remotion-dev/remotion · error · TypeError

"codec" must be a string

Error message

"codec" must be a string 

What it means

First guard in validateLambdaCodec: the codec argument must be a string. Any non-string (undefined, null, number, object) throws a TypeError. (Note: the message has a trailing space, which is a minor source artifact.) The codec is validated against the serverlessCodecs allowlist only after this passes.

Source

Thrown at packages/lambda-client/src/validate-lambda-codec.ts:7

/* eslint-disable no-console */
import type {ServerlessCodec} from '@remotion/serverless-client';
import {serverlessCodecs} from '@remotion/serverless-client';

export const validateLambdaCodec = (codec: unknown): ServerlessCodec => {
	if (typeof codec !== 'string') {
		throw new TypeError('"codec" must be a string ');
	}

	if (!(serverlessCodecs as readonly string[]).includes(codec)) {
		throw new TypeError(
			"'" +
				codec +
				"' is not a valid codec for Lambda. The following values are supported: " +
				serverlessCodecs.join(', '),
		);
	}

	if ((codec as string) === 'h264-mkv') {
		console.warn(
			'The "h264-mkv" codec for renderMediaOnLambda() is deprecated - it\'s now just "h264".',
		);

		return 'h264';
	}

View on GitHub (pinned to 78fe4bb3fd)

Solutions

1. Pass a string codec such as 'h264', 'h265', 'vp8', 'vp9', 'mp3', 'aac', 'wav', or 'gif' (see serverlessCodecs).
2. Provide a sensible default (e.g., 'h264') when codec is not configured.
3. Type your options object so codec is required string to catch this at compile time.

Example fix

// before
renderMediaOnLambda({ composition: 'Main', codec: undefined });

// after
renderMediaOnLambda({ composition: 'Main', codec: 'h264' });

if (typeof codec !== 'string') {
  throw new TypeError(`codec must be a string, got ${typeof codec}`);
}
validateLambdaCodec(codec);

const isString = (v: unknown): v is string => typeof v === 'string';

When it happens

Trigger: Calling renderMediaOnLambda/renderStillOnLambda or any path that runs validateLambdaCodec with a non-string codec value (e.g., undefined from a missing config field, a number, or an object).

Common situations: Codec option defaulted to undefined; reading codec from config where the field is missing; passing a codec constant that resolved to undefined after a refactor; spread of an options object without codec.

Related errors

• parameter 'diskSizeInMb' must be a number, got a ${typeof di
• parameter 'memorySizeInMb' must be a number, got a ${typeof
• "codec" must be a string
• No supported configs
• ${region} is not a supported AWS region. Must be one of: ${A

AI-assisted analysis of remotion-dev/remotion@78fe4bb3fd (2026-08-12). Data as JSON: /api/errors/96ebd7df0dbe0cd4. Report an issue: GitHub.