withastro/astro · error

Astro expected an SVG for "${transform.src}" but the source

Error message

Astro expected an SVG for "${transform.src}" but the source is ${bufferFormat}. Passing it through as ${bufferFormat} instead.

What it means

In the Sharp image service, transform() was asked to process an image whose declared/configured format is SVG, but format detection on the actual input buffer identified it as a different format (bufferFormat). Instead of failing, Sharp passes the buffer through unoptimized in its detected format and logs this warning, so the build does not break on a mismatched extension or mislabeled src.

Source

Thrown at packages/astro/src/assets/services/sharp.ts:161

	validateOptions: baseService.validateOptions,
	getURL: baseService.getURL,
	parseURL: baseService.parseURL,
	getHTMLAttributes: baseService.getHTMLAttributes,
	getSrcSet: baseService.getSrcSet,
	getRemoteSize: baseService.getRemoteSize,
	async transform(inputBuffer, transformOptions, config, logger) {
		if (!sharp) sharp = await loadSharp();
		const transform: BaseServiceTransform = transformOptions as BaseServiceTransform;
		const kernel = config.service.config.kernel;

		const bufferFormat = detector(inputBuffer);
		// Resolve the output format from the buffer when validateOptions deferred (ambiguous remote URL hit SSR, manually formed URLs etc)
		const outputFormat = transform.format ?? resolveDefaultOutputFormat(bufferFormat);

		// TODO: Sharp has some support for SVGs, we could probably support this once Sharp is the default and only service.
		if (outputFormat === 'svg') {
			if (bufferFormat && bufferFormat !== 'svg') {
				logger.warn(
					`Astro expected an SVG for "${transform.src}" but the source is ${bufferFormat}. Passing it through as ${bufferFormat} instead.`,
				);
				return { data: inputBuffer, format: bufferFormat as ImageOutputFormat };
			}
			return { data: inputBuffer, format: 'svg' };
		}

		// If we couldn't figure out the format, it's probably something weird we shouldn't try to process.
		if (!bufferFormat) {
			throw new AstroError({
				...AstroErrorData.NoImageMetadata,
				message: AstroErrorData.NoImageMetadata.message(transform.src),
			});
		}

		if (bufferFormat === 'svg' && !config.dangerouslyProcessSVG) {
			throw new AstroError({
				...AstroErrorData.UnsupportedImageFormat,

View on GitHub (pinned to e294953aa8)

Solutions

1. Verify the source file truly is an SVG — its extension or config entry may mislabel a JPEG/PNG as .svg
2. If the file is intentionally another format, update its extension or the image's format option to match
3. Rename or fix the file so the declared format matches the actual encoded format

When it happens

Trigger: Thrown at packages/astro/src/assets/services/sharp.ts:161 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of withastro/astro@e294953aa8 (2026-09-09). Data as JSON: /api/errors/f0331c206f303b2d. Report an issue: GitHub.