diff --git a/web/src/fetch_status.js b/web/src/fetch_status.ts
similarity index 86%
rename from web/src/fetch_status.js
rename to web/src/fetch_status.ts
index 13456e3597..49265ae312 100644
--- a/web/src/fetch_status.js
+++ b/web/src/fetch_status.ts
@@ -1,6 +1,7 @@
 import * as message_feed_loading from "./message_feed_loading";
+import type {RawMessage} from "./types";
 
-function max_id_for_messages(messages) {
+function max_id_for_messages(messages: RawMessage[]): number {
     let max_id = 0;
     for (const msg of messages) {
         max_id = Math.max(max_id, msg.id);
@@ -29,14 +30,18 @@ export class FetchStatus {
     // (described in detail below).
     _expected_max_message_id = 0;
 
-    start_older_batch(opts) {
+    start_older_batch(opts: {update_loading_indicator: boolean}): void {
         this._loading_older = true;
         if (opts.update_loading_indicator) {
             message_feed_loading.show_loading_older();
         }
     }
 
-    finish_older_batch(opts) {
+    finish_older_batch(opts: {
+        found_oldest: boolean;
+        history_limited: boolean;
+        update_loading_indicator: boolean;
+    }): void {
         this._loading_older = false;
         this._found_oldest = opts.found_oldest;
         this._history_limited = opts.history_limited;
@@ -45,26 +50,29 @@ export class FetchStatus {
         }
     }
 
-    can_load_older_messages() {
+    can_load_older_messages(): boolean {
         return !this._loading_older && !this._found_oldest;
     }
 
-    has_found_oldest() {
+    has_found_oldest(): boolean {
         return this._found_oldest;
     }
 
-    history_limited() {
+    history_limited(): boolean {
         return this._history_limited;
     }
 
-    start_newer_batch(opts) {
+    start_newer_batch(opts: {update_loading_indicator: boolean}): void {
         this._loading_newer = true;
         if (opts.update_loading_indicator) {
             message_feed_loading.show_loading_newer();
         }
     }
 
-    finish_newer_batch(messages, opts) {
+    finish_newer_batch(
+        messages: RawMessage[],
+        opts: {update_loading_indicator: boolean; found_newest: boolean},
+    ): boolean {
         // Returns true if and only if the caller needs to trigger an
         // additional fetch due to the race described below.
         const found_max_message_id = max_id_for_messages(messages);
@@ -119,15 +127,15 @@ export class FetchStatus {
         return false;
     }
 
-    can_load_newer_messages() {
+    can_load_newer_messages(): boolean {
         return !this._loading_newer && !this._found_newest;
     }
 
-    has_found_newest() {
+    has_found_newest(): boolean {
         return this._found_newest;
     }
 
-    update_expected_max_message_id(messages) {
+    update_expected_max_message_id(messages: RawMessage[]): void {
         this._expected_max_message_id = Math.max(
             this._expected_max_message_id,
             max_id_for_messages(messages),
diff --git a/web/src/types.ts b/web/src/types.ts
index 78122d1db2..e424eed89b 100644
--- a/web/src/types.ts
+++ b/web/src/types.ts
@@ -6,18 +6,73 @@ export type MatchedMessage = {
 
 // TODO/typescript: Move this to message_store
 export type MessageType = "private" | "stream";
+export type MessageReactionType = "unicode_emoji" | "realm_emoji" | "zulip_extra_emoji";
+
+// TODO/typescript: Move these types to message_store
+
+export type DisplayRecipientUser = {
+    email: string;
+    full_name: string;
+    id: number;
+    is_mirror_dummy: boolean;
+};
+
+export type DisplayRecipient = string | DisplayRecipientUser[];
+
+export type MessageEditHistoryEntry = {
+    user_id: number | null;
+    timestamp: number;
+    prev_content?: string;
+    prev_rendered_content?: string;
+    prev_rendered_content_version?: number;
+    prev_stream?: number;
+    prev_topic?: string;
+    stream?: number;
+    topic?: string;
+};
+
+export type MessageReaction = {
+    emoji_name: string;
+    emoji_code: string;
+    reaction_type: MessageReactionType;
+    user_id: number;
+};
+
+// TODO/typescript: Move this to server_events
+export type TopicLink = {
+    text: string;
+    url: string;
+};
 
 // TODO/typescript: Move this to message_store
 export type RawMessage = {
+    avatar_url: string | null;
+    client: string;
+    content: string;
+    content_type: "text/html";
+    display_recipient: DisplayRecipient;
+    edit_history?: MessageEditHistoryEntry[];
+    id: number;
+    is_me_message: boolean;
+    last_edit_timestamp?: number;
+    reactions: MessageReaction[];
+    recipient_id: number;
     sender_email: string;
-    stream_id: number;
+    sender_full_name: string;
+    sender_id: number;
+    sender_realm_str: string;
+    stream_id?: number;
     subject: string;
+    submessages: string[];
+    timestamp: number;
+    topic_links: TopicLink[];
     type: MessageType;
+    flags: string[];
 } & MatchedMessage;
 
 // TODO/typescript: Move this to message_store
 export type Message = RawMessage & {
-    to_user_ids: string;
+    to_user_ids?: string;
     topic: string;
 };
 
@@ -32,12 +87,6 @@ export type UserGroupUpdateEvent = {
     };
 };
 
-// TODO/typescript: Move this to server_events
-export type TopicLink = {
-    text: string;
-    url: string;
-};
-
 // TODO/typescript: Move this to server_events
 export type UpdateMessageEvent = {
     id: number;