remotion-dev/remotion · error · Error

${path} must be an object.

Error message

${path} must be an object.

What it means

Each element of the top-level JSON array must be a Caption object. This error is thrown when an element is a non-object value (string, number, boolean, null, or a nested array). isObject explicitly rejects arrays and null.

Source

Thrown at packages/studio/src/components/parse-caption-file.ts:39

	let parsed: unknown;
	try {
		parsed = JSON.parse(contents);
	} catch (error) {
		throw new Error(
			`Invalid JSON: ${error instanceof Error ? error.message : String(error)}`,
		);
	}

	if (!Array.isArray(parsed)) {
		throw new Error('Expected a Remotion Caption[] JSON array.');
	}

	let previousStart: number | null = null;
	for (const [index, caption] of parsed.entries()) {
		const path = `captions[${index}]`;
		if (!isObject(caption)) {
			throw new Error(`${path} must be an object.`);
		}

		if (typeof caption.text !== 'string') {
			throw new Error(`${path}.text must be a string.`);
		}

		if (!isFiniteNumber(caption.startMs) || caption.startMs < 0) {
			throw new Error(`${path}.startMs must be a finite, non-negative number.`);
		}

		if (!isFiniteNumber(caption.endMs) || caption.endMs < 0) {
			throw new Error(`${path}.endMs must be a finite, non-negative number.`);
		}

		if (caption.endMs < caption.startMs) {
			throw new Error(`${path}.endMs must not be earlier than startMs.`);
		}

View on GitHub (pinned to b2f4e34732)

Solutions

1. Inspect element captions[i] in the JSON and replace it with a full caption object ({text, startMs, endMs, ...})
2. Re-export the caption file from the original tool in Remotion Caption JSON format
3. Validate each array element is an object before passing the file to the studio

Example fix

// before
["hello world"]
// after
[{"text": "hello world", "startMs": 0, "endMs": 2000, "timestampMs": null, "confidence": null}]

const arr: unknown[] = JSON.parse(contents);
arr.forEach((el, i) => {
  if (typeof el !== 'object' || el === null || Array.isArray(el)) {
    throw new Error(`captions[${i}] must be an object`);
  }
});

const isCaptionObject = (v: unknown): v is Record<string, unknown> =>
  typeof v === 'object' && v !== null && !Array.isArray(v);

try {
  const captions = parseCaptionFile({fileName, contents});
} catch (e) {
  // message names captions[i]; fix that element and retry
  console.error((e as Error).message);
}

When it happens

Trigger: parseCaptionFile receives contents whose parsed array contains an element like "hello", 42, null, true, or [] at captions[i].

Common situations: A malformed export that flattens captions into mixed values; copy/paste corruption inserting a stray value between objects; manually writing ["line one", "line two"] instead of objects.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• Expected a Remotion Caption[] JSON array.
• ${path}.text must be a string.
• ${path}.startMs must be a finite, non-negative number.
• ${path}.endMs must be a finite, non-negative number.
• ${path}.endMs must not be earlier than startMs.

AI-assisted analysis of remotion-dev/remotion@b2f4e34732 (2026-09-09). Data as JSON: /api/errors/cfe86c32a07e06dd. Report an issue: GitHub.