diff --git a/tsconfig.json b/tsconfig.json
index 07dd0a313c..74ea340173 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -22,6 +22,7 @@
 
         /* Strict type-checking */
         "strict": true,
+        "exactOptionalPropertyTypes": true,
         "forceConsistentCasingInFileNames": true,
         "isolatedModules": true,
         "noImplicitOverride": true,
diff --git a/web/debug-require-webpack-plugin.ts b/web/debug-require-webpack-plugin.ts
index c3c8b8b6fc..d0233b2a9b 100644
--- a/web/debug-require-webpack-plugin.ts
+++ b/web/debug-require-webpack-plugin.ts
@@ -13,7 +13,7 @@ export default class DebugRequirePlugin implements WebpackPluginInstance {
         const resolved = new Map<string, Set<string>>();
         const nameSymbol = Symbol("DebugRequirePluginName");
         type NamedRequest = ResolveRequest & {
-            [nameSymbol]?: string;
+            [nameSymbol]?: string | undefined;
         };
         let debugRequirePath: string | false = false;
 
diff --git a/web/e2e-tests/lib/common.ts b/web/e2e-tests/lib/common.ts
index 2244aa503f..79fff78a48 100644
--- a/web/e2e-tests/lib/common.ts
+++ b/web/e2e-tests/lib/common.ts
@@ -628,9 +628,9 @@ export async function run_test_async(test_function: (page: Page) => Promise<void
             columnNumber,
         }: ConsoleMessageLocation): Promise<string> => {
             let frame = new StackFrame({
-                fileName: url,
-                lineNumber: lineNumber === undefined ? undefined : lineNumber + 1,
-                columnNumber: columnNumber === undefined ? undefined : columnNumber + 1,
+                ...(url !== undefined && {fileName: url}),
+                ...(lineNumber !== undefined && {lineNumber: lineNumber + 1}),
+                ...(columnNumber !== undefined && {columnNumber: columnNumber + 1}),
             });
             try {
                 frame = await gps.getMappedLocation(frame);
diff --git a/web/src/blueslip_stacktrace.ts b/web/src/blueslip_stacktrace.ts
index 38bdea376f..6c8706abb6 100644
--- a/web/src/blueslip_stacktrace.ts
+++ b/web/src/blueslip_stacktrace.ts
@@ -28,11 +28,11 @@ type NumberedLine = {
 };
 
 type CleanStackFrame = {
-    full_path?: string;
-    show_path?: string;
-    function_name?: FunctionName;
-    line_number?: number;
-    context?: NumberedLine[];
+    full_path: string | undefined;
+    show_path: string | undefined;
+    function_name: FunctionName | undefined;
+    line_number: number | undefined;
+    context: NumberedLine[] | undefined;
 };
 
 export function exception_msg(
diff --git a/web/src/bootstrap_typeahead.ts b/web/src/bootstrap_typeahead.ts
index dee623a9f7..f0ae7117ed 100644
--- a/web/src/bootstrap_typeahead.ts
+++ b/web/src/bootstrap_typeahead.ts
@@ -215,7 +215,7 @@ export class Typeahead<ItemType extends string | object> {
     dropup: boolean;
     automated: () => boolean;
     trigger_selection: (event: JQuery.KeyDownEvent) => boolean;
-    on_escape?: () => void;
+    on_escape: (() => void) | undefined;
     // returns a string to show in typeahead header or false.
     header_html: () => string | false;
     // returns a string to show in typeahead items or false.
@@ -224,16 +224,16 @@ export class Typeahead<ItemType extends string | object> {
     query = "";
     mouse_moved_since_typeahead = false;
     shown = false;
-    openInputFieldOnKeyUp?: () => void;
-    closeInputFieldOnHide?: () => void;
+    openInputFieldOnKeyUp: (() => void) | undefined;
+    closeInputFieldOnHide: (() => void) | undefined;
     helpOnEmptyStrings: boolean;
     tabIsEnter: boolean;
     naturalSearch: boolean;
     stopAdvance: boolean;
     advanceKeyCodes: number[];
-    parentElement?: string;
+    parentElement: string | undefined;
     values: WeakMap<HTMLElement, ItemType>;
-    instance?: Instance;
+    instance: Instance | undefined;
 
     constructor(input_element: TypeaheadInputElement, options: TypeaheadOptions<ItemType>) {
         this.input_element = input_element;
diff --git a/web/src/buddy_data.ts b/web/src/buddy_data.ts
index 11fed91544..e071ed0074 100644
--- a/web/src/buddy_data.ts
+++ b/web/src/buddy_data.ts
@@ -204,7 +204,7 @@ export function get_title_data(
     is_group: boolean,
 ): {
     first_line: string;
-    second_line?: string;
+    second_line: string | undefined;
     third_line: string;
     show_you?: boolean;
 } {
diff --git a/web/src/channel.ts b/web/src/channel.ts
index e34b5c6f48..d5d914048c 100644
--- a/web/src/channel.ts
+++ b/web/src/channel.ts
@@ -14,17 +14,19 @@ import * as spectators from "./spectators";
 type AjaxRequestHandlerOptions = Omit<JQuery.AjaxSettings, "success"> & {
     url: string;
     ignore_reload?: boolean;
-    success?: (
-        data: unknown,
-        textStatus: JQuery.Ajax.SuccessTextStatus,
-        jqXHR: JQuery.jqXHR<unknown>,
-    ) => void;
+    success?:
+        | ((
+              data: unknown,
+              textStatus: JQuery.Ajax.SuccessTextStatus,
+              jqXHR: JQuery.jqXHR<unknown>,
+          ) => void)
+        | undefined;
     error?: JQuery.Ajax.ErrorCallback<unknown>;
 };
 
 type PatchRequestData =
     | {processData: false; data: FormData}
-    | {processData?: true; data: Record<string, unknown>};
+    | {processData?: true | undefined; data: Record<string, unknown>};
 
 export type AjaxRequestHandler = typeof call | typeof patch;
 
diff --git a/web/src/compose_actions.ts b/web/src/compose_actions.ts
index b6662cb993..3ba5686c36 100644
--- a/web/src/compose_actions.ts
+++ b/web/src/compose_actions.ts
@@ -33,14 +33,14 @@ type ComposeActionsStartOpts = {
     force_close?: boolean;
     trigger?: string;
     private_message_recipient?: string;
-    message?: Message;
-    stream_id?: number;
+    message?: Message | undefined;
+    stream_id?: number | undefined;
     topic?: string;
     content?: string;
     draft_id?: string;
     skip_scrolling_selected_message?: boolean;
     is_reply?: boolean;
-    keep_composebox_empty?: boolean;
+    keep_composebox_empty?: boolean | undefined;
 };
 
 // An iteration on `ComposeActionsStartOpts` that enforces that
diff --git a/web/src/compose_closed_ui.ts b/web/src/compose_closed_ui.ts
index bc94fac7bf..974ad8ed44 100644
--- a/web/src/compose_closed_ui.ts
+++ b/web/src/compose_closed_ui.ts
@@ -18,9 +18,9 @@ function format_stream_recipient_label(stream_id: number, topic: string): string
 }
 
 type ComposeClosedMessage = {
-    stream_id?: number;
+    stream_id?: number | undefined;
     topic?: string;
-    display_reply_to?: string;
+    display_reply_to?: string | undefined;
 };
 
 export function get_recipient_label(message?: ComposeClosedMessage): string {
diff --git a/web/src/compose_reply.ts b/web/src/compose_reply.ts
index 9cb1ce2b89..76030c5ac5 100644
--- a/web/src/compose_reply.ts
+++ b/web/src/compose_reply.ts
@@ -146,8 +146,8 @@ export function respond_to_message(opts: {
         message_type: msg_type,
         stream_id,
         topic,
-        private_message_recipient: pm_recipient,
-        trigger: opts.trigger,
+        ...(pm_recipient !== undefined && {private_message_recipient: pm_recipient}),
+        ...(opts.trigger !== undefined && {trigger: opts.trigger}),
         is_reply: true,
         keep_composebox_empty: opts.keep_composebox_empty,
     });
diff --git a/web/src/compose_ui.ts b/web/src/compose_ui.ts
index 7ff5a16fa6..1cd705cc13 100644
--- a/web/src/compose_ui.ts
+++ b/web/src/compose_ui.ts
@@ -31,7 +31,7 @@ export type ComposeTriggeredOptions = {
     | {
           message_type: "stream";
           topic: string;
-          stream_id?: number;
+          stream_id?: number | undefined;
       }
     | {
           message_type: "private";
diff --git a/web/src/drafts.ts b/web/src/drafts.ts
index 7683e457b0..13488b068e 100644
--- a/web/src/drafts.ts
+++ b/web/src/drafts.ts
@@ -555,7 +555,7 @@ type FormattedDraft =
     | {
           is_stream: true;
           draft_id: string;
-          stream_name?: string;
+          stream_name?: string | undefined;
           recipient_bar_color: string;
           stream_privacy_icon_color: string;
           topic: string;
diff --git a/web/src/dropdown_widget.ts b/web/src/dropdown_widget.ts
index a99f57cdcc..68d8f87455 100644
--- a/web/src/dropdown_widget.ts
+++ b/web/src/dropdown_widget.ts
@@ -59,7 +59,7 @@ type DropdownWidgetOptions = {
     focus_target_on_hidden?: boolean;
     tippy_props?: Partial<tippy.Props>;
     // NOTE: Any value other than `undefined` will be rendered when class is initialized.
-    default_id?: string | number;
+    default_id?: string | number | undefined;
     unique_id_type?: DataTypes;
     // Text to show if the current value is not in `get_options()`.
     text_if_current_value_not_in_options?: string;
diff --git a/web/src/filter.ts b/web/src/filter.ts
index 7c3df5dad5..31b7209be4 100644
--- a/web/src/filter.ts
+++ b/web/src/filter.ts
@@ -243,7 +243,7 @@ function message_matches_search_term(message: Message, operator: string, operand
 
 export class Filter {
     _terms: NarrowTerm[];
-    _sub?: StreamSubscription;
+    _sub?: StreamSubscription | undefined;
     _sorted_term_types?: string[] = undefined;
     _predicate?: (message: Message) => boolean;
     _can_mark_messages_read?: boolean;
@@ -914,8 +914,8 @@ export class Filter {
 
     add_icon_data(context: {
         title: string;
-        description?: string;
-        link?: string;
+        description?: string | undefined;
+        link?: string | undefined;
         is_spectator: boolean;
     }): IconData {
         // We have special icons for the simple narrows available for the via sidebars.
diff --git a/web/src/inbox_ui.ts b/web/src/inbox_ui.ts
index 8b748b97bc..8cc69084cf 100644
--- a/web/src/inbox_ui.ts
+++ b/web/src/inbox_ui.ts
@@ -860,7 +860,7 @@ function update_closed_compose_text($row: JQuery, is_header_row: boolean): void
     compose_closed_ui.update_reply_recipient_label(message);
 }
 
-export function get_focused_row_message(): {message?: Message} & (
+export function get_focused_row_message(): {message?: Message | undefined} & (
     | {msg_type: "private"; private_message_recipient?: string}
     | {msg_type: "stream"; stream_id: number; topic?: string}
     | {msg_type?: never}
@@ -893,6 +893,7 @@ export function get_focused_row_message(): {message?: Message} & (
         const message = message_store.get(row_info.latest_msg_id);
         if (message === undefined) {
             const recipients = people.user_ids_string_to_emails_string(row_info.user_ids_string);
+            assert(recipients !== undefined);
             return {
                 msg_type: "private",
                 private_message_recipient: recipients,
diff --git a/web/src/input_pill.ts b/web/src/input_pill.ts
index ae5d4af91d..e5b5e8f18b 100644
--- a/web/src/input_pill.ts
+++ b/web/src/input_pill.ts
@@ -17,7 +17,7 @@ export type InputPillItem<T> = {
     type: string;
     img_src?: string;
     deactivated?: boolean;
-    status_emoji_info?: EmojiRenderingDetails & {emoji_alt_code?: boolean}; // TODO: Move this in user_status.js
+    status_emoji_info?: (EmojiRenderingDetails & {emoji_alt_code?: boolean}) | undefined; // TODO: Move this in user_status.js
     should_add_guest_user_indicator?: boolean;
 } & T;
 
@@ -58,11 +58,11 @@ type InputPillStore<T> = {
 type InputPillRenderingDetails = {
     display_value: string;
     has_image: boolean;
-    img_src?: string;
-    deactivated?: boolean;
+    img_src?: string | undefined;
+    deactivated: boolean | undefined;
     has_status?: boolean;
-    status_emoji_info?: EmojiRenderingDetails & {emoji_alt_code?: boolean};
-    should_add_guest_user_indicator?: boolean;
+    status_emoji_info?: (EmojiRenderingDetails & {emoji_alt_code?: boolean}) | undefined;
+    should_add_guest_user_indicator: boolean | undefined;
 };
 
 // These are the functions that are exposed to other modules.
diff --git a/web/src/list_cursor.ts b/web/src/list_cursor.ts
index 99373abc8b..bb2b8cce9b 100644
--- a/web/src/list_cursor.ts
+++ b/web/src/list_cursor.ts
@@ -14,7 +14,7 @@ type List<Key> = {
 export class ListCursor<Key> {
     highlight_class: string;
     list: List<Key>;
-    curr_key?: Key;
+    curr_key?: Key | undefined;
 
     constructor({highlight_class, list}: {highlight_class: string; list: List<Key>}) {
         this.highlight_class = highlight_class;
diff --git a/web/src/loading.ts b/web/src/loading.ts
index 9b14b9737f..1d74935121 100644
--- a/web/src/loading.ts
+++ b/web/src/loading.ts
@@ -11,7 +11,12 @@ export function make_indicator(
         text,
         width,
         height,
-    }: {abs_positioned?: boolean; text?: string; width?: number; height?: number} = {},
+    }: {
+        abs_positioned?: boolean;
+        text?: string;
+        width?: number | undefined;
+        height?: number | undefined;
+    } = {},
 ): void {
     let $container = $outer_container;
 
diff --git a/web/src/message_edit_history.ts b/web/src/message_edit_history.ts
index 0da8ca661a..c0759802fc 100644
--- a/web/src/message_edit_history.ts
+++ b/web/src/message_edit_history.ts
@@ -30,15 +30,15 @@ type EditHistoryEntry = {
     edited_by_notice: string;
     timestamp: number; // require to set data-message-id for overlay message row
     is_stream: boolean;
-    recipient_bar_color?: string;
-    body_to_render?: string;
-    topic_edited?: boolean;
-    prev_topic?: string;
-    new_topic?: string;
-    stream_changed?: boolean;
-    prev_stream?: string;
-    prev_stream_id?: number;
-    new_stream?: string;
+    recipient_bar_color: string | undefined;
+    body_to_render: string | undefined;
+    topic_edited: boolean | undefined;
+    prev_topic: string | undefined;
+    new_topic: string | undefined;
+    stream_changed: boolean | undefined;
+    prev_stream: string | undefined;
+    prev_stream_id: number | undefined;
+    new_stream: string | undefined;
 };
 
 const server_message_history_schema = z.object({
diff --git a/web/src/message_store.ts b/web/src/message_store.ts
index 1b4037cb03..7b3e52f71c 100644
--- a/web/src/message_store.ts
+++ b/web/src/message_store.ts
@@ -7,8 +7,8 @@ import type {UserStatusEmojiInfo} from "./user_status";
 const stored_messages = new Map<number, Message>();
 
 export type MatchedMessage = {
-    match_content?: string;
-    match_subject?: string;
+    match_content?: string | undefined;
+    match_subject?: string | undefined;
 };
 
 export type MessageReactionType = "unicode_emoji" | "realm_emoji" | "zulip_extra_emoji";
@@ -130,7 +130,7 @@ export type Message = (
     flags?: string[];
 
     small_avatar_url?: string; // Used in `message_avatar.hbs`
-    status_emoji_info?: UserStatusEmojiInfo; // Used in `message_body.hbs`
+    status_emoji_info?: UserStatusEmojiInfo | undefined; // Used in `message_body.hbs`
 } & (
         | {
               type: "private";
diff --git a/web/src/modals.ts b/web/src/modals.ts
index 9d7c31105f..6841a03f75 100644
--- a/web/src/modals.ts
+++ b/web/src/modals.ts
@@ -10,9 +10,9 @@ type Hook = () => void;
 export type ModalConfig = {
     autoremove?: boolean;
     on_show?: () => void;
-    on_shown?: () => void;
-    on_hide?: () => void;
-    on_hidden?: () => void;
+    on_shown?: (() => void) | undefined;
+    on_hide?: (() => void) | undefined;
+    on_hidden?: (() => void) | undefined;
 };
 
 const pre_open_hooks: Hook[] = [];
diff --git a/web/src/narrow_state.ts b/web/src/narrow_state.ts
index d75b6d989f..8e486ab0b5 100644
--- a/web/src/narrow_state.ts
+++ b/web/src/narrow_state.ts
@@ -101,8 +101,9 @@ export function set_compose_defaults(): {
         }
     }
 
-    if (single.has("topic")) {
-        opts.topic = single.get("topic");
+    const topic = single.get("topic");
+    if (topic !== undefined) {
+        opts.topic = topic;
     }
 
     const private_message_recipient = single.get("dm");
diff --git a/web/src/people.ts b/web/src/people.ts
index 828f1e7e7b..8bba9f2096 100644
--- a/web/src/people.ts
+++ b/web/src/people.ts
@@ -20,7 +20,7 @@ import * as util from "./util";
 
 export type ProfileData = {
     value: string;
-    rendered_value?: string;
+    rendered_value?: string | undefined;
 };
 
 export type User = {
@@ -29,7 +29,7 @@ export type User = {
     email: string;
     full_name: string;
     // used for caching result of remove_diacritics.
-    name_with_diacritics_removed?: string;
+    name_with_diacritics_removed?: string | undefined;
     date_joined: string;
     is_active: boolean;
     is_owner: boolean;
@@ -1489,7 +1489,6 @@ export function make_user(user_id: number, email: string, full_name: string): Us
         // We explicitly don't set `avatar_url` for fake person objects so that fallback code
         // will ask the server or compute a gravatar URL only once we need the avatar URL,
         // it's important for performance that we not hash every user's email to get gravatar URLs.
-        avatar_url: undefined,
         avatar_version: 0,
         timezone: "",
         date_joined: "",
diff --git a/web/src/pm_list_data.ts b/web/src/pm_list_data.ts
index 9e28b4e743..079d4536bf 100644
--- a/web/src/pm_list_data.ts
+++ b/web/src/pm_list_data.ts
@@ -38,8 +38,8 @@ type DisplayObject = {
     is_zero: boolean;
     is_active: boolean;
     url: string;
-    status_emoji_info?: UserStatusEmojiInfo;
-    user_circle_class?: string;
+    status_emoji_info: UserStatusEmojiInfo | undefined;
+    user_circle_class: string | undefined;
     is_group: boolean;
     is_bot: boolean;
 };
diff --git a/web/src/poll_widget.ts b/web/src/poll_widget.ts
index 10dd4940b7..6533e5f795 100644
--- a/web/src/poll_widget.ts
+++ b/web/src/poll_widget.ts
@@ -19,8 +19,8 @@ import * as people from "./people";
 export type Event = {sender_id: number; data: InboundData};
 
 export type PollWidgetExtraData = {
-    question?: string;
-    options?: string[];
+    question?: string | undefined;
+    options?: string[] | undefined;
 };
 
 export function activate({
diff --git a/web/src/presence.ts b/web/src/presence.ts
index 242d4b25b0..4fac916208 100644
--- a/web/src/presence.ts
+++ b/web/src/presence.ts
@@ -4,13 +4,13 @@ import {user_settings} from "./user_settings";
 
 export type RawPresence = {
     server_timestamp: number;
-    active_timestamp?: number;
-    idle_timestamp?: number;
+    active_timestamp?: number | undefined;
+    idle_timestamp?: number | undefined;
 };
 
 export type PresenceStatus = {
     status: "active" | "idle" | "offline";
-    last_active?: number;
+    last_active?: number | undefined;
 };
 
 export type PresenceInfoFromEvent = {
diff --git a/web/src/settings_invites.ts b/web/src/settings_invites.ts
index 545d00e11d..be1a095a90 100644
--- a/web/src/settings_invites.ts
+++ b/web/src/settings_invites.ts
@@ -39,7 +39,7 @@ export const invite_schema = z.intersection(
     ]),
 );
 type Invite = z.output<typeof invite_schema> & {
-    invited_as_text?: string;
+    invited_as_text?: string | undefined;
     invited_absolute_time?: string;
     expiry_date_absolute_time?: string;
     is_admin?: boolean;
diff --git a/web/src/stats/stats.ts b/web/src/stats/stats.ts
index 5b0b12b2ad..889e47b1a6 100644
--- a/web/src/stats/stats.ts
+++ b/web/src/stats/stats.ts
@@ -704,10 +704,10 @@ function populate_messages_sent_by_client(raw_data: unknown): void {
 
     const layout: Partial<Plotly.Layout> = {
         width: 750,
-        height: undefined, // set in draw_plot()
+        // height set in draw_plot()
         margin: {l: 10, r: 10, b: 40, t: 10},
         font: font_14pt,
-        xaxis: {range: undefined}, // set in draw_plot()
+        // xaxis set in draw_plot()
         yaxis: {showticklabels: false},
         showlegend: false,
     };
@@ -813,7 +813,7 @@ function populate_messages_sent_by_client(raw_data: unknown): void {
         $("#id_messages_sent_by_client > div").removeClass("spinner");
         const data_ = plot_data[user_button][time_button];
         layout.height = layout.margin!.b! + data_.trace.x.length * 30;
-        layout.xaxis!.range = [0, Math.max(...data_.trace.x) * 1.3];
+        layout.xaxis = {range: [0, Math.max(...data_.trace.x) * 1.3]};
         void Plotly.newPlot(
             "id_messages_sent_by_client",
             [data_.trace, data_.trace_annotations],
diff --git a/web/src/stream_list.ts b/web/src/stream_list.ts
index e04deced4e..5c97259521 100644
--- a/web/src/stream_list.ts
+++ b/web/src/stream_list.ts
@@ -664,11 +664,11 @@ export function refresh_muted_or_unmuted_stream(sub: StreamSubscription): void {
 }
 
 export function get_sidebar_stream_topic_info(filter: Filter): {
-    stream_id?: number;
+    stream_id: number | undefined;
     topic_selected: boolean;
 } {
     const result: {
-        stream_id?: number;
+        stream_id: number | undefined;
         topic_selected: boolean;
     } = {
         stream_id: undefined,
diff --git a/web/src/topic_list.ts b/web/src/topic_list.ts
index ded244b774..53c83506be 100644
--- a/web/src/topic_list.ts
+++ b/web/src/topic_list.ts
@@ -141,7 +141,7 @@ export function spinner_li(): ListInfoNode {
 }
 
 export class TopicListWidget {
-    prior_dom?: vdom.Tag<ListInfoNodeOptions> = undefined;
+    prior_dom: vdom.Tag<ListInfoNodeOptions> | undefined = undefined;
     $parent_elem: JQuery;
     my_stream_id: number;
 
diff --git a/web/src/typeahead_helper.ts b/web/src/typeahead_helper.ts
index 5206f8bcd8..5c18d45f7f 100644
--- a/web/src/typeahead_helper.ts
+++ b/web/src/typeahead_helper.ts
@@ -97,12 +97,12 @@ type StreamData = {
 };
 
 export function render_typeahead_item(args: {
-    primary?: string;
+    primary?: string | undefined;
     is_person?: boolean;
     img_src?: string;
-    status_emoji_info?: UserStatusEmojiInfo;
+    status_emoji_info?: UserStatusEmojiInfo | undefined;
     secondary?: string | null;
-    pronouns?: string;
+    pronouns?: string | undefined;
     is_user_group?: boolean;
     stream?: StreamData;
     is_unsubscribed?: boolean;
@@ -443,10 +443,10 @@ export function sort_recipients<UserType extends UserOrMentionPillData | UserPil
 }: {
     users: UserType[];
     query: string;
-    current_stream_id?: number;
-    current_topic?: string;
+    current_stream_id?: number | undefined;
+    current_topic?: string | undefined;
     groups?: UserGroupPillData[];
-    max_num_items?: number;
+    max_num_items?: number | undefined;
 }): (UserType | UserGroupPillData)[] {
     function sort_relevance(items: UserType[]): UserType[] {
         return sort_people_for_relevance(items, current_stream_id, current_topic);
diff --git a/web/src/util.ts b/web/src/util.ts
index 1e2f268bfb..044e3d10f9 100644
--- a/web/src/util.ts
+++ b/web/src/util.ts
@@ -74,7 +74,7 @@ export function extract_pm_recipients(recipients: string): string[] {
 // When the type is "private", properties from to_user_ids might be undefined.
 // See https://github.com/zulip/zulip/pull/23032#discussion_r1038480596.
 export type Recipient =
-    | {type: "private"; to_user_ids?: string; reply_to: string}
+    | {type: "private"; to_user_ids?: string | undefined; reply_to: string}
     | ({type: "stream"} & StreamTopic);
 
 export const same_recipient = function util_same_recipient(a?: Recipient, b?: Recipient): boolean {
diff --git a/web/src/widgetize.ts b/web/src/widgetize.ts
index 0a72602c9f..ff8dfea211 100644
--- a/web/src/widgetize.ts
+++ b/web/src/widgetize.ts
@@ -14,8 +14,8 @@ type ZFormExtraData = {
 
 // TODO: This TodoWidgetExtraData type should be moved to web/src/todo_widget.js when it will be migrated
 type TodoWidgetExtraData = {
-    task_list_title?: string;
-    tasks?: {task: string; desc: string}[];
+    task_list_title?: string | undefined;
+    tasks?: {task: string; desc: string}[] | undefined;
 };
 
 type WidgetExtraData = PollWidgetExtraData | TodoWidgetExtraData | ZFormExtraData | null;