remotion-dev/remotion · error · TypeError

type of endAt prop must be a number, instead got type ${type

Error message

type of endAt prop must be a number, instead got type ${typeof endAt}.

What it means

The deprecated `endAt` prop on media components specifies the frame at which playback should stop, and it must be a number. validateStartFromProps checks the runtime type because values destructured from props, configs, or JSON may arrive as strings rather than numbers.

Source

Thrown at packages/core/src/validate-start-from-props.ts:25

			throw new TypeError(
				`type of startFrom prop must be a number, instead got type ${typeof startFrom}.`,
			);
		}

		if (isNaN(startFrom) || startFrom === Infinity) {
			throw new TypeError('startFrom prop can not be NaN or Infinity.');
		}

		if (startFrom < 0) {
			throw new TypeError(
				`startFrom must be greater than equal to 0 instead got ${startFrom}.`,
			);
		}
	}

	if (typeof endAt !== 'undefined') {
		if (typeof endAt !== 'number') {
			throw new TypeError(
				`type of endAt prop must be a number, instead got type ${typeof endAt}.`,
			);
		}

		if (isNaN(endAt)) {
			throw new TypeError('endAt prop can not be NaN.');
		}

		if (endAt <= 0) {
			throw new TypeError(
				`endAt must be a positive number, instead got ${endAt}.`,
			);
		}
	}

	if ((endAt as number) < (startFrom as number)) {
		throw new TypeError('endAt prop must be greater than startFrom prop.');
	}

View on GitHub (pinned to 78fe4bb3fd)

Solutions

Pass endAt as a numeric literal: endAt={200}.
If the value is a string, parse it: endAt={Number(myStr)} after a finiteness check.
Migrate to the non-deprecated `trimAfter` prop, which has the same semantics.
Omit the prop if you do not need to cap the end.

Example fix

// before
<Audio src={src} endAt="180" />
// after
<Audio src={src} trimAfter={180} />

Defensive patterns

Strategy: type-guard

Validate before calling

if (endAt !== undefined && typeof endAt !== 'number') {
  throw new Error('endAt must be a number or undefined');
}

Type guard

const isEndAt = (v: unknown): v is number | undefined =>
  v === undefined || typeof v === 'number';

Prevention

Migrate from endAt to the non-deprecated trimAfter to avoid future removal.
Parse string sources with Number() and validate before passing.
Type scene/config descriptors so numbers are not serialized as strings.

When it happens

Trigger: Passing endAt as a string (endAt="200"), an object, or any non-number non-undefined value to a media component.

Common situations: Reading endAt from a JSON scene descriptor or CMS where numbers are serialized as strings; passing a value from URL query params without conversion.

Related errors

AI-assisted analysis of remotion-dev/remotion@78fe4bb3fd (2026-08-12). Data as JSON: /api/errors/652e7621f6531f2a. Report an issue: GitHub.