remotion-dev/remotion · error · TypeError

outputs.${layer}.outputTarget must be arraybuffer or web-fs.

Error message

outputs.${layer}.outputTarget must be arraybuffer or web-fs.

What it means

Each layer output's outputTarget field, if present, must be exactly 'arraybuffer' or 'web-fs'. Any other value (including other string targets or wrong types) is rejected with this TypeError so the library only commits to output sinks it supports.

Source

Thrown at packages/video-matting/src/separate-video-layers.ts:123

	output,
}: {
	layer: 'base' | 'foreground';
	output: VideoLayerOutputOptions | undefined;
}) => {
	if (output === undefined) {
		return;
	}

	if (!output || typeof output !== 'object' || Array.isArray(output)) {
		throw new TypeError(`outputs.${layer} must be an object.`);
	}

	if (
		output.outputTarget !== undefined &&
		output.outputTarget !== 'arraybuffer' &&
		output.outputTarget !== 'web-fs'
	) {
		throw new TypeError(
			`outputs.${layer}.outputTarget must be arraybuffer or web-fs.`,
		);
	}

	if (
		output.outputTarget !== undefined &&
		output.outputWritable !== undefined
	) {
		throw new TypeError(
			`outputs.${layer} cannot specify both outputTarget and outputWritable.`,
		);
	}

	if (output.outputWritable !== undefined) {
		if (
			typeof WritableStream === 'undefined' ||
			!(output.outputWritable instanceof WritableStream)
		) {

View on GitHub (pinned to b2f4e34732)

Solutions

1. Set outputTarget to 'arraybuffer' to receive an ArrayBuffer result.
2. Set outputTarget to 'web-fs' to write via the File System Access API.
3. Fix casing/typos ('arraybuffer' is all-lowercase).
4. Use outputWritable instead if you want to pipe into your own sink.

Example fix

// before
outputs: {video: {outputTarget: 'file'}}
// after
outputs: {video: {outputTarget: 'arraybuffer'}}

const VALID = ['arraybuffer', 'web-fs'] as const;
if (out.outputTarget !== undefined && !VALID.includes(out.outputTarget)) throw new TypeError('bad outputTarget');

const isOutputTarget = (v: unknown): v is 'arraybuffer' | 'web-fs' => v === 'arraybuffer' || v === 'web-fs';

try { await separateVideoLayers(opts); } catch (e) { if (e instanceof TypeError && e.message.includes('outputTarget')) { console.error('outputTarget must be arraybuffer or web-fs'); } throw e; }

When it happens

Trigger: Passing {outputTarget: 'file'}, {outputTarget: 'blob'}, {outputTarget: 'stream'}, or a non-string value in a layer's output config.

Common situations: Copy-pasting target names from another library's API; assuming Node-style 'file' targets work in the browser build; typos like 'arrayBuffer' (wrong case).

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• "${name}" must be ${formatEnum(variants)}, but got ${JSON.st
• "direction" must be ${formatEnum(WAVE_DIRECTIONS)}, but got
• "${name}" must be one of ${variants.join(', ')}
• Value for ${JSON.stringify(key)} must be one of ${Object.key
• Argument missing for parameter "frame"

AI-assisted analysis of remotion-dev/remotion@b2f4e34732 (2026-09-09). Data as JSON: /api/errors/c85dc187e7aa449f. Report an issue: GitHub.