diff --git a/src/markdown.ts b/src/markdown.ts
index c582277b8..4325104db 100644
--- a/src/markdown.ts
+++ b/src/markdown.ts
@@ -316,22 +316,32 @@ function renderIntoPieces(renderer: Renderer, root: string, sourcePath: string):
     }
     let result = "";
     for (const piece of context.pieces) {
-      result += piece.html = normalizePieceHtml(piece.html, root, sourcePath, context);
+      result += piece.html = normalizePieceHtml(piece.html, sourcePath, context);
     }
     return result;
   };
 }
 
-function normalizePieceHtml(html: string, root: string, sourcePath: string, context: ParseContext): string {
+const SUPPORTED_PROPERTIES: readonly {query: string; src: string}[] = Object.freeze([
+  {query: "img[src]", src: "src"},
+  {query: "video[src]", src: "src"},
+  {query: "video source[src]", src: "src"},
+  {query: "audio[src]", src: "src"},
+  {query: "audio source[src]", src: "src"},
+  {query: "link[href]", src: "href"}
+]);
+export function normalizePieceHtml(html: string, sourcePath: string, context: ParseContext): string {
   const {document} = parseHTML(html);
 
   // Extracting references to files (such as from linked stylesheets).
-  for (const element of document.querySelectorAll("link[href]") as any as Iterable<Element>) {
-    const href = element.getAttribute("href")!;
-    const path = getLocalPath(sourcePath, href);
-    if (path) {
-      context.files.push(fileReference(href, sourcePath));
-      element.setAttribute("href", relativeUrl(sourcePath, join("_file", path)));
+  for (const {query, src} of SUPPORTED_PROPERTIES) {
+    for (const element of document.querySelectorAll(query) as any as Iterable<Element>) {
+      const relativePath = element.getAttribute(src)!;
+      const path = getLocalPath(sourcePath, relativePath);
+      if (path) {
+        context.files.push(fileReference(relativePath, sourcePath));
+        element.setAttribute(src!, relativeUrl(sourcePath, join("_file", path)));
+      }
     }
   }
 
diff --git a/test/promote-file-attachment-test.ts b/test/promote-file-attachment-test.ts
new file mode 100644
index 000000000..d83ae5d02
--- /dev/null
+++ b/test/promote-file-attachment-test.ts
@@ -0,0 +1,79 @@
+import assert from "node:assert";
+import {normalizePieceHtml} from "../src/markdown.js";
+import {resolvePath} from "../src/url.js";
+
+const html = (strings, ...values) => String.raw({raw: strings}, ...values);
+const mockContext = () => ({files: [], imports: [], pieces: [], startLine: 0, currentLine: 0});
+
+describe("file attachments", () => {
+  describe("success", () => {
+    const sourcePath = "/attachments.md";
+
+    it("img[src]", () => {
+      const htmlStr = html`<img src="./test.png">`;
+      const expected = html`<img src="./_file/test.png">`;
+      const context = mockContext();
+      const actual = normalizePieceHtml(htmlStr, sourcePath, context);
+
+      assert.equal(expected, actual);
+      assert.deepEqual(context.files, [
+        {
+          mimeType: "image/png",
+          name: "./test.png",
+          path: "./_file/test.png"
+        }
+      ]);
+    });
+
+    it("video[src]", () => {
+      const htmlStr = html`<video src="observable.mov" controls>
+      Learn more about Observable CLI
+      </video>`;
+      const expected = html`<video src="./_file/observable.mov" controls>
+      Learn more about Observable CLI
+      </video>`;
+      const context = mockContext();
+      const actual = normalizePieceHtml(htmlStr, sourcePath, context);
+
+      assert.equal(expected, actual);
+      assert.deepEqual(context.files, [
+        {
+          mimeType: "video/quicktime",
+          name: "observable.mov",
+          path: "./_file/observable.mov"
+        }
+      ]);
+    });
+
+    it("video source[src]", () => {
+      const htmlStr = html`<video width="320" height="240" controls>
+      <source src="observable.mp4" type="video/mp4">
+      <source src="observable.mov" type="video/mov">
+      Learn more about Observable CLI
+      </video>`;
+
+      const expected = html`<video width="320" height="240" controls>
+      <source src="./_file/observable.mp4" type="video/mp4">
+      <source src="./_file/observable.mov" type="video/mov">
+      Learn more about Observable CLI
+      </video>`;
+
+      const context = mockContext();
+      const actual = normalizePieceHtml(htmlStr, sourcePath, context);
+
+      assert.equal(expected, actual);
+      assert.deepEqual(context.files, [
+        {
+          mimeType: "video/mp4",
+          name: "observable.mp4",
+          path: "./_file/observable.mp4"
+        },
+        {
+          mimeType: "video/quicktime",
+          name: "observable.mov",
+          path: "./_file/observable.mov"
+        }
+      ]);
+    });
+  });
+});