remotion-dev/remotion · error · Error

Detected Vite pre-bundling, which will break the worker. Ple

Error message

Detected Vite pre-bundling, which will break the worker.
Please add the following to your vite.config.js:
  optimizeDeps: {
    exclude: ["@remotion/media-parser/worker"]
  }

What it means

Thrown by parseMediaOnWebWorker when import.meta.url contains '.vite/deps', indicating Vite pre-bundled the worker entry. Vite's dependency pre-bundling breaks worker instantiation because it rewrites module URLs and the new URL('./worker-web-entry.mjs', import.meta.url) pattern no longer resolves to a servable worker script.

Source

Thrown at packages/media-parser/src/worker.module.ts:34

	F extends Options<ParseMediaFields>,
>(
	params: ParseMediaOnWorkerOptions<F>,
) => {
	if (typeof Worker === 'undefined') {
		throw new Error(
			'"Worker" is not available. Cannot call parseMediaOnWebWorker()',
		);
	}

	if (import.meta.url.includes('.vite/deps')) {
		const err = [
			'Detected Vite pre-bundling, which will break the worker.',
			'Please add the following to your vite.config.js:',
			'  optimizeDeps: {',
			'    exclude: ["@remotion/media-parser/worker"]',
			'  }',
		].join('\n');
		throw new Error(err);
	}

	const worker = new Worker(new URL('./worker-web-entry.mjs', import.meta.url));

	return parseMediaOnWorkerImplementation(
		params,
		worker,
		'parseMediaOnWebWorker',
	);
};

View on GitHub (pinned to 78fe4bb3fd)

Solutions

1. Add optimizeDeps.exclude: ['@remotion/media-parser/worker'] to vite.config as the error message instructs.
2. If the error persists, also exclude the package from build.rollupOptions or use the in-process parseMedia instead.
3. Restart the Vite dev server after editing vite.config so optimizeDeps cache is rebuilt.

Example fix

// before - vite.config.js
export default { plugins: [react()] };

// after
export default {
  plugins: [react()],
  optimizeDeps: { exclude: ['@remotion/media-parser/worker'] },
};

// vite.config.js
export default {
  optimizeDeps: { exclude: ['@remotion/media-parser/worker'] },
};

try { await parseMediaOnWebWorker(opts); } catch (e) { if (/Vite pre-bundling/.test(String((e as Error).message))) { console.error('Add optimizeDeps.exclude for @remotion/media-parser/worker, then restart Vite'); } throw e; }

When it happens

Trigger: Using parseMediaOnWebWorker inside a Vite-powered app (Vite dev server or build) without excluding @remotion/media-parser/worker from optimizeDeps. Vite pre-bundles the package, the worker URL is rewritten, and the guard trips to fail fast rather than producing a broken worker.

Common situations: New Vite project importing the media-parser web worker. Upgrading Vite and hitting stricter pre-bundling. Copying a snippet from a non-Vite project into a Vite app without adjusting the config.

Related errors

• The public directory was specified as "${p}", which is the r
• The public directory was specified as "${p}", and while this
• The public directory was specified as "${p}", but this folde
• `reader` should not be provided to `${apiName}`. If you want
• "Worker" is not available. Cannot call parseMediaOnServerWor

AI-assisted analysis of remotion-dev/remotion@78fe4bb3fd (2026-08-12). Data as JSON: /api/errors/473561528c2dff32. Report an issue: GitHub.