diff --git a/packages/backend/assets/embed.js b/packages/backend/assets/embed.js
new file mode 100644
index 0000000000..24fccc1b6c
--- /dev/null
+++ b/packages/backend/assets/embed.js
@@ -0,0 +1,31 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: MIT
+ */
+//@ts-check
+(() => {
+	/** @type {NodeListOf<HTMLIFrameElement>} */
+	const els = document.querySelectorAll('iframe[data-misskey-embed-id]');
+
+	window.addEventListener('message', function (event) {
+		els.forEach((el) => {
+			if (event.source !== el.contentWindow) {
+				return;
+			}
+
+			const id = el.dataset.misskeyEmbedId;
+
+			if (event.data.type === 'misskey:embed:ready') {
+				el.contentWindow?.postMessage({
+					type: 'misskey:embedParent:registerIframeId',
+					payload: {
+						iframeId: id,
+					}
+				}, '*');
+			}
+			if (event.data.type === 'misskey:embed:changeHeight' && event.data.iframeId === id) {
+				el.style.height = event.data.payload.height + 'px';
+			}
+		});
+	});
+})();
diff --git a/packages/backend/src/server/web/ClientServerService.ts b/packages/backend/src/server/web/ClientServerService.ts
index 86888f45c1..d5b2096f87 100644
--- a/packages/backend/src/server/web/ClientServerService.ts
+++ b/packages/backend/src/server/web/ClientServerService.ts
@@ -425,6 +425,13 @@ export class ClientServerService {
 		// Manifest
 		fastify.get('/manifest.json', async (request, reply) => await this.manifestHandler(reply));
 
+		// Embed Javascript
+		fastify.get('/embed.js', async (request, reply) => {
+			return await reply.sendFile('/embed.js', staticAssets, {
+				maxAge: ms('1 day'),
+			});
+		});
+
 		fastify.get('/robots.txt', async (request, reply) => {
 			return await reply.sendFile('/robots.txt', staticAssets);
 		});
diff --git a/packages/frontend/vite.config.local-dev.ts b/packages/frontend/vite.config.local-dev.ts
index f9dff13b15..9ee44a7cad 100644
--- a/packages/frontend/vite.config.local-dev.ts
+++ b/packages/frontend/vite.config.local-dev.ts
@@ -40,6 +40,8 @@ const devConfig = {
 				ws: true,
 			},
 			'/favicon.ico': httpUrl,
+			'/robots.txt': httpUrl,
+			'/embed.js': httpUrl,
 			'/identicon': {
 				target: httpUrl,
 				rewrite(path) {