diff --git a/.eslintrc.js b/.eslintrc.js
index b478bcc3f..f4b59595a 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -40,9 +40,7 @@ module.exports = {
     react: {
       version: 'detect',
     },
-    'import/extensions': [
-      '.js',
-    ],
+    'import/extensions': ['.js', '.jsx', '.ts', '.tsx'],
     'import/ignore': [
       'node_modules',
       '\\.(css|scss|json)$',
@@ -257,9 +255,17 @@ module.exports = {
   overrides: [
     {
       files: ['**/*.tsx'],
-      'rules': {
+      rules: {
         'react/prop-types': 'off',
       },
     },
+    // Disable no-undef in TypeScript
+    // https://stackoverflow.com/a/69155899
+    {
+      files: ['*.ts', '*.tsx'],
+      rules: {
+        'no-undef': 'off',
+      },
+    },
   ],
 };
diff --git a/app/soapbox/normalizers/__tests__/instance-test.js b/app/soapbox/normalizers/__tests__/instance-test.js
index f30f27492..597fbbeee 100644
--- a/app/soapbox/normalizers/__tests__/instance-test.js
+++ b/app/soapbox/normalizers/__tests__/instance-test.js
@@ -8,13 +8,7 @@ describe('normalizeInstance()', () => {
       approval_required: false,
       contact_account: {},
       configuration: {
-        media_attachments: {
-          image_size_limit: 10485760,
-          image_matrix_limit: 16777216,
-          video_size_limit: 41943040,
-          video_frame_rate_limit: 60,
-          video_matrix_limit: 2304000,
-        },
+        media_attachments: {},
         polls: {
           max_options: 4,
           max_characters_per_option: 25,
@@ -48,7 +42,11 @@ describe('normalizeInstance()', () => {
       registrations: false,
       rules: [],
       short_description: '',
-      stats: {},
+      stats: {
+        domain_count: 0,
+        status_count: 0,
+        user_count: 0,
+      },
       title: '',
       thumbnail: '',
       uri: '',
diff --git a/app/soapbox/normalizers/account.js b/app/soapbox/normalizers/account.ts
similarity index 68%
rename from app/soapbox/normalizers/account.js
rename to app/soapbox/normalizers/account.ts
index 9515e1217..f3006f3c2 100644
--- a/app/soapbox/normalizers/account.js
+++ b/app/soapbox/normalizers/account.ts
@@ -1,8 +1,13 @@
-import { Map as ImmutableMap, List as ImmutableList, Record } from 'immutable';
+import {
+  Map as ImmutableMap,
+  List as ImmutableList,
+  Record as ImmutableRecord,
+} from 'immutable';
 
+import { IAccount } from 'soapbox/types';
 import { mergeDefined } from 'soapbox/utils/normalizers';
 
-const AccountRecord = Record({
+const AccountRecord = ImmutableRecord({
   acct: '',
   avatar: '',
   avatar_static: '',
@@ -41,8 +46,8 @@ const AccountRecord = Record({
 });
 
 // https://gitlab.com/soapbox-pub/soapbox-fe/-/issues/549
-const normalizePleromaLegacyFields = account => {
-  return account.update('pleroma', ImmutableMap(), pleroma => {
+const normalizePleromaLegacyFields = (account: ImmutableMap<string, any>) => {
+  return account.update('pleroma', ImmutableMap(), (pleroma: ImmutableMap<string, any>) => {
     return pleroma.withMutations(pleroma => {
       const legacy = ImmutableMap({
         is_active: !pleroma.get('deactivated'),
@@ -57,7 +62,7 @@ const normalizePleromaLegacyFields = account => {
 };
 
 // Normalize Pleroma/Fedibird birthday
-const normalizeBirthday = account => {
+const normalizeBirthday = (account: ImmutableMap<string, any>) => {
   const birthday = [
     account.getIn(['pleroma', 'birthday']),
     account.getIn(['other_settings', 'birthday']),
@@ -66,18 +71,24 @@ const normalizeBirthday = account => {
   return account.set('birthday', birthday);
 };
 
+// Get Pleroma tags
+const getTags = (account: ImmutableMap<string, any>): ImmutableList<any> => {
+  const tags = account.getIn(['pleroma', 'tags']);
+  return ImmutableList(ImmutableList.isList(tags) ? tags : []);
+};
+
 // Normalize Truth Social/Pleroma verified
-const normalizeVerified = account => {
+const normalizeVerified = (account: ImmutableMap<string, any>) => {
   return account.update('verified', verified => {
     return [
       verified === true,
-      account.getIn(['pleroma', 'tags'], ImmutableList()).includes('verified'),
+      getTags(account).includes('verified'),
     ].some(Boolean);
   });
 };
 
 // Normalize Fedibird/Truth Social location
-const normalizeLocation = account => {
+const normalizeLocation = (account: ImmutableMap<string, any>) => {
   return account.update('location', location => {
     return [
       location,
@@ -86,7 +97,7 @@ const normalizeLocation = account => {
   });
 };
 
-export const normalizeAccount = account => {
+export const normalizeAccount = (account: ImmutableMap<string, any>): IAccount => {
   return AccountRecord(
     account.withMutations(account => {
       normalizePleromaLegacyFields(account);
diff --git a/app/soapbox/normalizers/instance.js b/app/soapbox/normalizers/instance.js
index 22f90fc8d..8ec6fde85 100644
--- a/app/soapbox/normalizers/instance.js
+++ b/app/soapbox/normalizers/instance.js
@@ -1,21 +1,19 @@
-import { Map as ImmutableMap, List as ImmutableList, Record } from 'immutable';
+import {
+  Map as ImmutableMap,
+  List as ImmutableList,
+  Record as ImmutableRecord,
+} from 'immutable';
 
 import { parseVersion, PLEROMA } from 'soapbox/utils/features';
 import { mergeDefined } from 'soapbox/utils/normalizers';
 import { isNumber } from 'soapbox/utils/numbers';
 
 // Use Mastodon defaults
-const InstanceRecord = Record({
+const InstanceRecord = ImmutableRecord({
   approval_required: false,
   contact_account: ImmutableMap(),
   configuration: ImmutableMap({
-    media_attachments: ImmutableMap({
-      image_size_limit: 10485760,
-      image_matrix_limit: 16777216,
-      video_size_limit: 41943040,
-      video_frame_rate_limit: 60,
-      video_matrix_limit: 2304000,
-    }),
+    media_attachments: ImmutableMap(),
     polls: ImmutableMap({
       max_options: 4,
       max_characters_per_option: 25,
@@ -49,7 +47,11 @@ const InstanceRecord = Record({
   registrations: false,
   rules: ImmutableList(),
   short_description: '',
-  stats: ImmutableMap(),
+  stats: ImmutableMap({
+    domain_count: 0,
+    status_count: 0,
+    user_count: 0,
+  }),
   title: '',
   thumbnail: '',
   uri: '',
diff --git a/app/soapbox/normalizers/status.js b/app/soapbox/normalizers/status.ts
similarity index 78%
rename from app/soapbox/normalizers/status.js
rename to app/soapbox/normalizers/status.ts
index 494a0ced7..02c9b1f54 100644
--- a/app/soapbox/normalizers/status.js
+++ b/app/soapbox/normalizers/status.ts
@@ -1,9 +1,14 @@
-import { Map as ImmutableMap, List as ImmutableList, Record } from 'immutable';
+import {
+  Map as ImmutableMap,
+  List as ImmutableList,
+  Record as ImmutableRecord,
+} from 'immutable';
 
+import { IStatus } from 'soapbox/types';
 import { accountToMention } from 'soapbox/utils/accounts';
 import { mergeDefined } from 'soapbox/utils/normalizers';
 
-const StatusRecord = Record({
+const StatusRecord = ImmutableRecord({
   account: ImmutableMap(),
   application: null,
   bookmarked: false,
@@ -56,7 +61,7 @@ const basePoll = ImmutableMap({
 
 // Ensure attachments have required fields
 // https://docs.joinmastodon.org/entities/attachment/
-const normalizeAttachment = attachment => {
+const normalizeAttachment = (attachment: ImmutableMap<string, any>) => {
   const url = [
     attachment.get('url'),
     attachment.get('preview_url'),
@@ -72,14 +77,14 @@ const normalizeAttachment = attachment => {
   return attachment.mergeWith(mergeDefined, base);
 };
 
-const normalizeAttachments = status => {
+const normalizeAttachments = (status: ImmutableMap<string, any>) => {
   return status.update('media_attachments', ImmutableList(), attachments => {
     return attachments.map(normalizeAttachment);
   });
 };
 
 // Normalize mentions
-const normalizeMention = mention => {
+const normalizeMention = (mention: ImmutableMap<string, any>) => {
   const base = ImmutableMap({
     acct: '',
     username: (mention.get('acct') || '').split('@')[0],
@@ -89,22 +94,22 @@ const normalizeMention = mention => {
   return mention.mergeWith(mergeDefined, base);
 };
 
-const normalizeMentions = status => {
+const normalizeMentions = (status: ImmutableMap<string, any>) => {
   return status.update('mentions', ImmutableList(), mentions => {
     return mentions.map(normalizeMention);
   });
 };
 
 // Normalize poll option
-const normalizePollOption = option => {
+const normalizePollOption = (option: ImmutableMap<string, any>) => {
   return option.mergeWith(mergeDefined, basePollOption);
 };
 
 // Normalize poll
-const normalizePoll = status => {
+const normalizePoll = (status: ImmutableMap<string, any>) => {
   if (status.hasIn(['poll', 'options'])) {
     return status.update('poll', ImmutableMap(), poll => {
-      return poll.mergeWith(mergeDefined, basePoll).update('options', options => {
+      return poll.mergeWith(mergeDefined, basePoll).update('options', (options: ImmutableList<ImmutableMap<string, any>>) => {
         return options.map(normalizePollOption);
       });
     });
@@ -113,12 +118,12 @@ const normalizePoll = status => {
   }
 };
 // Fix order of mentions
-const fixMentionsOrder = status => {
+const fixMentionsOrder = (status: ImmutableMap<string, any>) => {
   const mentions = status.get('mentions', ImmutableList());
   const inReplyToAccountId = status.get('in_reply_to_account_id');
 
   // Sort the replied-to mention to the top
-  const sorted = mentions.sort((a, b) => {
+  const sorted = mentions.sort((a: ImmutableMap<string, any>, _b: ImmutableMap<string, any>) => {
     if (a.get('id') === inReplyToAccountId) {
       return -1;
     } else {
@@ -130,7 +135,7 @@ const fixMentionsOrder = status => {
 };
 
 // Add self to mentions if it's a reply to self
-const addSelfMention = status => {
+const addSelfMention = (status: ImmutableMap<string, any>) => {
   const accountId = status.getIn(['account', 'id']);
 
   const isSelfReply = accountId === status.get('in_reply_to_account_id');
@@ -147,14 +152,14 @@ const addSelfMention = status => {
 };
 
 // Move the quote to the top-level
-const fixQuote = status => {
+const fixQuote = (status: ImmutableMap<string, any>) => {
   return status.withMutations(status => {
     status.update('quote', quote => quote || status.getIn(['pleroma', 'quote']) || null);
     status.deleteIn(['pleroma', 'quote']);
   });
 };
 
-export const normalizeStatus = status => {
+export const normalizeStatus = (status: ImmutableMap<any, string>): IStatus => {
   return StatusRecord(
     status.withMutations(status => {
       normalizeAttachments(status);
diff --git a/app/soapbox/reducers/__tests__/index-test.js b/app/soapbox/reducers/__tests__/index-test.js
index 2b4a21266..15572f337 100644
--- a/app/soapbox/reducers/__tests__/index-test.js
+++ b/app/soapbox/reducers/__tests__/index-test.js
@@ -7,6 +7,6 @@ describe('root reducer', () => {
     const result = reducer(undefined, {});
     expect(ImmutableRecord.isRecord(result)).toBe(true);
     expect(result.accounts.get('')).toBe(undefined);
-    expect(result.instance.get('version')).toEqual('0.0.0');
+    expect(result.instance.version).toEqual('0.0.0');
   });
 });
diff --git a/app/soapbox/types/account.ts b/app/soapbox/types/account.ts
new file mode 100644
index 000000000..b17935c35
--- /dev/null
+++ b/app/soapbox/types/account.ts
@@ -0,0 +1,44 @@
+/**
+ * Account entity.
+ * https://docs.joinmastodon.org/entities/account/
+ **/
+
+interface IAccount {
+  acct: string;
+  avatar: string;
+  avatar_static: string;
+  birthday: Date | undefined;
+  bot: boolean;
+  created_at: Date;
+  display_name: string;
+  emojis: Iterable<any>;
+  fields: Iterable<any>;
+  followers_count: number;
+  following_count: number;
+  fqn: string;
+  header: string;
+  header_static: string;
+  id: string;
+  last_status_at: Date;
+  location: string;
+  locked: boolean;
+  moved: null;
+  note: string;
+  pleroma: Record<any, any>;
+  source: Record<any, any>;
+  statuses_count: number;
+  uri: string;
+  url: string;
+  username: string;
+  verified: boolean;
+
+  // Internal fields
+  display_name_html: string;
+  note_emojified: string;
+  note_plain: string;
+  patron: Record<any, any>;
+  relationship: Iterable<any>;
+  should_refetch: boolean;
+}
+
+export { IAccount };
diff --git a/app/soapbox/types/index.ts b/app/soapbox/types/index.ts
new file mode 100644
index 000000000..df14c2720
--- /dev/null
+++ b/app/soapbox/types/index.ts
@@ -0,0 +1,4 @@
+import { IAccount } from './account';
+import { IStatus } from './status';
+
+export { IAccount, IStatus };
diff --git a/app/soapbox/types/status.ts b/app/soapbox/types/status.ts
new file mode 100644
index 000000000..a1a1ed061
--- /dev/null
+++ b/app/soapbox/types/status.ts
@@ -0,0 +1,45 @@
+/**
+ * Status entity.
+ * https://docs.joinmastodon.org/entities/status/
+ **/
+
+interface IStatus {
+  account: Record<any, any>;
+  application: Record<string, any> | null;
+  bookmarked: boolean;
+  card: Record<string, any> | null;
+  content: string;
+  created_at: Date;
+  emojis: Iterable<any>;
+  favourited: boolean;
+  favourites_count: number;
+  in_reply_to_account_id: string | null;
+  in_reply_to_id: string | null;
+  id: string;
+  language: null;
+  media_attachments: Iterable<any>;
+  mentions: Iterable<any>;
+  muted: boolean;
+  pinned: boolean;
+  pleroma: Record<string, any>;
+  poll: null;
+  quote: null;
+  reblog: null;
+  reblogged: boolean;
+  reblogs_count: number;
+  replies_count: number;
+  sensitive: boolean;
+  spoiler_text: string;
+  tags: Iterable<any>;
+  uri: string;
+  url: string;
+  visibility: string;
+
+  // Internal fields
+  contentHtml: string;
+  hidden: boolean;
+  search_index: string;
+  spoilerHtml: string;
+}
+
+export { IStatus };