diff --git a/web/src/rendered_markdown.ts b/web/src/rendered_markdown.ts
index e45d73ab8c..a96e0c1e8a 100644
--- a/web/src/rendered_markdown.ts
+++ b/web/src/rendered_markdown.ts
@@ -16,6 +16,7 @@ import * as realm_playground from "./realm_playground";
 import * as rows from "./rows";
 import * as rtl from "./rtl";
 import * as sub_store from "./sub_store";
+import * as thumbnail from "./thumbnail";
 import * as timerender from "./timerender";
 import * as user_groups from "./user_groups";
 import {user_settings} from "./user_settings";
@@ -337,4 +338,18 @@ export const update_elements = ($content: JQuery): void => {
             .contents()
             .unwrap();
     }
+
+    $content
+        .find('div.message_inline_image > a > img[src^="/user_uploads/thumbnail/"]')
+        .each(function (): void {
+            const $inline_img_thumbnail = $(this);
+            let thumbnail_name = thumbnail.preferred_format.name;
+            if ($inline_img_thumbnail.attr("data-animated") === "true") {
+                thumbnail_name = thumbnail.animated_format.name;
+            }
+            $inline_img_thumbnail.attr(
+                "src",
+                $inline_img_thumbnail.attr("src")!.replace(/\/[^/]+$/, "/" + thumbnail_name),
+            );
+        });
 };
diff --git a/web/tests/rendered_markdown.test.js b/web/tests/rendered_markdown.test.js
index 46203330c0..7e04a35f1c 100644
--- a/web/tests/rendered_markdown.test.js
+++ b/web/tests/rendered_markdown.test.js
@@ -23,6 +23,7 @@ mock_cjs("clipboard", Clipboard);
 
 const realm_playground = mock_esm("../src/realm_playground");
 const copied_tooltip = mock_esm("../src/copied_tooltip");
+const thumbnail = mock_esm("../src/thumbnail");
 user_settings.emojiset = "apple";
 
 const rm = zrequire("rendered_markdown");
@@ -138,6 +139,15 @@ const get_content_element = () => {
     $content.set_find_results("div.spoiler-header", $array([]));
     $content.set_find_results("div.codehilite", $array([]));
     $content.set_find_results(".message_inline_video video", $array([]));
+    $content.set_find_results(
+        'div.message_inline_image > a > img[src^="/user_uploads/thumbnail/"]',
+        $array([]),
+    );
+    $content.set_find_results(
+        "div.message_inline_image img, div.message_inline_image video",
+        $array([]),
+    );
+
     set_message_for_message_content($content, undefined);
 
     // Fend off dumb security bugs by forcing devs to be
@@ -191,6 +201,67 @@ run_test("message_inline_video", () => {
     window.GestureEvent = false;
 });
 
+run_test("message_inline_animated_image", ({override}) => {
+    const $content = get_content_element();
+    const $elem = $.create("img");
+
+    $elem.attr("data-animated", "false");
+    $elem.attr("src", "/path/to/image.png");
+
+    $content.set_find_results(
+        'div.message_inline_image > a > img[src^="/user_uploads/thumbnail/"]',
+        $array([$elem]),
+    );
+
+    const thumbnail_formats = [
+        {
+            name: "840x560-anim.webp",
+            max_width: 840,
+            max_height: 560,
+            format: "webp",
+            animated: true,
+        },
+        {
+            name: "840x560.webp",
+            max_width: 840,
+            max_height: 560,
+            format: "webp",
+            animated: false,
+        },
+        {
+            name: "300x200-anim.webp",
+            max_width: 300,
+            max_height: 200,
+            format: "webp",
+            animated: true,
+        },
+        {
+            name: "300x200.webp",
+            max_width: 300,
+            max_height: 200,
+            format: "webp",
+            animated: false,
+        },
+        {
+            name: "300x200.jpg",
+            max_width: 300,
+            max_height: 200,
+            format: "jpg",
+            animated: false,
+        },
+    ];
+    // TODO: Initialize the real thumbnail.ts rather than mocking it.
+    override(thumbnail, "preferred_format", thumbnail_formats[1]);
+    override(thumbnail, "animated_format", thumbnail_formats[0]);
+
+    rm.update_elements($content);
+    assert.equal($elem.attr("src"), "/path/to/840x560.webp");
+
+    $elem.attr("data-animated", "true");
+    rm.update_elements($content);
+    assert.equal($elem.attr("src"), "/path/to/840x560-anim.webp");
+});
+
 run_test("user-mention", () => {
     // Setup
     const $content = get_content_element();