);
@@ -1477,7 +1885,7 @@ export async function respondToGroupV2Migration({
   const fields = deriveGroupFields(masterKeyBuffer);
 
   const groupId = arrayBufferToBase64(fields.id);
-  const logId = `groupv2(${groupId})`;
+  const logId = idForLogging(groupId);
   window.log.info(
     `respondToGroupV2Migration/${logId}: Migrating from ${conversation.idForLogging()}`
   );
@@ -1600,17 +2008,11 @@ export async function respondToGroupV2Migration({
     groupState,
   });
 
-  // Assemble items to commemorate this event for the timeline..
-  const combinedConversationIds: Array<string> = [
-    ...(newAttributes.membersV2 || []).map(item => item.conversationId),
-    ...(newAttributes.pendingMembersV2 || []).map(item => item.conversationId),
-  ];
-  const droppedMemberIds: Array<string> = difference(
-    previousGroupV1MembersIds,
-    combinedConversationIds
-  ).filter(id => id && id !== ourConversationId);
-  const invitedMembers = (newAttributes.pendingMembersV2 || []).filter(
-    item => item.conversationId !== ourConversationId
+  // Generate notifications into the timeline
+  const groupChangeMessages: Array<MessageAttributesType> = [];
+
+  groupChangeMessages.push(
+    buildMigrationBubble(previousGroupV1MembersIds, newAttributes)
   );
 
   const areWeInvited = (newAttributes.pendingMembersV2 || []).some(
@@ -1619,19 +2021,6 @@ export async function respondToGroupV2Migration({
   const areWeMember = (newAttributes.membersV2 || []).some(
     item => item.conversationId === ourConversationId
   );
-
-  // Generate notifications into the timeline
-  const groupChangeMessages: Array<MessageAttributesType> = [];
-  groupChangeMessages.push({
-    ...generateBasicMessage(),
-    type: 'group-v1-migration',
-    groupMigration: {
-      areWeInvited,
-      invitedMembers,
-      droppedMemberIds,
-    },
-  });
-
   if (!areWeInvited && !areWeMember) {
     // Add a message to the timeline saying the user was removed. This shouldn't happen.
     groupChangeMessages.push({
@@ -1764,6 +2153,8 @@ async function updateGroup({
 
   const isInitialDataFetch =
     !isNumber(startingRevision) && isNumber(endingRevision);
+  const isInGroup = !updates.newAttributes.left;
+  const justJoinedGroup = conversation.get('left') && isInGroup;
 
   // Ensure that all generated messages are ordered properly.
   // Before the provided timestamp so update messages appear before the
@@ -1782,9 +2173,12 @@ async function updateGroup({
     //   fetched data about it, and we were able to fetch its name. Nobody likes to see
     //   Unknown Group in the left pane.
     active_at:
-      isInitialDataFetch && newAttributes.name
+      (isInitialDataFetch || justJoinedGroup) && newAttributes.name
         ? finalReceivedAt
         : newAttributes.active_at,
+    temporaryMemberCount: isInGroup
+      ? undefined
+      : newAttributes.temporaryMemberCount,
   });
 
   if (idChanged) {
@@ -1843,14 +2237,18 @@ async function getGroupUpdates({
   newRevision?: number;
   serverPublicParamsBase64: string;
 }): Promise<UpdatesResultType> {
-  const logId = idForLogging(group);
+  const logId = idForLogging(group.groupId);
 
   window.log.info(`getGroupUpdates/${logId}: Starting...`);
 
   const currentRevision = group.revision;
   const isFirstFetch = !isNumber(group.revision);
+  const ourConversationId = window.ConversationController.getOurConversationId();
 
   const isInitialCreationMessage = isFirstFetch && newRevision === 0;
+  const weAreAwaitingApproval = (group.pendingAdminApprovalV2 || []).find(
+    item => item.conversationId === ourConversationId
+  );
   const isOneVersionUp =
     isNumber(currentRevision) &&
     isNumber(newRevision) &&
@@ -1860,7 +2258,7 @@ async function getGroupUpdates({
     window.GV2_ENABLE_SINGLE_CHANGE_PROCESSING &&
     groupChangeBase64 &&
     isNumber(newRevision) &&
-    (isInitialCreationMessage || isOneVersionUp)
+    (isInitialCreationMessage || weAreAwaitingApproval || isOneVersionUp)
   ) {
     window.log.info(`getGroupUpdates/${logId}: Processing just one change`);
     const groupChangeBuffer = base64ToArrayBuffer(groupChangeBase64);
@@ -1872,7 +2270,12 @@ async function getGroupUpdates({
       groupChange.changeEpoch <= SUPPORTED_CHANGE_EPOCH;
 
     if (isChangeSupported) {
-      return integrateGroupChange({ group, newRevision, groupChange });
+      return updateGroupViaSingleChange({
+        group,
+        newRevision,
+        groupChange,
+        serverPublicParamsBase64,
+      });
     }
 
     window.log.info(
@@ -1933,7 +2336,7 @@ async function updateGroupViaState({
   group: ConversationAttributesType;
   serverPublicParamsBase64: string;
 }): Promise<UpdatesResultType> {
-  const logId = idForLogging(group);
+  const logId = idForLogging(group.groupId);
   const data = window.storage.get(GROUP_CREDENTIALS_KEY);
   if (!data) {
     throw new Error('updateGroupViaState: No group credentials!');
@@ -1980,6 +2383,46 @@ async function updateGroupViaState({
   }
 }
 
+async function updateGroupViaSingleChange({
+  group,
+  groupChange,
+  newRevision,
+  serverPublicParamsBase64,
+}: {
+  group: ConversationAttributesType;
+  groupChange: GroupChangeClass;
+  newRevision: number;
+  serverPublicParamsBase64: string;
+}): Promise<UpdatesResultType> {
+  const wasInGroup = !group.left;
+  const result: UpdatesResultType = await integrateGroupChange({
+    group,
+    groupChange,
+    newRevision,
+  });
+
+  const nowInGroup = !result.newAttributes.left;
+
+  // If we were just added to the group (for example, via a join link), we go fetch the
+  //   entire group state to make sure we're up to date.
+  if (!wasInGroup && nowInGroup) {
+    const { newAttributes, members } = await updateGroupViaState({
+      group: result.newAttributes,
+      serverPublicParamsBase64,
+    });
+
+    // We discard any change events that come out of this full group fetch, but we do
+    //   keep the final group attributes generated, as well as any new members.
+    return {
+      ...result,
+      members: [...result.members, ...members],
+      newAttributes,
+    };
+  }
+
+  return result;
+}
+
 async function updateGroupViaLogs({
   group,
   serverPublicParamsBase64,
@@ -1989,7 +2432,7 @@ async function updateGroupViaLogs({
   newRevision: number;
   serverPublicParamsBase64: string;
 }): Promise<UpdatesResultType> {
-  const logId = idForLogging(group);
+  const logId = idForLogging(group.groupId);
   const data = window.storage.get(GROUP_CREDENTIALS_KEY);
   if (!data) {
     throw new Error('getGroupUpdates: No group credentials!');
@@ -2032,10 +2475,10 @@ function generateBasicMessage() {
   } as MessageAttributesType;
 }
 
-function generateLeftGroupChanges(
+async function generateLeftGroupChanges(
   group: ConversationAttributesType
-): UpdatesResultType {
-  const logId = idForLogging(group);
+): Promise<UpdatesResultType> {
+  const logId = idForLogging(group.groupId);
   window.log.info(`generateLeftGroupChanges/${logId}: Starting...`);
   const ourConversationId = window.ConversationController.getOurConversationId();
   if (!ourConversationId) {
@@ -2043,6 +2486,29 @@ function generateLeftGroupChanges(
       'generateLeftGroupChanges: We do not have a conversationId!'
     );
   }
+
+  const { masterKey, groupInviteLinkPassword } = group;
+  let { revision } = group;
+
+  try {
+    if (masterKey && groupInviteLinkPassword) {
+      window.log.info(
+        `generateLeftGroupChanges/${logId}: Have invite link. Attempting to fetch latest revision with it.`
+      );
+      const preJoinInfo = await getPreJoinGroupInfo(
+        groupInviteLinkPassword,
+        masterKey
+      );
+
+      revision = preJoinInfo.version;
+    }
+  } catch (error) {
+    window.log.warn(
+      'generateLeftGroupChanges: Failed to fetch latest revision via group link. Code:',
+      error.code
+    );
+  }
+
   const existingMembers = group.membersV2 || [];
   const newAttributes: ConversationAttributesType = {
     ...group,
@@ -2050,6 +2516,7 @@ function generateLeftGroupChanges(
       member => member.conversationId !== ourConversationId
     ),
     left: true,
+    revision,
   };
   const isNewlyRemoved =
     existingMembers.length > (newAttributes.membersV2 || []).length;
@@ -2162,7 +2629,7 @@ async function integrateGroupChanges({
   newRevision: number;
   changes: Array<GroupChangesClass>;
 }): Promise<UpdatesResultType> {
-  const logId = idForLogging(group);
+  const logId = idForLogging(group.groupId);
   let attributes = group;
   const finalMessages: Array<Array<MessageAttributesType>> = [];
   const finalMembers: Array<Array<MemberType>> = [];
@@ -2258,7 +2725,7 @@ async function integrateGroupChange({
   groupState?: GroupClass;
   newRevision: number;
 }): Promise<UpdatesResultType> {
-  const logId = idForLogging(group);
+  const logId = idForLogging(group.groupId);
   if (!group.secretParams) {
     throw new Error(
       `integrateGroupChange/${logId}: Group was missing secretParams!`
@@ -2299,7 +2766,16 @@ async function integrateGroupChange({
     isNumber(group.revision) &&
     groupChangeActions.version > group.revision + 1;
 
-  if (!isChangeSupported || isFirstFetch || isMoreThanOneVersionUp) {
+  const ourConversationId = window.ConversationController.getOurConversationIdOrThrow();
+  const weAreAwaitingApproval = (group.pendingAdminApprovalV2 || []).find(
+    item => item.conversationId === ourConversationId
+  );
+
+  if (
+    !isChangeSupported ||
+    isFirstFetch ||
+    (isMoreThanOneVersionUp && !weAreAwaitingApproval)
+  ) {
     if (!groupState) {
       throw new Error(
         `integrateGroupChange/${logId}: No group state, but we can't apply changes!`
@@ -2372,7 +2848,7 @@ async function getCurrentGroupState({
   group: ConversationAttributesType;
   serverPublicParamsBase64: string;
 }): Promise<UpdatesResultType> {
-  const logId = idForLogging(group);
+  const logId = idForLogging(group.groupId);
   const sender = window.textsecure.messaging;
   if (!sender) {
     throw new Error('textsecure.messaging is not available!');
@@ -2425,7 +2901,7 @@ function extractDiffs({
   old: ConversationAttributesType;
   sourceConversationId?: string;
 }): Array<MessageAttributesType> {
-  const logId = idForLogging(old);
+  const logId = idForLogging(old.groupId);
   const details: Array<GroupV2ChangeDetailType> = [];
   const ourConversationId = window.ConversationController.getOurConversationId();
   const ACCESS_ENUM = window.textsecure.protobuf.AccessControl.AccessRequired;
@@ -2847,7 +3323,7 @@ async function applyGroupChange({
   group: ConversationAttributesType;
   sourceConversationId: string;
 }): Promise<GroupChangeResultType> {
-  const logId = idForLogging(group);
+  const logId = idForLogging(group.groupId);
   const ourConversationId = window.ConversationController.getOurConversationId();
 
   const ACCESS_ENUM = window.textsecure.protobuf.AccessControl.AccessRequired;
@@ -3335,11 +3811,11 @@ async function applyGroupChange({
 
 // Ovewriting result.avatar as part of functionality
 /* eslint-disable no-param-reassign */
-async function applyNewAvatar(
+export async function applyNewAvatar(
   newAvatar: string | undefined,
-  result: ConversationAttributesType,
+  result: Pick<ConversationAttributesType, 'avatar' | 'secretParams'>,
   logId: string
-) {
+): Promise<void> {
   try {
     // Avatar has been dropped
     if (!newAvatar && result.avatar) {
@@ -3413,7 +3889,7 @@ async function applyGroupState({
   groupState: GroupClass;
   sourceConversationId?: string;
 }): Promise<ConversationAttributesType> {
-  const logId = idForLogging(group);
+  const logId = idForLogging(group.groupId);
   const ACCESS_ENUM = window.textsecure.protobuf.AccessControl.AccessRequired;
   const MEMBER_ROLE_ENUM = window.textsecure.protobuf.Member.Role;
   const version = groupState.version || 0;
@@ -4144,6 +4620,24 @@ function decryptGroupChange(
   return actions;
 }
 
+export function decryptGroupTitle(
+  title: ProtoBinaryType,
+  secretParams: string
+): string | undefined {
+  const clientZkGroupCipher = getClientZkGroupCipher(secretParams);
+  if (hasData(title)) {
+    const blob = window.textsecure.protobuf.GroupAttributeBlob.decode(
+      decryptGroupBlob(clientZkGroupCipher, title.toArrayBuffer())
+    );
+
+    if (blob && blob.content === 'title') {
+      return blob.title;
+    }
+  }
+
+  return undefined;
+}
+
 function decryptGroupState(
   groupState: GroupClass,
   groupSecretParams: string,
diff --git a/ts/groups/joinViaLink.ts b/ts/groups/joinViaLink.ts
new file mode 100644
index 000000000..f2bcb75e8
--- /dev/null
+++ b/ts/groups/joinViaLink.ts
@@ -0,0 +1,423 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import {
+  applyNewAvatar,
+  decryptGroupTitle,
+  deriveGroupFields,
+  getPreJoinGroupInfo,
+  idForLogging,
+  LINK_VERSION_ERROR,
+  parseGroupLink,
+} from '../groups';
+import { arrayBufferToBase64, base64ToArrayBuffer } from '../Crypto';
+import { longRunningTaskWrapper } from '../util/longRunningTaskWrapper';
+
+import type { GroupJoinInfoClass } from '../textsecure.d';
+import type { ConversationAttributesType } from '../model-types.d';
+import type { ConversationModel } from '../models/conversations';
+import type { PreJoinConversationType } from '../state/ducks/conversations';
+
+export async function joinViaLink(hash: string): Promise<void> {
+  let inviteLinkPassword: string;
+  let masterKey: string;
+  try {
+    ({ inviteLinkPassword, masterKey } = parseGroupLink(hash));
+  } catch (error) {
+    const errorString = error && error.stack ? error.stack : error;
+    window.log.error(`joinViaLink: Failed to parse group link ${errorString}`);
+    if (error && error.name === LINK_VERSION_ERROR) {
+      showErrorDialog(
+        window.i18n('GroupV2--join--unknown-link-version'),
+        window.i18n('GroupV2--join--unknown-link-version--title')
+      );
+    } else {
+      showErrorDialog(
+        window.i18n('GroupV2--join--invalid-link'),
+        window.i18n('GroupV2--join--invalid-link--title')
+      );
+    }
+    return;
+  }
+
+  const data = deriveGroupFields(base64ToArrayBuffer(masterKey));
+  const id = arrayBufferToBase64(data.id);
+  const logId = `groupv2(${id})`;
+  const secretParams = arrayBufferToBase64(data.secretParams);
+  const publicParams = arrayBufferToBase64(data.publicParams);
+
+  const existingConversation =
+    window.ConversationController.get(id) ||
+    window.ConversationController.getByDerivedGroupV2Id(id);
+  const ourConversationId = window.ConversationController.getOurConversationIdOrThrow();
+
+  if (
+    existingConversation &&
+    existingConversation.hasMember(ourConversationId)
+  ) {
+    window.log.warn(
+      `joinViaLink/${logId}: Already a member of group, opening conversation`
+    );
+    window.reduxActions.conversations.openConversationInternal(
+      existingConversation.id
+    );
+    window.window.Whisper.ToastView.show(
+      window.Whisper.AlreadyGroupMemberToast,
+      document.getElementsByClassName('conversation-stack')[0]
+    );
+    return;
+  }
+
+  let result: GroupJoinInfoClass;
+
+  try {
+    result = await longRunningTaskWrapper({
+      name: 'getPreJoinGroupInfo',
+      idForLogging: idForLogging(id),
+      // If an error happens here, we won't show a dialog. We'll rely on the catch a few
+      //   lines below.
+      suppressErrorDialog: true,
+      task: () => getPreJoinGroupInfo(inviteLinkPassword, masterKey),
+    });
+  } catch (error) {
+    const errorString = error && error.stack ? error.stack : error;
+    window.log.error(
+      `joinViaLink/${logId}: Failed to fetch group info - ${errorString}`
+    );
+
+    showErrorDialog(
+      error.code && error.code === 403
+        ? window.i18n('GroupV2--join--link-revoked')
+        : window.i18n('GroupV2--join--general-join-failure'),
+      error.code && error.code === 403
+        ? window.i18n('GroupV2--join--link-revoked--title')
+        : window.i18n('GroupV2--join--general-join-failure--title')
+    );
+    return;
+  }
+
+  const ACCESS_ENUM = window.textsecure.protobuf.AccessControl.AccessRequired;
+  if (
+    result.addFromInviteLink !== ACCESS_ENUM.ADMINISTRATOR &&
+    result.addFromInviteLink !== ACCESS_ENUM.ANY
+  ) {
+    window.log.error(
+      `joinViaLink/${logId}: addFromInviteLink value of ${result.addFromInviteLink} is invalid`
+    );
+    showErrorDialog(
+      window.i18n('GroupV2--join--link-revoked'),
+      window.i18n('GroupV2--join--link-revoked--title')
+    );
+    return;
+  }
+
+  let localAvatar:
+    | {
+        loading?: boolean;
+        path?: string;
+      }
+    | undefined = result.avatar ? { loading: true } : undefined;
+  const memberCount = result.memberCount || 1;
+  const approvalRequired =
+    result.addFromInviteLink === ACCESS_ENUM.ADMINISTRATOR;
+  const title =
+    decryptGroupTitle(result.title, secretParams) ||
+    window.i18n('unknownGroup');
+
+  if (
+    approvalRequired &&
+    existingConversation &&
+    existingConversation.isMemberAwaitingApproval(ourConversationId)
+  ) {
+    window.log.warn(
+      `joinViaLink/${logId}: Already awaiting approval, opening conversation`
+    );
+    window.reduxActions.conversations.openConversationInternal(
+      existingConversation.id
+    );
+
+    window.Whisper.ToastView.show(
+      window.Whisper.AlreadyRequestedToJoinToast,
+      document.getElementsByClassName('conversation-stack')[0]
+    );
+    return;
+  }
+
+  const getPreJoinConversation = (): PreJoinConversationType => {
+    let avatar;
+    if (!localAvatar) {
+      avatar = undefined;
+    } else if (localAvatar && localAvatar.loading) {
+      avatar = {
+        loading: true,
+      };
+    } else if (localAvatar && localAvatar.path) {
+      avatar = {
+        url: window.Signal.Migrations.getAbsoluteAttachmentPath(
+          localAvatar.path
+        ),
+      };
+    }
+
+    return {
+      approvalRequired,
+      avatar,
+      memberCount,
+      title,
+    };
+  };
+
+  // Explode a promise so we know when this whole join process is complete
+  const { promise, resolve, reject } = explodePromise();
+
+  const closeDialog = async () => {
+    try {
+      if (groupV2InfoDialog) {
+        groupV2InfoDialog.remove();
+        groupV2InfoDialog = undefined;
+      }
+
+      window.reduxActions.conversations.setPreJoinConversation(undefined);
+
+      if (localAvatar && localAvatar.path) {
+        await window.Signal.Migrations.deleteAttachmentData(localAvatar.path);
+      }
+      resolve();
+    } catch (error) {
+      reject(error);
+    }
+  };
+
+  const join = async () => {
+    try {
+      if (groupV2InfoDialog) {
+        groupV2InfoDialog.remove();
+        groupV2InfoDialog = undefined;
+      }
+
+      window.reduxActions.conversations.setPreJoinConversation(undefined);
+
+      await longRunningTaskWrapper({
+        name: 'joinViaLink',
+        idForLogging: idForLogging(id),
+        // If an error happens here, we won't show a dialog. We'll rely on a top-level
+        //   error dialog provided by the caller of this function.
+        suppressErrorDialog: true,
+        task: async () => {
+          let targetConversation =
+            existingConversation ||
+            window.ConversationController.get(id) ||
+            window.ConversationController.getByDerivedGroupV2Id(id);
+          let tempConversation: ConversationModel | undefined;
+
+          // Check again to ensure that we haven't already joined or requested to join
+          //   via some other process. If so, just open that conversation.
+          if (
+            targetConversation &&
+            (targetConversation.hasMember(ourConversationId) ||
+              (approvalRequired &&
+                targetConversation.isMemberAwaitingApproval(ourConversationId)))
+          ) {
+            window.log.warn(
+              `joinViaLink/${logId}: User is part of group on second check, opening conversation`
+            );
+            window.reduxActions.conversations.openConversationInternal(
+              targetConversation.id
+            );
+            return;
+          }
+
+          try {
+            if (!targetConversation) {
+              // Note: we save this temp conversation in the database, so we'll need to
+              //   clean it up if something goes wrong
+              tempConversation = window.ConversationController.getOrCreate(
+                id,
+                'group',
+                {
+                  // This will cause this conversation to be deleted at next startup
+                  isTemporary: true,
+
+                  groupVersion: 2,
+                  masterKey,
+                  secretParams,
+                  publicParams,
+
+                  left: true,
+                  revision: result.version,
+
+                  avatar:
+                    localAvatar && localAvatar.path && result.avatar
+                      ? {
+                          url: result.avatar,
+                          path: localAvatar.path,
+                        }
+                      : undefined,
+                  groupInviteLinkPassword: inviteLinkPassword,
+                  name: title,
+                  temporaryMemberCount: memberCount,
+                }
+              );
+              targetConversation = tempConversation;
+            } else {
+              // Ensure the group maintains the title and avatar you saw when attempting
+              //   to join it.
+              targetConversation.set({
+                avatar:
+                  localAvatar && localAvatar.path && result.avatar
+                    ? {
+                        url: result.avatar,
+                        path: localAvatar.path,
+                      }
+                    : undefined,
+                groupInviteLinkPassword: inviteLinkPassword,
+                name: title,
+                temporaryMemberCount: memberCount,
+              });
+              window.Signal.Data.updateConversation(
+                targetConversation.attributes
+              );
+            }
+
+            if (targetConversation.isGroupV1()) {
+              await targetConversation.joinGroupV2ViaLinkAndMigrate({
+                approvalRequired,
+                inviteLinkPassword,
+                revision: result.version || 0,
+              });
+            } else {
+              await targetConversation.joinGroupV2ViaLink({
+                inviteLinkPassword,
+                approvalRequired,
+              });
+            }
+
+            if (tempConversation) {
+              tempConversation.set({
+                // We want to keep this conversation around, since the join succeeded
+                isTemporary: undefined,
+              });
+              window.Signal.Data.updateConversation(
+                tempConversation.attributes
+              );
+            }
+
+            window.reduxActions.conversations.openConversationInternal(
+              targetConversation.id
+            );
+          } catch (error) {
+            // Delete newly-created conversation if we encountered any errors
+            if (tempConversation) {
+              window.ConversationController.dangerouslyRemoveById(
+                tempConversation.id
+              );
+              await window.Signal.Data.removeConversation(tempConversation.id, {
+                Conversation: window.Whisper.Conversation,
+              });
+            }
+
+            throw error;
+          }
+        },
+      });
+      resolve();
+    } catch (error) {
+      reject(error);
+    }
+  };
+
+  // Initial add to redux, with basic group information
+  window.reduxActions.conversations.setPreJoinConversation(
+    getPreJoinConversation()
+  );
+
+  window.log.info(`joinViaLink/${logId}: Showing modal`);
+
+  let groupV2InfoDialog = new Whisper.ReactWrapperView({
+    className: 'group-v2-join-dialog-wrapper',
+    JSX: window.Signal.State.Roots.createGroupV2JoinModal(window.reduxStore, {
+      join,
+      onClose: closeDialog,
+    }),
+  });
+
+  // We declare a new function here so we can await but not block
+  const fetchAvatar = async () => {
+    if (result.avatar) {
+      localAvatar = {
+        loading: true,
+      };
+
+      const attributes: Pick<
+        ConversationAttributesType,
+        'avatar' | 'secretParams'
+      > = {
+        avatar: null,
+        secretParams,
+      };
+      await applyNewAvatar(result.avatar, attributes, logId);
+
+      if (attributes.avatar && attributes.avatar.path) {
+        localAvatar = {
+          path: attributes.avatar.path,
+        };
+
+        // Dialog has been dismissed; we'll delete the unneeeded avatar
+        if (!groupV2InfoDialog) {
+          await window.Signal.Migrations.deleteAttachmentData(
+            attributes.avatar.path
+          );
+          return;
+        }
+      } else {
+        localAvatar = undefined;
+      }
+
+      // Update join dialog with newly-downloaded avatar
+      window.reduxActions.conversations.setPreJoinConversation(
+        getPreJoinConversation()
+      );
+    }
+  };
+
+  fetchAvatar();
+
+  await promise;
+}
+
+function showErrorDialog(description: string, title: string) {
+  const errorView = new window.Whisper.ReactWrapperView({
+    className: 'error-modal-wrapper',
+    Component: window.Signal.Components.ErrorModal,
+    props: {
+      title,
+      description,
+      onClose: () => {
+        errorView.remove();
+      },
+    },
+  });
+}
+
+function explodePromise(): {
+  promise: Promise<void>;
+  resolve: () => void;
+  reject: (error: Error) => void;
+} {
+  let resolve: () => void;
+  let reject: (error: Error) => void;
+
+  const promise = new Promise<void>((innerResolve, innerReject) => {
+    resolve = innerResolve;
+    reject = innerReject;
+  });
+
+  return {
+    promise,
+    // Typescript thinks that resolve and reject can be undefined here.
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    resolve: resolve!,
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    reject: reject!,
+  };
+}
diff --git a/ts/model-types.d.ts b/ts/model-types.d.ts
index 5e845c53c..d8d3394af 100644
--- a/ts/model-types.d.ts
+++ b/ts/model-types.d.ts
@@ -211,6 +211,9 @@ export type ConversationAttributesType = {
 
   // Group-only
   groupId?: string;
+  // A shorthand, representing whether the user is part of the group. Not strictly for
+  //   when the user manually left the group. But historically, that was the only way
+  //   to leave a group.
   left: boolean;
   groupVersion?: number;
 
@@ -233,7 +236,7 @@ export type ConversationAttributesType = {
   avatar?: {
     url: string;
     path: string;
-    hash: string;
+    hash?: string;
   } | null;
   expireTimer?: number;
   membersV2?: Array<GroupV2MemberType>;
@@ -242,6 +245,10 @@ export type ConversationAttributesType = {
   groupInviteLinkPassword?: string;
   previousGroupV1Id?: string;
   previousGroupV1Members?: Array<string>;
+
+  // Used only when user is waiting for approval to join via link
+  isTemporary?: boolean;
+  temporaryMemberCount?: number;
 };
 
 export type GroupV2MemberType = {
diff --git a/ts/models/conversations.ts b/ts/models/conversations.ts
index f7686d4ca..004f13bb5 100644
--- a/ts/models/conversations.ts
+++ b/ts/models/conversations.ts
@@ -331,6 +331,22 @@ export class ConversationModel extends window.Backbone.Model<
     );
   }
 
+  isMemberAwaitingApproval(conversationId: string): boolean {
+    if (!this.isGroupV2()) {
+      return false;
+    }
+    const pendingAdminApprovalV2 = this.get('pendingAdminApprovalV2');
+
+    if (!pendingAdminApprovalV2 || !pendingAdminApprovalV2.length) {
+      return false;
+    }
+
+    return window._.any(
+      pendingAdminApprovalV2,
+      item => item.conversationId === conversationId
+    );
+  }
+
   isMember(conversationId: string): boolean {
     if (!this.isGroupV2()) {
       throw new Error(
@@ -483,6 +499,97 @@ export class ConversationModel extends window.Backbone.Model<
     });
   }
 
+  async addPendingApprovalRequest(): Promise<
+    GroupChangeClass.Actions | undefined
+  > {
+    const idLog = this.idForLogging();
+
+    // Hard-coded to our own ID, because you don't add other users for admin approval
+    const conversationId = window.ConversationController.getOurConversationIdOrThrow();
+
+    const toRequest = window.ConversationController.get(conversationId);
+    if (!toRequest) {
+      throw new Error(
+        `addPendingApprovalRequest/${idLog}: No conversation found for conversation ${conversationId}`
+      );
+    }
+
+    // We need the user's profileKeyCredential, which requires a roundtrip with the
+    //   server, and most definitely their profileKey. A getProfiles() call will
+    //   ensure that we have as much as we can get with the data we have.
+    let profileKeyCredentialBase64 = toRequest.get('profileKeyCredential');
+    if (!profileKeyCredentialBase64) {
+      await toRequest.getProfiles();
+
+      profileKeyCredentialBase64 = toRequest.get('profileKeyCredential');
+      if (!profileKeyCredentialBase64) {
+        throw new Error(
+          `promotePendingMember/${idLog}: No profileKeyCredential for conversation ${toRequest.idForLogging()}`
+        );
+      }
+    }
+
+    // This user's pending state may have changed in the time between the user's
+    //   button press and when we get here. It's especially important to check here
+    //   in conflict/retry cases.
+    if (this.isMemberAwaitingApproval(conversationId)) {
+      window.log.warn(
+        `addPendingApprovalRequest/${idLog}: ${conversationId} already in pending approval.`
+      );
+      return undefined;
+    }
+
+    return window.Signal.Groups.buildAddPendingAdminApprovalMemberChange({
+      group: this.attributes,
+      profileKeyCredentialBase64,
+      serverPublicParamsBase64: window.getServerPublicParams(),
+    });
+  }
+
+  async addMember(
+    conversationId: string
+  ): Promise<GroupChangeClass.Actions | undefined> {
+    const idLog = this.idForLogging();
+
+    const toRequest = window.ConversationController.get(conversationId);
+    if (!toRequest) {
+      throw new Error(
+        `addMember/${idLog}: No conversation found for conversation ${conversationId}`
+      );
+    }
+
+    // We need the user's profileKeyCredential, which requires a roundtrip with the
+    //   server, and most definitely their profileKey. A getProfiles() call will
+    //   ensure that we have as much as we can get with the data we have.
+    let profileKeyCredentialBase64 = toRequest.get('profileKeyCredential');
+    if (!profileKeyCredentialBase64) {
+      await toRequest.getProfiles();
+
+      profileKeyCredentialBase64 = toRequest.get('profileKeyCredential');
+      if (!profileKeyCredentialBase64) {
+        throw new Error(
+          `addMember/${idLog}: No profileKeyCredential for conversation ${toRequest.idForLogging()}`
+        );
+      }
+    }
+
+    // This user's pending state may have changed in the time between the user's
+    //   button press and when we get here. It's especially important to check here
+    //   in conflict/retry cases.
+    if (this.isMember(conversationId)) {
+      window.log.warn(
+        `addMember/${idLog}: ${conversationId} already a member.`
+      );
+      return undefined;
+    }
+
+    return window.Signal.Groups.buildAddMember({
+      group: this.attributes,
+      profileKeyCredentialBase64,
+      serverPublicParamsBase64: window.getServerPublicParams(),
+    });
+  }
+
   async removePendingMember(
     conversationIds: Array<string>
   ): Promise<GroupChangeClass.Actions | undefined> {
@@ -609,142 +716,19 @@ export class ConversationModel extends window.Backbone.Model<
 
   async modifyGroupV2({
     name,
+    inviteLinkPassword,
     createGroupChange,
   }: {
     name: string;
+    inviteLinkPassword?: string;
     createGroupChange: () => Promise<GroupChangeClass.Actions | undefined>;
   }): Promise<void> {
-    const idLog = `${name}/${this.idForLogging()}`;
-
-    if (!this.isGroupV2()) {
-      throw new Error(
-        `modifyGroupV2/${idLog}: Called for non-GroupV2 conversation`
-      );
-    }
-
-    const ONE_MINUTE = 1000 * 60;
-    const startTime = Date.now();
-    const timeoutTime = startTime + ONE_MINUTE;
-
-    const MAX_ATTEMPTS = 5;
-
-    for (let attempt = 0; attempt < MAX_ATTEMPTS; attempt += 1) {
-      window.log.info(`modifyGroupV2/${idLog}: Starting attempt ${attempt}`);
-      try {
-        // eslint-disable-next-line no-await-in-loop
-        await window.waitForEmptyEventQueue();
-
-        window.log.info(`modifyGroupV2/${idLog}: Queuing attempt ${attempt}`);
-
-        // eslint-disable-next-line no-await-in-loop
-        await this.queueJob(async () => {
-          window.log.info(`modifyGroupV2/${idLog}: Running attempt ${attempt}`);
-
-          const actions = await createGroupChange();
-          if (!actions) {
-            window.log.warn(
-              `modifyGroupV2/${idLog}: No change actions. Returning early.`
-            );
-            return;
-          }
-
-          // The new revision has to be exactly one more than the current revision
-          //   or it won't upload properly, and it won't apply in maybeUpdateGroup
-          const currentRevision = this.get('revision');
-          const newRevision = actions.version;
-
-          if ((currentRevision || 0) + 1 !== newRevision) {
-            throw new Error(
-              `modifyGroupV2/${idLog}: Revision mismatch - ${currentRevision} to ${newRevision}.`
-            );
-          }
-
-          // Upload. If we don't have permission, the server will return an error here.
-          const groupChange = await window.Signal.Groups.uploadGroupChange({
-            actions,
-            group: this.attributes,
-          });
-
-          const groupChangeBuffer = groupChange.toArrayBuffer();
-          const groupChangeBase64 = arrayBufferToBase64(groupChangeBuffer);
-
-          // Apply change locally, just like we would with an incoming change. This will
-          //   change conversation state and add change notifications to the timeline.
-          await window.Signal.Groups.maybeUpdateGroup({
-            conversation: this,
-            groupChangeBase64,
-            newRevision,
-          });
-
-          // Send message to notify group members (including pending members) of change
-          const profileKey = this.get('profileSharing')
-            ? window.storage.get('profileKey')
-            : undefined;
-
-          const sendOptions = this.getSendOptions();
-          const timestamp = Date.now();
-
-          const promise = this.wrapSend(
-            window.textsecure.messaging.sendMessageToGroup(
-              {
-                groupV2: this.getGroupV2Info({
-                  groupChange: groupChangeBuffer,
-                  includePendingMembers: true,
-                }),
-                timestamp,
-                profileKey,
-              },
-              sendOptions
-            )
-          );
-
-          // We don't save this message; we just use it to ensure that a sync message is
-          //   sent to our linked devices.
-          const m = new window.Whisper.Message(({
-            conversationId: this.id,
-            type: 'not-to-save',
-            sent_at: timestamp,
-            received_at: timestamp,
-            // TODO: DESKTOP-722
-            // this type does not fully implement the interface it is expected to
-          } as unknown) as MessageAttributesType);
-
-          // This is to ensure that the functions in send() and sendSyncMessage()
-          //   don't save anything to the database.
-          m.doNotSave = true;
-
-          await m.send(promise);
-        });
-
-        // If we've gotten here with no error, we exit!
-        window.log.info(
-          `modifyGroupV2/${idLog}: Update complete, with attempt ${attempt}!`
-        );
-        break;
-      } catch (error) {
-        if (error.code === 409 && Date.now() <= timeoutTime) {
-          window.log.info(
-            `modifyGroupV2/${idLog}: Conflict while updating. Trying again...`
-          );
-
-          // eslint-disable-next-line no-await-in-loop
-          await this.fetchLatestGroupV2Data();
-        } else if (error.code === 409) {
-          window.log.error(
-            `modifyGroupV2/${idLog}: Conflict while updating. Timed out; not retrying.`
-          );
-          // We don't wait here because we're breaking out of the loop immediately.
-          this.fetchLatestGroupV2Data();
-          throw error;
-        } else {
-          const errorString = error && error.stack ? error.stack : error;
-          window.log.error(
-            `modifyGroupV2/${idLog}: Error updating: ${errorString}`
-          );
-          throw error;
-        }
-      }
-    }
+    await window.Signal.Groups.modifyGroupV2({
+      createGroupChange,
+      conversation: this,
+      inviteLinkPassword,
+      name,
+    });
   }
 
   isEverUnregistered(): boolean {
@@ -1324,6 +1308,9 @@ export class ConversationModel extends window.Backbone.Model<
       areWePending: Boolean(
         ourConversationId && this.isMemberPending(ourConversationId)
       ),
+      areWePendingApproval: Boolean(
+        ourConversationId && this.isMemberAwaitingApproval(ourConversationId)
+      ),
       areWeAdmin: this.areWeAdmin(),
       canChangeTimer: this.canChangeTimer(),
       canEditGroupInfo: this.canEditGroupInfo(),
@@ -1353,9 +1340,7 @@ export class ConversationModel extends window.Backbone.Model<
       lastUpdated: this.get('timestamp')!,
       left: Boolean(this.get('left')),
       markedUnread: this.get('markedUnread')!,
-      membersCount: this.isPrivate()
-        ? undefined
-        : (this.get('membersV2')! || this.get('members')! || []).length,
+      membersCount: this.getMembersCount(),
       memberships: this.getMemberships(),
       pendingMemberships: this.getPendingMemberships(),
       pendingApprovalMemberships: this.getPendingApprovalMemberships(),
@@ -1427,6 +1412,26 @@ export class ConversationModel extends window.Backbone.Model<
     window.Signal.Data.updateConversation(this.attributes);
   }
 
+  getMembersCount(): number {
+    if (this.isPrivate()) {
+      return 1;
+    }
+
+    const memberList = this.get('membersV2') || this.get('members');
+
+    // We'll fail over if the member list is empty
+    if (memberList && memberList.length) {
+      return memberList.length;
+    }
+
+    const temporaryMemberCount = this.get('temporaryMemberCount');
+    if (window._.isNumber(temporaryMemberCount)) {
+      return temporaryMemberCount;
+    }
+
+    return 0;
+  }
+
   decrementMessageCount(): void {
     this.set({
       messageCount: Math.max((this.get('messageCount') || 0) - 1, 0),
@@ -1623,6 +1628,98 @@ export class ConversationModel extends window.Backbone.Model<
     }
   }
 
+  async joinGroupV2ViaLinkAndMigrate({
+    approvalRequired,
+    inviteLinkPassword,
+    revision,
+  }: {
+    approvalRequired: boolean;
+    inviteLinkPassword: string;
+    revision: number;
+  }): Promise<void> {
+    await window.Signal.Groups.joinGroupV2ViaLinkAndMigrate({
+      approvalRequired,
+      conversation: this,
+      inviteLinkPassword,
+      revision,
+    });
+  }
+
+  async joinGroupV2ViaLink({
+    inviteLinkPassword,
+    approvalRequired,
+  }: {
+    inviteLinkPassword: string;
+    approvalRequired: boolean;
+  }): Promise<void> {
+    const ourConversationId = window.ConversationController.getOurConversationIdOrThrow();
+    try {
+      if (approvalRequired) {
+        await this.modifyGroupV2({
+          name: 'requestToJoin',
+          inviteLinkPassword,
+          createGroupChange: () => this.addPendingApprovalRequest(),
+        });
+      } else {
+        await this.modifyGroupV2({
+          name: 'joinGroup',
+          inviteLinkPassword,
+          createGroupChange: () => this.addMember(ourConversationId),
+        });
+      }
+    } catch (error) {
+      const ALREADY_REQUESTED_TO_JOIN =
+        '{"code":400,"message":"cannot ask to join via invite link if already asked to join"}';
+      if (!error.response) {
+        throw error;
+      } else {
+        const errorDetails = stringFromBytes(error.response);
+        if (errorDetails !== ALREADY_REQUESTED_TO_JOIN) {
+          throw error;
+        } else {
+          window.log.info(
+            'joinGroupV2ViaLink: Got 400, but server is telling us we have already requested to join. Forcing that local state'
+          );
+          this.set({
+            pendingAdminApprovalV2: [
+              {
+                conversationId: ourConversationId,
+                timestamp: Date.now(),
+              },
+            ],
+          });
+        }
+      }
+    }
+
+    const messageRequestEnum =
+      window.textsecure.protobuf.SyncMessage.MessageRequestResponse.Type;
+
+    // Ensure active_at is set, because this is an event that justifies putting the group
+    //   in the left pane.
+    this.set({
+      messageRequestResponseType: messageRequestEnum.ACCEPT,
+      active_at: this.get('active_at') || Date.now(),
+    });
+    window.Signal.Data.updateConversation(this.attributes);
+  }
+
+  async cancelJoinRequest(): Promise<void> {
+    const ourConversationId = window.ConversationController.getOurConversationIdOrThrow();
+
+    const inviteLinkPassword = this.get('groupInviteLinkPassword');
+    if (!inviteLinkPassword) {
+      throw new Error('Missing groupInviteLinkPassword!');
+    }
+
+    await this.modifyGroupV2({
+      name: 'cancelJoinRequest',
+      inviteLinkPassword,
+      createGroupChange: () =>
+        this.denyPendingApprovalRequest(ourConversationId),
+    });
+  }
+
   async leaveGroupV2(): Promise<void> {
     const ourConversationId = window.ConversationController.getOurConversationId();
 
diff --git a/ts/state/ducks/conversations.ts b/ts/state/ducks/conversations.ts
index 613be5985..bfaf68ece 100644
--- a/ts/state/ducks/conversations.ts
+++ b/ts/state/ducks/conversations.ts
@@ -61,6 +61,7 @@ export type ConversationType = {
   avatarPath?: string;
   areWeAdmin?: boolean;
   areWePending?: boolean;
+  areWePendingApproval?: boolean;
   canChangeTimer?: boolean;
   canEditGroupInfo?: boolean;
   color?: ColorType;
@@ -208,7 +209,18 @@ export type MessagesByConversationType = {
   [key: string]: ConversationMessageType | undefined;
 };
 
+export type PreJoinConversationType = {
+  avatar?: {
+    loading?: boolean;
+    url?: string;
+  };
+  memberCount: number;
+  title: string;
+  approvalRequired: boolean;
+};
+
 export type ConversationsStateType = {
+  preJoinConversation?: PreJoinConversationType;
   conversationLookup: ConversationLookupType;
   conversationsByE164: ConversationLookupType;
   conversationsByUuid: ConversationLookupType;
@@ -252,6 +264,13 @@ export const getConversationCallMode = (
 
 // Actions
 
+type SetPreJoinConversationActionType = {
+  type: 'SET_PRE_JOIN_CONVERSATION';
+  payload: {
+    data: PreJoinConversationType | undefined;
+  };
+};
+
 type ConversationAddedActionType = {
   type: 'CONVERSATION_ADDED';
   payload: {
@@ -421,34 +440,33 @@ type SetRecentMediaItemsActionType = {
 };
 
 export type ConversationActionType =
+  | ClearChangedMessagesActionType
+  | ClearSelectedMessageActionType
+  | ClearUnreadMetricsActionType
   | ConversationAddedActionType
   | ConversationChangedActionType
   | ConversationRemovedActionType
   | ConversationUnloadedActionType
-  | RemoveAllConversationsActionType
-  | MessageSelectedActionType
-  | MessageSizeChangedActionType
   | MessageChangedActionType
   | MessageDeletedActionType
   | MessagesAddedActionType
+  | MessageSelectedActionType
+  | MessageSizeChangedActionType
+  | MessagesResetActionType
+  | RemoveAllConversationsActionType
   | RepairNewestMessageActionType
   | RepairOldestMessageActionType
-  | MessagesResetActionType
-  | SetMessagesLoadingActionType
+  | ScrollToMessageActionType
+  | SelectedConversationChangedActionType
+  | SetConversationHeaderTitleActionType
   | SetIsNearBottomActionType
   | SetLoadCountdownStartActionType
-  | ClearChangedMessagesActionType
-  | ClearSelectedMessageActionType
-  | ClearUnreadMetricsActionType
-  | ScrollToMessageActionType
-  | SetConversationHeaderTitleActionType
-  | SetSelectedConversationPanelDepthActionType
-  | SelectedConversationChangedActionType
-  | MessageDeletedActionType
-  | SelectedConversationChangedActionType
+  | SetMessagesLoadingActionType
+  | SetPreJoinConversationActionType
   | SetRecentMediaItemsActionType
-  | ShowInboxActionType
-  | ShowArchivedConversationsActionType;
+  | SetSelectedConversationPanelDepthActionType
+  | ShowArchivedConversationsActionType
+  | ShowInboxActionType;
 
 // Action Creators
 
@@ -462,8 +480,8 @@ export const actions = {
   conversationUnloaded,
   messageChanged,
   messageDeleted,
-  messageSizeChanged,
   messagesAdded,
+  messageSizeChanged,
   messagesReset,
   openConversationExternal,
   openConversationInternal,
@@ -475,6 +493,7 @@ export const actions = {
   setIsNearBottom,
   setLoadCountdownStart,
   setMessagesLoading,
+  setPreJoinConversation,
   setRecentMediaItems,
   setSelectedConversationHeaderTitle,
   setSelectedConversationPanelDepth,
@@ -482,6 +501,16 @@ export const actions = {
   showInbox,
 };
 
+function setPreJoinConversation(
+  data: PreJoinConversationType | undefined
+): SetPreJoinConversationActionType {
+  return {
+    type: 'SET_PRE_JOIN_CONVERSATION',
+    payload: {
+      data,
+    },
+  };
+}
 function conversationAdded(
   id: string,
   data: ConversationType
@@ -924,6 +953,15 @@ export function reducer(
   state: Readonly<ConversationsStateType> = getEmptyState(),
   action: Readonly<ConversationActionType>
 ): ConversationsStateType {
+  if (action.type === 'SET_PRE_JOIN_CONVERSATION') {
+    const { payload } = action;
+    const { data } = payload;
+
+    return {
+      ...state,
+      preJoinConversation: data,
+    };
+  }
   if (action.type === 'CONVERSATION_ADDED') {
     const { payload } = action;
     const { id, data } = payload;
diff --git a/ts/state/roots/createGroupV2JoinModal.tsx b/ts/state/roots/createGroupV2JoinModal.tsx
new file mode 100644
index 000000000..43a64389a
--- /dev/null
+++ b/ts/state/roots/createGroupV2JoinModal.tsx
@@ -0,0 +1,25 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import React from 'react';
+import { Provider } from 'react-redux';
+
+import { Store } from 'redux';
+
+import { ModalHost } from '../../components/ModalHost';
+import { SmartGroupV2JoinDialog, PropsType } from '../smart/GroupV2JoinDialog';
+
+export const createGroupV2JoinModal = (
+  store: Store,
+  props: PropsType
+): React.ReactElement => {
+  const { onClose } = props;
+
+  return (
+    <Provider store={store}>
+      <ModalHost onClose={onClose}>
+        <SmartGroupV2JoinDialog {...props} />
+      </ModalHost>
+    </Provider>
+  );
+};
diff --git a/ts/state/selectors/conversations.ts b/ts/state/selectors/conversations.ts
index 42cec012f..3aa4606d4 100644
--- a/ts/state/selectors/conversations.ts
+++ b/ts/state/selectors/conversations.ts
@@ -14,6 +14,7 @@ import {
   MessageLookupType,
   MessagesByConversationType,
   MessageType,
+  PreJoinConversationType,
 } from '../ducks/conversations';
 import { getOwn } from '../../util/getOwn';
 import type { CallsByConversationType } from '../ducks/calling';
@@ -48,6 +49,12 @@ export const getPlaceholderContact = (): ConversationType => {
 export const getConversations = (state: StateType): ConversationsStateType =>
   state.conversations;
 
+export const getPreJoinConversation = createSelector(
+  getConversations,
+  (state: ConversationsStateType): PreJoinConversationType | undefined => {
+    return state.preJoinConversation;
+  }
+);
 export const getConversationLookup = createSelector(
   getConversations,
   (state: ConversationsStateType): ConversationLookupType => {
diff --git a/ts/state/smart/GroupV2JoinDialog.tsx b/ts/state/smart/GroupV2JoinDialog.tsx
new file mode 100644
index 000000000..1445732db
--- /dev/null
+++ b/ts/state/smart/GroupV2JoinDialog.tsx
@@ -0,0 +1,36 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { connect } from 'react-redux';
+import { mapDispatchToProps } from '../actions';
+import {
+  GroupV2JoinDialog,
+  PropsType as GroupV2JoinDialogPropsType,
+} from '../../components/GroupV2JoinDialog';
+import { StateType } from '../reducer';
+
+import { getIntl } from '../selectors/user';
+import { getPreJoinConversation } from '../selectors/conversations';
+
+export type PropsType = Pick<GroupV2JoinDialogPropsType, 'join' | 'onClose'>;
+
+const mapStateToProps = (
+  state: StateType,
+  props: PropsType
+): GroupV2JoinDialogPropsType => {
+  const preJoinConversation = getPreJoinConversation(state);
+
+  if (!preJoinConversation) {
+    throw new Error('smart/GroupV2JoinDialog: No pre-join conversation!');
+  }
+
+  return {
+    ...props,
+    ...preJoinConversation,
+    i18n: getIntl(state),
+  };
+};
+
+const smart = connect(mapStateToProps, mapDispatchToProps);
+
+export const SmartGroupV2JoinDialog = smart(GroupV2JoinDialog);
diff --git a/ts/test-both/util/webSafeBase64_test.ts b/ts/test-both/util/webSafeBase64_test.ts
new file mode 100644
index 000000000..7e0fe2f5d
--- /dev/null
+++ b/ts/test-both/util/webSafeBase64_test.ts
@@ -0,0 +1,85 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+
+import { toWebSafeBase64, fromWebSafeBase64 } from '../../util/webSafeBase64';
+
+describe('both/util/webSafeBase64', () => {
+  it('roundtrips with all elements', () => {
+    const base64 = 'X0KjoAj3h7Tu9YjJ++PamFc4kAg//D4FKommANpP41I=';
+
+    const webSafe = toWebSafeBase64(base64);
+    const actual = fromWebSafeBase64(webSafe);
+
+    assert.strictEqual(base64, actual);
+  });
+
+  describe('#toWebSafeBase64', () => {
+    it('replaces +', () => {
+      const base64 = 'X++y';
+      const expected = 'X--y';
+      const actual = toWebSafeBase64(base64);
+
+      assert.strictEqual(expected, actual);
+    });
+
+    it('replaces /', () => {
+      const base64 = 'X//y';
+      const expected = 'X__y';
+      const actual = toWebSafeBase64(base64);
+
+      assert.strictEqual(expected, actual);
+    });
+
+    it('removes =', () => {
+      const base64 = 'X===';
+      const expected = 'X';
+      const actual = toWebSafeBase64(base64);
+
+      assert.strictEqual(expected, actual);
+    });
+  });
+
+  describe('#fromWebSafeBase64', () => {
+    it('replaces -', () => {
+      const webSafeBase64 = 'X--y';
+      const expected = 'X++y';
+      const actual = fromWebSafeBase64(webSafeBase64);
+
+      assert.strictEqual(expected, actual);
+    });
+
+    it('replaces _', () => {
+      const webSafeBase64 = 'X__y';
+      const expected = 'X//y';
+      const actual = fromWebSafeBase64(webSafeBase64);
+
+      assert.strictEqual(expected, actual);
+    });
+
+    it('adds ===', () => {
+      const webSafeBase64 = 'X';
+      const expected = 'X===';
+      const actual = fromWebSafeBase64(webSafeBase64);
+
+      assert.strictEqual(expected, actual);
+    });
+
+    it('adds ==', () => {
+      const webSafeBase64 = 'Xy';
+      const expected = 'Xy==';
+      const actual = fromWebSafeBase64(webSafeBase64);
+
+      assert.strictEqual(expected, actual);
+    });
+
+    it('adds =', () => {
+      const webSafeBase64 = 'XyZ';
+      const expected = 'XyZ=';
+      const actual = fromWebSafeBase64(webSafeBase64);
+
+      assert.strictEqual(expected, actual);
+    });
+  });
+});
diff --git a/ts/test-electron/state/ducks/conversations_test.ts b/ts/test-electron/state/ducks/conversations_test.ts
index 9f01edea0..871c62a2f 100644
--- a/ts/test-electron/state/ducks/conversations_test.ts
+++ b/ts/test-electron/state/ducks/conversations_test.ts
@@ -20,6 +20,7 @@ const {
   messageSizeChanged,
   repairNewestMessage,
   repairOldestMessage,
+  setPreJoinConversation,
 } = actions;
 
 describe('both/state/ducks/conversations', () => {
@@ -577,5 +578,39 @@ describe('both/state/ducks/conversations', () => {
         assert.equal(actual, state);
       });
     });
+
+    describe('SET_PRE_JOIN_CONVERSATION', () => {
+      const startState = {
+        ...getEmptyState(),
+      };
+
+      it('starts with empty value', () => {
+        assert.isUndefined(startState.preJoinConversation);
+      });
+
+      it('sets value as provided', () => {
+        const preJoinConversation = {
+          title: 'Pre-join group!',
+          memberCount: 4,
+          approvalRequired: false,
+        };
+        const stateWithData = reducer(
+          startState,
+          setPreJoinConversation(preJoinConversation)
+        );
+
+        assert.deepEqual(
+          stateWithData.preJoinConversation,
+          preJoinConversation
+        );
+
+        const resetState = reducer(
+          stateWithData,
+          setPreJoinConversation(undefined)
+        );
+
+        assert.isUndefined(resetState.preJoinConversation);
+      });
+    });
   });
 });
diff --git a/ts/test-node/util/sgnlHref_test.ts b/ts/test-node/util/sgnlHref_test.ts
index 85c4e16d2..b09c9ff78 100644
--- a/ts/test-node/util/sgnlHref_test.ts
+++ b/ts/test-node/util/sgnlHref_test.ts
@@ -100,11 +100,12 @@ describe('sgnlHref', () => {
         'sgnl://foo?',
         'SGNL://foo?',
         'sgnl://user:pass@foo',
-        'sgnl://foo/path/data#hash-data',
+        'sgnl://foo/path/data',
       ].forEach(href => {
         assert.deepEqual(parseSgnlHref(href, explodingLogger), {
           command: 'foo',
           args: new Map<string, string>(),
+          hash: undefined,
         });
       });
     });
@@ -124,6 +125,7 @@ describe('sgnlHref', () => {
             ['empty', ''],
             ['encoded', 'hello world'],
           ]),
+          hash: undefined,
         }
       );
     });
@@ -144,17 +146,30 @@ describe('sgnlHref', () => {
       );
     });
 
+    it('includes hash', () => {
+      [
+        'sgnl://foo?bar=baz#somehash',
+        'sgnl://user:pass@foo?bar=baz#somehash',
+      ].forEach(href => {
+        assert.deepEqual(parseSgnlHref(href, explodingLogger), {
+          command: 'foo',
+          args: new Map([['bar', 'baz']]),
+          hash: 'somehash',
+        });
+      });
+    });
+
     it('ignores other parts of the URL', () => {
       [
         'sgnl://foo?bar=baz',
         'sgnl://foo/?bar=baz',
         'sgnl://foo/lots/of/path?bar=baz',
-        'sgnl://foo?bar=baz#hash',
         'sgnl://user:pass@foo?bar=baz',
       ].forEach(href => {
         assert.deepEqual(parseSgnlHref(href, explodingLogger), {
           command: 'foo',
           args: new Map([['bar', 'baz']]),
+          hash: undefined,
         });
       });
     });
diff --git a/ts/textsecure.d.ts b/ts/textsecure.d.ts
index 3e9a6de7a..4543432b5 100644
--- a/ts/textsecure.d.ts
+++ b/ts/textsecure.d.ts
@@ -176,6 +176,7 @@ type GroupsProtobufTypes = {
   GroupAttributeBlob: typeof GroupAttributeBlobClass;
   GroupExternalCredential: typeof GroupExternalCredentialClass;
   GroupInviteLink: typeof GroupInviteLinkClass;
+  GroupJoinInfo: typeof GroupJoinInfoClass;
 };
 
 type SignalServiceProtobufTypes = {
@@ -494,6 +495,22 @@ export declare namespace GroupChangesClass {
   }
 }
 
+export declare class GroupAttributeBlobClass {
+  static decode: (
+    data: ArrayBuffer | ByteBufferClass,
+    encoding?: string
+  ) => GroupAttributeBlobClass;
+  toArrayBuffer(): ArrayBuffer;
+
+  title?: string;
+  avatar?: ProtoBinaryType;
+  disappearingMessagesDuration?: number;
+
+  // Note: this isn't part of the proto, but our protobuf library tells us which
+  //   field has been set with this prop.
+  content: 'title' | 'avatar' | 'disappearingMessagesDuration';
+}
+
 export declare class GroupExternalCredentialClass {
   static decode: (
     data: ArrayBuffer | ByteBufferClass,
@@ -524,20 +541,19 @@ export declare namespace GroupInviteLinkClass {
   }
 }
 
-export declare class GroupAttributeBlobClass {
+export declare class GroupJoinInfoClass {
   static decode: (
     data: ArrayBuffer | ByteBufferClass,
     encoding?: string
-  ) => GroupAttributeBlobClass;
-  toArrayBuffer(): ArrayBuffer;
+  ) => GroupJoinInfoClass;
 
-  title?: string;
-  avatar?: ProtoBinaryType;
-  disappearingMessagesDuration?: number;
-
-  // Note: this isn't part of the proto, but our protobuf library tells us which
-  //   field has been set with this prop.
-  content: 'title' | 'avatar' | 'disappearingMessagesDuration';
+  publicKey?: ProtoBinaryType;
+  title?: ProtoBinaryType;
+  avatar?: string;
+  memberCount?: number;
+  addFromInviteLink?: AccessControlClass.AccessRequired;
+  version?: number;
+  pendingAdminApproval?: boolean;
 }
 
 // Previous protos
diff --git a/ts/textsecure/OutgoingMessage.ts b/ts/textsecure/OutgoingMessage.ts
index 13c5ab60f..11f9813bc 100644
--- a/ts/textsecure/OutgoingMessage.ts
+++ b/ts/textsecure/OutgoingMessage.ts
@@ -476,7 +476,7 @@ export default class OutgoingMessage {
           if (error.code === 409) {
             p = this.removeDeviceIdsForIdentifier(
               identifier,
-              error.response.extraDevices
+              error.response.extraDevices || []
             );
           } else {
             p = Promise.all(
diff --git a/ts/textsecure/SendMessage.ts b/ts/textsecure/SendMessage.ts
index 4feb7bad3..cb276ff45 100644
--- a/ts/textsecure/SendMessage.ts
+++ b/ts/textsecure/SendMessage.ts
@@ -35,6 +35,7 @@ import {
   GroupChangeClass,
   GroupClass,
   GroupExternalCredentialClass,
+  GroupJoinInfoClass,
   StorageServiceCallOptionsType,
   StorageServiceCredentials,
   SyncMessageClass,
@@ -1769,6 +1770,13 @@ export default class MessageSender {
     return this.server.getGroup(options);
   }
 
+  async getGroupFromLink(
+    groupInviteLink: string,
+    auth: GroupCredentialsType
+  ): Promise<GroupJoinInfoClass> {
+    return this.server.getGroupFromLink(groupInviteLink, auth);
+  }
+
   async getGroupLog(
     startVersion: number,
     options: GroupCredentialsType
@@ -1782,9 +1790,10 @@ export default class MessageSender {
 
   async modifyGroup(
     changes: GroupChangeClass.Actions,
-    options: GroupCredentialsType
+    options: GroupCredentialsType,
+    inviteLinkBase64?: string
   ): Promise<GroupChangeClass> {
-    return this.server.modifyGroup(changes, options);
+    return this.server.modifyGroup(changes, options, inviteLinkBase64);
   }
 
   async leaveGroup(
diff --git a/ts/textsecure/WebAPI.ts b/ts/textsecure/WebAPI.ts
index 72497a578..82ab00297 100644
--- a/ts/textsecure/WebAPI.ts
+++ b/ts/textsecure/WebAPI.ts
@@ -29,6 +29,7 @@ import { v4 as getGuid } from 'uuid';
 
 import { Long } from '../window.d';
 import { getUserAgent } from '../util/getUserAgent';
+import { toWebSafeBase64 } from '../util/webSafeBase64';
 import { isPackIdValid, redactPackId } from '../../js/modules/stickers';
 import {
   arrayBufferToBase64,
@@ -50,6 +51,7 @@ import {
   GroupChangeClass,
   GroupChangesClass,
   GroupClass,
+  GroupJoinInfoClass,
   GroupExternalCredentialClass,
   StorageServiceCallOptionsType,
   StorageServiceCredentials,
@@ -58,6 +60,11 @@ import {
 import { WebSocket } from './WebSocket';
 import MessageSender from './SendMessage';
 
+// Note: this will break some code that expects to be able to use err.response when a
+//   web request fails, because it will force it to text. But it is very useful for
+//   debugging failed requests.
+const DEBUG = false;
+
 type SgxConstantsType = {
   SGX_FLAGS_INITTED: Long;
   SGX_FLAGS_DEBUG: Long;
@@ -340,6 +347,10 @@ type ArrayBufferWithDetailsType = {
   response: Response;
 };
 
+function isSuccess(status: number): boolean {
+  return status >= 0 && status < 400;
+}
+
 async function _promiseAjax(
   providedUrl: string | null,
   options: PromiseAjaxOptionsType
@@ -432,7 +443,9 @@ async function _promiseAjax(
         }
 
         let resultPromise;
-        if (
+        if (DEBUG && !isSuccess(response.status)) {
+          resultPromise = response.text();
+        } else if (
           (options.responseType === 'json' ||
             options.responseType === 'jsonwithdetails') &&
           response.headers.get('Content-Type') === 'application/json'
@@ -448,45 +461,51 @@ async function _promiseAjax(
         }
 
         return resultPromise.then(result => {
-          if (
-            options.responseType === 'arraybuffer' ||
-            options.responseType === 'arraybufferwithdetails'
-          ) {
-            result = result.buffer.slice(
-              result.byteOffset,
-              result.byteOffset + result.byteLength
-            );
-          }
-          if (
-            options.responseType === 'json' ||
-            options.responseType === 'jsonwithdetails'
-          ) {
-            if (options.validateResponse) {
-              if (!_validateResponse(result, options.validateResponse)) {
-                if (options.redactUrl) {
-                  window.log.info(
-                    options.type,
-                    options.redactUrl(url),
-                    response.status,
-                    'Error'
+          if (isSuccess(response.status)) {
+            if (
+              options.responseType === 'arraybuffer' ||
+              options.responseType === 'arraybufferwithdetails'
+            ) {
+              result = result.buffer.slice(
+                result.byteOffset,
+                result.byteOffset + result.byteLength
+              );
+            }
+            if (
+              options.responseType === 'json' ||
+              options.responseType === 'jsonwithdetails'
+            ) {
+              if (options.validateResponse) {
+                if (!_validateResponse(result, options.validateResponse)) {
+                  if (options.redactUrl) {
+                    window.log.info(
+                      options.type,
+                      options.redactUrl(url),
+                      response.status,
+                      'Error'
+                    );
+                  } else {
+                    window.log.error(
+                      options.type,
+                      url,
+                      response.status,
+                      'Error'
+                    );
+                  }
+                  reject(
+                    makeHTTPError(
+                      'promiseAjax: invalid response',
+                      response.status,
+                      result,
+                      options.stack
+                    )
                   );
-                } else {
-                  window.log.error(options.type, url, response.status, 'Error');
-                }
-                reject(
-                  makeHTTPError(
-                    'promiseAjax: invalid response',
-                    response.status,
-                    result,
-                    options.stack
-                  )
-                );
 
-                return;
+                  return;
+                }
               }
             }
-          }
-          if (response.status >= 0 && response.status < 400) {
+
             if (options.redactUrl) {
               window.log.info(
                 options.type,
@@ -605,6 +624,10 @@ function makeHTTPError(
   const e = new Error(`${message}; code: ${code}`);
   e.name = 'HTTPError';
   e.code = code;
+  if (DEBUG && response) {
+    e.stack += `\nresponse: ${response}`;
+  }
+
   e.stack += `\nOriginal stack:\n${stack}`;
   if (response) {
     e.response = response;
@@ -628,6 +651,7 @@ const URL_CALLS = {
   getStickerPackUpload: 'v1/sticker/pack/form',
   groupLog: 'v1/groups/logs',
   groups: 'v1/groups',
+  groupsViaLink: 'v1/groups/join',
   groupToken: 'v1/groups/token',
   keys: 'v2/keys',
   messages: 'v1/messages',
@@ -734,6 +758,10 @@ export type WebAPIType = {
   getAvatar: (path: string) => Promise<any>;
   getDevices: () => Promise<any>;
   getGroup: (options: GroupCredentialsType) => Promise<GroupClass>;
+  getGroupFromLink: (
+    inviteLinkPassword: string,
+    auth: GroupCredentialsType
+  ) => Promise<GroupJoinInfoClass>;
   getGroupAvatar: (key: string) => Promise<ArrayBuffer>;
   getGroupCredentials: (
     startDay: number,
@@ -803,7 +831,8 @@ export type WebAPIType = {
   ) => Promise<ArrayBufferWithDetailsType>;
   modifyGroup: (
     changes: GroupChangeClass.Actions,
-    options: GroupCredentialsType
+    options: GroupCredentialsType,
+    inviteLinkBase64?: string
   ) => Promise<GroupChangeClass>;
   modifyStorageRecords: MessageSender['modifyStorageRecords'];
   putAttachment: (encryptedBin: ArrayBuffer) => Promise<any>;
@@ -955,6 +984,8 @@ export function initialize({
     return {
       confirmCode,
       createGroup,
+      fetchLinkPreviewImage,
+      fetchLinkPreviewMetadata,
       getAttachment,
       getAvatar,
       getConfig,
@@ -963,6 +994,7 @@ export function initialize({
       getGroupAvatar,
       getGroupCredentials,
       getGroupExternalCredential,
+      getGroupFromLink,
       getGroupLog,
       getIceServers,
       getKeysForIdentifier,
@@ -979,8 +1011,6 @@ export function initialize({
       getStorageManifest,
       getStorageRecords,
       getUuidsForE164s,
-      fetchLinkPreviewMetadata,
-      fetchLinkPreviewImage,
       makeProxiedRequest,
       makeSfuRequest,
       modifyGroup,
@@ -2052,9 +2082,32 @@ export function initialize({
       return window.textsecure.protobuf.Group.decode(response);
     }
 
+    async function getGroupFromLink(
+      inviteLinkPassword: string,
+      auth: GroupCredentialsType
+    ): Promise<GroupJoinInfoClass> {
+      const basicAuth = generateGroupAuth(
+        auth.groupPublicParamsHex,
+        auth.authCredentialPresentationHex
+      );
+
+      const response: ArrayBuffer = await _ajax({
+        basicAuth,
+        call: 'groupsViaLink',
+        contentType: 'application/x-protobuf',
+        host: storageUrl,
+        httpType: 'GET',
+        responseType: 'arraybuffer',
+        urlParameters: `/${toWebSafeBase64(inviteLinkPassword)}`,
+      });
+
+      return window.textsecure.protobuf.GroupJoinInfo.decode(response);
+    }
+
     async function modifyGroup(
       changes: GroupChangeClass.Actions,
-      options: GroupCredentialsType
+      options: GroupCredentialsType,
+      inviteLinkBase64?: string
     ): Promise<GroupChangeClass> {
       const basicAuth = generateGroupAuth(
         options.groupPublicParamsHex,
@@ -2070,6 +2123,9 @@ export function initialize({
         host: storageUrl,
         httpType: 'PATCH',
         responseType: 'arraybuffer',
+        urlParameters: inviteLinkBase64
+          ? `?inviteLinkPassword=${toWebSafeBase64(inviteLinkBase64)}`
+          : undefined,
       });
 
       return window.textsecure.protobuf.GroupChange.decode(response);
diff --git a/ts/util/index.ts b/ts/util/index.ts
index 90ccb1399..380327b74 100644
--- a/ts/util/index.ts
+++ b/ts/util/index.ts
@@ -22,6 +22,8 @@ import { makeLookup } from './makeLookup';
 import { missingCaseError } from './missingCaseError';
 import { parseRemoteClientExpiration } from './parseRemoteClientExpiration';
 import { sleep } from './sleep';
+import { longRunningTaskWrapper } from './longRunningTaskWrapper';
+import { toWebSafeBase64, fromWebSafeBase64 } from './webSafeBase64';
 import * as zkgroup from './zkgroup';
 
 export {
@@ -31,6 +33,7 @@ export {
   createWaitBatcher,
   deleteForEveryone,
   downloadAttachment,
+  fromWebSafeBase64,
   generateSecurityNumber,
   getSafetyNumberPlaceholder,
   getStringForProfileChange,
@@ -39,10 +42,12 @@ export {
   GoogleChrome,
   hasExpired,
   isFileDangerous,
+  longRunningTaskWrapper,
   makeLookup,
   missingCaseError,
   parseRemoteClientExpiration,
   Registration,
   sleep,
+  toWebSafeBase64,
   zkgroup,
 };
diff --git a/ts/util/lint/exceptions.json b/ts/util/lint/exceptions.json
index a8cf5154e..0b1f99219 100644
--- a/ts/util/lint/exceptions.json
+++ b/ts/util/lint/exceptions.json
@@ -14478,7 +14478,7 @@
     "rule": "DOM-innerHTML",
     "path": "ts/components/CompositionArea.js",
     "line": "    el.innerHTML = '';",
-    "lineNumber": 41,
+    "lineNumber": 42,
     "reasonCategory": "usageTrusted",
     "updated": "2020-05-20T20:10:43.540Z",
     "reasonDetail": "Our code, no user input, only clearing out the dom"
@@ -14487,7 +14487,7 @@
     "rule": "React-useRef",
     "path": "ts/components/CompositionArea.js",
     "line": "    const inputApiRef = React.useRef();",
-    "lineNumber": 59,
+    "lineNumber": 62,
     "reasonCategory": "falseMatch",
     "updated": "2020-10-26T19:12:24.410Z",
     "reasonDetail": "Doesn't refer to a DOM element."
@@ -14496,7 +14496,7 @@
     "rule": "React-useRef",
     "path": "ts/components/CompositionArea.js",
     "line": "    const attSlotRef = React.useRef(null);",
-    "lineNumber": 82,
+    "lineNumber": 85,
     "reasonCategory": "usageTrusted",
     "updated": "2020-10-26T19:12:24.410Z",
     "reasonDetail": "Needed for the composition area."
@@ -14505,7 +14505,7 @@
     "rule": "React-useRef",
     "path": "ts/components/CompositionArea.js",
     "line": "    const micCellRef = React.useRef(null);",
-    "lineNumber": 116,
+    "lineNumber": 119,
     "reasonCategory": "usageTrusted",
     "updated": "2020-10-26T19:12:24.410Z",
     "reasonDetail": "Needed for the composition area."
@@ -14514,7 +14514,7 @@
     "rule": "DOM-innerHTML",
     "path": "ts/components/CompositionArea.tsx",
     "line": "  el.innerHTML = '';",
-    "lineNumber": 92,
+    "lineNumber": 98,
     "reasonCategory": "usageTrusted",
     "updated": "2020-06-03T19:23:21.195Z",
     "reasonDetail": "Our code, no user input, only clearing out the dom"
@@ -15279,7 +15279,7 @@
     "rule": "jQuery-wrap(",
     "path": "ts/textsecure/WebAPI.js",
     "line": "            const byteBuffer = window.dcodeIO.ByteBuffer.wrap(quote, 'binary', window.dcodeIO.ByteBuffer.LITTLE_ENDIAN);",
-    "lineNumber": 1270,
+    "lineNumber": 1302,
     "reasonCategory": "falseMatch",
     "updated": "2020-09-08T23:07:22.682Z"
   },
@@ -15287,7 +15287,7 @@
     "rule": "jQuery-wrap(",
     "path": "ts/textsecure/WebAPI.ts",
     "line": "      const byteBuffer = window.dcodeIO.ByteBuffer.wrap(",
-    "lineNumber": 2174,
+    "lineNumber": 2230,
     "reasonCategory": "falseMatch",
     "updated": "2020-09-08T23:07:22.682Z"
   },
diff --git a/ts/util/longRunningTaskWrapper.ts b/ts/util/longRunningTaskWrapper.ts
new file mode 100644
index 000000000..88d916174
--- /dev/null
+++ b/ts/util/longRunningTaskWrapper.ts
@@ -0,0 +1,90 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+export async function longRunningTaskWrapper<T>({
+  name,
+  idForLogging,
+  task,
+  suppressErrorDialog,
+}: {
+  name: string;
+  idForLogging: string;
+  task: () => Promise<T>;
+  suppressErrorDialog?: boolean;
+}): Promise<T> {
+  const idLog = `${name}/${idForLogging}`;
+  const ONE_SECOND = 1000;
+  const TWO_SECONDS = 2000;
+
+  let progressView: typeof Whisper.ReactWrapperView | undefined;
+  let spinnerStart;
+  let progressTimeout: NodeJS.Timeout | undefined = setTimeout(() => {
+    window.log.info(`longRunningTaskWrapper/${idLog}: Creating spinner`);
+
+    // Note: this component uses a portal to render itself into the top-level DOM. No
+    //   need to attach it to the DOM here.
+    progressView = new Whisper.ReactWrapperView({
+      className: 'progress-modal-wrapper',
+      Component: window.Signal.Components.ProgressModal,
+    });
+    spinnerStart = Date.now();
+  }, TWO_SECONDS);
+
+  // Note: any task we put here needs to have its own safety valve; this function will
+  //   show a spinner until it's done
+  try {
+    window.log.info(`longRunningTaskWrapper/${idLog}: Starting task`);
+    const result = await task();
+    window.log.info(
+      `longRunningTaskWrapper/${idLog}: Task completed successfully`
+    );
+
+    if (progressTimeout) {
+      clearTimeout(progressTimeout);
+      progressTimeout = undefined;
+    }
+    if (progressView) {
+      const now = Date.now();
+      if (spinnerStart && now - spinnerStart < ONE_SECOND) {
+        window.log.info(
+          `longRunningTaskWrapper/${idLog}: Spinner shown for less than second, showing for another second`
+        );
+        await window.Signal.Util.sleep(ONE_SECOND);
+      }
+      progressView.remove();
+      progressView = undefined;
+    }
+
+    return result;
+  } catch (error) {
+    window.log.error(
+      `longRunningTaskWrapper/${idLog}: Error!`,
+      error && error.stack ? error.stack : error
+    );
+
+    if (progressTimeout) {
+      clearTimeout(progressTimeout);
+      progressTimeout = undefined;
+    }
+    if (progressView) {
+      progressView.remove();
+      progressView = undefined;
+    }
+
+    if (!suppressErrorDialog) {
+      window.log.info(`longRunningTaskWrapper/${idLog}: Showing error dialog`);
+
+      // Note: this component uses a portal to render itself into the top-level DOM. No
+      //   need to attach it to the DOM here.
+      const errorView = new Whisper.ReactWrapperView({
+        className: 'error-modal-wrapper',
+        Component: window.Signal.Components.ErrorModal,
+        props: {
+          onClose: () => errorView.remove(),
+        },
+      });
+    }
+
+    throw error;
+  }
+}
diff --git a/ts/util/sgnlHref.ts b/ts/util/sgnlHref.ts
index ff5ba25ad..0ae037daf 100644
--- a/ts/util/sgnlHref.ts
+++ b/ts/util/sgnlHref.ts
@@ -25,7 +25,7 @@ export function isSgnlHref(value: string | URL, logger: LoggerType): boolean {
 
 type ParsedSgnlHref =
   | { command: null; args: Map<never, never> }
-  | { command: string; args: Map<string, string> };
+  | { command: string; args: Map<string, string>; hash: string | undefined };
 export function parseSgnlHref(
   href: string,
   logger: LoggerType
@@ -42,5 +42,9 @@ export function parseSgnlHref(
     }
   });
 
-  return { command: url.host, args };
+  return {
+    command: url.host,
+    args,
+    hash: url.hash ? url.hash.slice(1) : undefined,
+  };
 }
diff --git a/ts/util/webSafeBase64.ts b/ts/util/webSafeBase64.ts
new file mode 100644
index 000000000..01dffc3e8
--- /dev/null
+++ b/ts/util/webSafeBase64.ts
@@ -0,0 +1,25 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+export function toWebSafeBase64(base64: string): string {
+  return base64.replace(/\//g, '_').replace(/\+/g, '-').replace(/=/g, '');
+}
+
+export function fromWebSafeBase64(webSafeBase64: string): string {
+  const base64 = webSafeBase64.replace(/_/g, '/').replace(/-/g, '+');
+
+  // Ensure that the character count is a multiple of four, filling in the extra
+  //   space needed with '='
+  const remainder = base64.length % 4;
+  if (remainder === 3) {
+    return `${base64}=`;
+  }
+  if (remainder === 2) {
+    return `${base64}==`;
+  }
+  if (remainder === 1) {
+    return `${base64}===`;
+  }
+
+  return base64;
+}
diff --git a/ts/views/conversation_view.ts b/ts/views/conversation_view.ts
index 545d67f17..7f6b4c5b8 100644
--- a/ts/views/conversation_view.ts
+++ b/ts/views/conversation_view.ts
@@ -280,6 +280,14 @@ Whisper.MaxAttachmentsToast = Whisper.ToastView.extend({
   template: window.i18n('maximumAttachments'),
 });
 
+Whisper.AlreadyGroupMemberToast = Whisper.ToastView.extend({
+  template: window.i18n('GroupV2--join--already-in-group'),
+});
+
+Whisper.AlreadyRequestedToJoinToast = Whisper.ToastView.extend({
+  template: window.i18n('GroupV2--join--already-awaiting-approval'),
+});
+
 Whisper.ConversationLoadingScreen = Whisper.View.extend({
   templateName: 'conversation-loading-screen',
   className: 'conversation-loading-screen',
@@ -660,6 +668,21 @@ Whisper.ConversationView = Whisper.View.extend({
         });
       },
       onStartGroupMigration: () => this.startMigrationToGV2(),
+      onCancelJoinRequest: async () => {
+        await window.showConfirmationDialog({
+          message: window.i18n(
+            'GroupV2--join--cancel-request-to-join--confirmation'
+          ),
+          okText: window.i18n('GroupV2--join--cancel-request-to-join--yes'),
+          cancelText: window.i18n('GroupV2--join--cancel-request-to-join--no'),
+          resolve: () => {
+            this.longRunningTaskWrapper({
+              name: 'onCancelJoinRequest',
+              task: async () => this.model.cancelJoinRequest(),
+            });
+          },
+        });
+      },
     };
 
     this.compositionAreaView = new Whisper.ReactWrapperView({
@@ -681,79 +704,12 @@ Whisper.ConversationView = Whisper.View.extend({
     name: string;
     task: () => Promise<T>;
   }): Promise<T> {
-    const idLog = `${name}/${this.model.idForLogging()}`;
-    const ONE_SECOND = 1000;
-    const TWO_SECONDS = 2000;
-
-    let progressView: any | undefined;
-    let spinnerStart;
-    let progressTimeout: NodeJS.Timeout | undefined = setTimeout(() => {
-      window.log.info(`longRunningTaskWrapper/${idLog}: Creating spinner`);
-
-      // Note: this component uses a portal to render itself into the top-level DOM. No
-      //   need to attach it to the DOM here.
-      progressView = new Whisper.ReactWrapperView({
-        className: 'progress-modal-wrapper',
-        Component: window.Signal.Components.ProgressModal,
-      });
-      spinnerStart = Date.now();
-    }, TWO_SECONDS);
-
-    // Note: any task we put here needs to have its own safety valve; this function will
-    //   show a spinner until it's done
-    try {
-      window.log.info(`longRunningTaskWrapper/${idLog}: Starting task`);
-      const result = await task();
-      window.log.info(
-        `longRunningTaskWrapper/${idLog}: Task completed successfully`
-      );
-
-      if (progressTimeout) {
-        clearTimeout(progressTimeout);
-        progressTimeout = undefined;
-      }
-      if (progressView) {
-        const now = Date.now();
-        if (spinnerStart && now - spinnerStart < ONE_SECOND) {
-          window.log.info(
-            `longRunningTaskWrapper/${idLog}: Spinner shown for less than second, showing for another second`
-          );
-          await window.Signal.Util.sleep(ONE_SECOND);
-        }
-        progressView.remove();
-        progressView = undefined;
-      }
-
-      return result;
-    } catch (error) {
-      window.log.error(
-        `longRunningTaskWrapper/${idLog}: Error!`,
-        error && error.stack ? error.stack : error
-      );
-
-      if (progressTimeout) {
-        clearTimeout(progressTimeout);
-        progressTimeout = undefined;
-      }
-      if (progressView) {
-        progressView.remove();
-        progressView = undefined;
-      }
-
-      window.log.info(`longRunningTaskWrapper/${idLog}: Showing error dialog`);
-
-      // Note: this component uses a portal to render itself into the top-level DOM. No
-      //   need to attach it to the DOM here.
-      const errorView = new Whisper.ReactWrapperView({
-        className: 'error-modal-wrapper',
-        Component: window.Signal.Components.ErrorModal,
-        props: {
-          onClose: () => errorView.remove(),
-        },
-      });
-
-      throw error;
-    }
+    const idForLogging = this.model.idForLogging();
+    return window.Signal.Util.longRunningTaskWrapper({
+      name,
+      idForLogging,
+      task,
+    });
   },
 
   setupTimeline() {
diff --git a/ts/window.d.ts b/ts/window.d.ts
index 8b76a0e21..ab8ff4b38 100644
--- a/ts/window.d.ts
+++ b/ts/window.d.ts
@@ -47,6 +47,7 @@ import { createConversationDetails } from './state/roots/createConversationDetai
 import { createConversationHeader } from './state/roots/createConversationHeader';
 import { createGroupLinkManagement } from './state/roots/createGroupLinkManagement';
 import { createGroupV1MigrationModal } from './state/roots/createGroupV1MigrationModal';
+import { createGroupV2JoinModal } from './state/roots/createGroupV2JoinModal';
 import { createGroupV2Permissions } from './state/roots/createGroupV2Permissions';
 import { createLeftPane } from './state/roots/createLeftPane';
 import { createPendingInvites } from './state/roots/createPendingInvites';
@@ -458,6 +459,7 @@ declare global {
           createConversationHeader: typeof createConversationHeader;
           createGroupLinkManagement: typeof createGroupLinkManagement;
           createGroupV1MigrationModal: typeof createGroupV1MigrationModal;
+          createGroupV2JoinModal: typeof createGroupV2JoinModal;
           createGroupV2Permissions: typeof createGroupV2Permissions;
           createLeftPane: typeof createLeftPane;
           createPendingInvites: typeof createPendingInvites;
@@ -510,7 +512,10 @@ declare global {
     readyForUpdates: () => void;
     logAppLoadedEvent: () => void;
 
-    // Flags
+    // Runtime Flags
+    isShowingModal?: boolean;
+
+    // Feature Flags
     isGroupCallingEnabled: () => boolean;
     GV2_ENABLE_SINGLE_CHANGE_PROCESSING: boolean;
     GV2_ENABLE_CHANGE_PROCESSING: boolean;
@@ -640,7 +645,7 @@ export type WhisperType = {
   ReactWrapperView: WhatIsThis;
   activeConfirmationView: WhatIsThis;
   ToastView: typeof Whisper.View & {
-    show: (view: Backbone.View, el: Element) => void;
+    show: (view: typeof Backbone.View, el: Element) => void;
   };
   ConversationArchivedToast: WhatIsThis;
   ConversationUnarchivedToast: WhatIsThis;
@@ -715,6 +720,8 @@ export type WhisperType = {
   deliveryReceiptBatcher: BatcherType<WhatIsThis>;
   RotateSignedPreKeyListener: WhatIsThis;
 
+  AlreadyGroupMemberToast: typeof Whisper.ToastView;
+  AlreadyRequestedToJoinToast: typeof Whisper.ToastView;
   BlockedGroupToast: typeof Whisper.ToastView;
   BlockedToast: typeof Whisper.ToastView;
   CannotMixImageAndNonImageAttachmentsToast: typeof Whisper.ToastView;