diff --git a/web/database/database-module-provider.js b/web/database/database-module-provider.js
--- a/web/database/database-module-provider.js
+++ b/web/database/database-module-provider.js
@@ -131,7 +131,9 @@
 }
 
 async function getSafariEncryptionKey(): Promise<SubtleCrypto$JsonWebKey> {
-  const encryptionKey = await localforage.getItem(SQLITE_ENCRYPTION_KEY);
+  const encryptionKey = await localforage.getItem<CryptoKey>(
+    SQLITE_ENCRYPTION_KEY,
+  );
   if (encryptionKey) {
     return await exportKeyToJWK(encryptionKey);
   }
diff --git a/web/database/utils/worker-crypto-utils.js b/web/database/utils/worker-crypto-utils.js
--- a/web/database/utils/worker-crypto-utils.js
+++ b/web/database/utils/worker-crypto-utils.js
@@ -6,7 +6,7 @@
   'decrypt',
 ];
 
-type EncryptedData = {
+export type EncryptedData = {
   +iv: BufferSource,
   +ciphertext: Uint8Array,
 };
diff --git a/web/database/worker/db-worker.js b/web/database/worker/db-worker.js
--- a/web/database/worker/db-worker.js
+++ b/web/database/worker/db-worker.js
@@ -35,6 +35,7 @@
   encryptDatabaseFile,
   generateDatabaseCryptoKey,
   importJWKKey,
+  type EncryptedData,
 } from '../utils/worker-crypto-utils.js';
 
 localforage.config(localforageConfig);
@@ -74,7 +75,9 @@
     }
   }
 
-  const encryptedContent = await localforage.getItem(SQLITE_CONTENT);
+  const encryptedContent = await localforage.getItem<EncryptedData>(
+    SQLITE_CONTENT,
+  );
 
   let dbContent = null;
   try {
diff --git a/web/input/input-state-container.react.js b/web/input/input-state-container.react.js
--- a/web/input/input-state-container.react.js
+++ b/web/input/input-state-container.react.js
@@ -232,7 +232,7 @@
   }
 
   static completedMessageIDs(state: State): Set<string> {
-    const completed = new Map();
+    const completed = new Map<string, boolean>();
     for (const threadID in state.pendingUploads) {
       const pendingUploads = state.pendingUploads[threadID];
       for (const localUploadID in pendingUploads) {
@@ -250,7 +250,7 @@
         }
       }
     }
-    const messageIDs = new Set();
+    const messageIDs = new Set<string>();
     for (const [messageID, isCompleted] of completed) {
       if (isCompleted) {
         messageIDs.add(messageID);
@@ -265,7 +265,7 @@
       return;
     }
 
-    const previouslyAssignedMessageIDs = new Set();
+    const previouslyAssignedMessageIDs = new Set<string>();
     for (const threadID in prevState.pendingUploads) {
       const pendingUploads = prevState.pendingUploads[threadID];
       for (const localUploadID in pendingUploads) {
@@ -276,7 +276,14 @@
       }
     }
 
-    const newlyAssignedUploads = new Map();
+    const newlyAssignedUploads = new Map<
+      string,
+      {
+        +threadID: string,
+        +shouldEncrypt: boolean,
+        +uploads: PendingMultimediaUpload[],
+      },
+    >();
     for (const threadID in this.state.pendingUploads) {
       const pendingUploads = this.state.pendingUploads[threadID];
       for (const localUploadID in pendingUploads) {
@@ -306,7 +313,7 @@
       }
     }
 
-    const newMessageInfos = new Map();
+    const newMessageInfos = new Map<string, RawMultimediaMessageInfo>();
     for (const [messageID, assignedUploads] of newlyAssignedUploads) {
       const { uploads, threadID, shouldEncrypt } = assignedUploads;
       const creatorID = this.props.viewerID;
@@ -1524,7 +1531,7 @@
       payload: newRawMessageInfo,
     });
 
-    const uploadIDsToRetry = new Set();
+    const uploadIDsToRetry = new Set<string>();
     const uploadsToRetry = [];
     for (const pendingUpload of pendingUploads) {
       const { serverID, messageID, localID, abort } = pendingUpload;
@@ -1657,7 +1664,7 @@
       [],
     );
     const textMessageCreationSideEffectsFunc =
-      useMessageCreationSideEffectsFunc(messageTypes.TEXT);
+      useMessageCreationSideEffectsFunc<RawTextMessageInfo>(messageTypes.TEXT);
 
     return (
       <InputStateContainer
diff --git a/web/media/aes-crypto-utils.test.js b/web/media/aes-crypto-utils.test.js
--- a/web/media/aes-crypto-utils.test.js
+++ b/web/media/aes-crypto-utils.test.js
@@ -15,7 +15,7 @@
 ]);
 
 const randomData = new Uint8Array(
-  new Array(100).fill(0).map(() => Math.floor(Math.random() * 255)),
+  new Array<number>(100).fill(0).map(() => Math.floor(Math.random() * 255)),
 );
 
 describe('generateKey', () => {
diff --git a/web/modals/chat/message-results-modal.react.js b/web/modals/chat/message-results-modal.react.js
--- a/web/modals/chat/message-results-modal.react.js
+++ b/web/modals/chat/message-results-modal.react.js
@@ -89,7 +89,10 @@
     // By the nature of using messageListData and passing in
     // the desired translatedMessageResults as additional
     // messages, we will have duplicate ChatMessageInfoItems.
-    const uniqueChatMessageInfoItemsMap = new Map();
+    const uniqueChatMessageInfoItemsMap = new Map<
+      string,
+      ChatMessageInfoItem,
+    >();
     chatMessageInfoItems.forEach(
       item =>
         item.messageInfo &&
@@ -102,8 +105,12 @@
     // in the order of pin_time (newest first).
     const sortedChatMessageInfoItems = [];
     for (let i = 0; i < rawMessageResults.length; i++) {
+      const rawMessageID = rawMessageResults[i].id;
+      if (!rawMessageID) {
+        continue;
+      }
       sortedChatMessageInfoItems.push(
-        uniqueChatMessageInfoItemsMap.get(rawMessageResults[i].id),
+        uniqueChatMessageInfoItemsMap.get(rawMessageID),
       );
     }
 
diff --git a/web/roles/community-roles-modal.react.js b/web/roles/community-roles-modal.react.js
--- a/web/roles/community-roles-modal.react.js
+++ b/web/roles/community-roles-modal.react.js
@@ -5,6 +5,7 @@
 import { useModalContext } from 'lib/components/modal-provider.react.js';
 import { threadInfoSelector } from 'lib/selectors/thread-selectors.js';
 import { useRoleMemberCountsForCommunity } from 'lib/shared/thread-utils.js';
+import type { UserSurfacedPermission } from 'lib/types/thread-permission-types.js';
 import type { ThreadInfo } from 'lib/types/thread-types.js';
 
 import css from './community-roles-modal.css';
@@ -49,7 +50,10 @@
     [roleNamesToMembers, threadInfo],
   );
 
-  const rolePermissionsForNewRole = React.useMemo(() => new Set(), []);
+  const rolePermissionsForNewRole = React.useMemo(
+    () => new Set<UserSurfacedPermission>(),
+    [],
+  );
 
   const onClickCreateRole = React.useCallback(
     () =>
diff --git a/web/search/message-search-state-provider.react.js b/web/search/message-search-state-provider.react.js
--- a/web/search/message-search-state-provider.react.js
+++ b/web/search/message-search-state-provider.react.js
@@ -37,7 +37,7 @@
     [threadID: string]: $ReadOnlyArray<RawMessageInfo>,
   }>({});
 
-  const endsReached = React.useRef(new Set());
+  const endsReached = React.useRef(new Set<string>());
 
   const lastIDs = React.useRef<{
     [threadID: string]: string,