withastro/astro · error · AstroError

FileGlobNotSupported

FileGlobNotSupported

Error message

Glob patterns are not supported in the `file` loader. Use the `glob` loader instead.

What it means

The `file()` content loader reads exactly one file (JSON, YAML, TOML, or custom-parsed). Passing a filename containing `*` means you are describing multiple files, which file() cannot do, so it throws FileGlobNotSupported at config-load time and points you to the `glob()` loader.

Solutions

Switch to the glob loader: `glob({ pattern: '**/*.json', base: './src/content/blog' })`.
Or point file() at one concrete file: `file('src/content/blog/posts.json')`.

Example fix

// before
const Blog = defineCollection({ loader: file('src/content/blog/*.json') });

// after
import { glob } from 'astro/loaders';
const Blog = defineCollection({
  loader: glob({ pattern: '**/*.json', base: './src/content/blog' }),
});

Defensive patterns

Strategy: validation

Validate before calling

import { file, glob } from 'astro/loaders';

const patternLike = (name: string) => name.includes('*');
const loader = patternLike('src/content/blog/*.json')
  ? glob({ pattern: 'blog/**/*.json' })
  : file('src/content/blog.json');

Type guard

const isSingleFileName = (name: string): boolean => !name.includes('*');

Prevention

Remember file() = exactly one file; glob() = many files.
Keep loader choice in one place per collection so switching is a one-line change.

When it happens

Trigger: `defineCollection({ loader: file('src/content/blog/*.json') })` or any fileName argument containing a `*` character.

Common situations: Migrating from the legacy content collections API or from a glob loader and mixing up the two; wanting 'all JSON files in a directory' and reaching for file() out of habit.

Related errors

AI-assisted analysis of withastro/astro@52e6c34790 (2026-08-18). Data as JSON: /api/errors/2428c30903e86dfb. Report an issue: GitHub.

Appendix: source

Thrown at packages/astro/src/content/loaders/file.ts:31

type ParserOutput = Record<string, Record<string, unknown>> | Array<Record<string, unknown>>;

interface FileOptions {
	/**
	 * the parsing function to use for this data
	 * @default JSON.parse or yaml.load, depending on the extension of the file
	 * */
	parser?: (text: string) => Promise<ParserOutput> | ParserOutput;
}

/**
 * Loads entries from a JSON file. The file must contain an array of objects that contain unique `id` fields, or an object with string keys.
 * @param fileName The path to the JSON file to load, relative to the content directory.
 * @param options Additional options for the file loader
 */
export function file(fileName: string, options?: FileOptions): Loader {
	if (fileName.includes('*')) {
		throw new AstroError(FileGlobNotSupported);
	}

	let parse: ((text: string) => any) | null = null;

	const ext = fileName.split('.').at(-1);
	if (ext === 'json') {
		parse = JSON.parse;
	} else if (ext === 'yml' || ext === 'yaml') {
		parse = (text) =>
			yaml.load(text, {
				filename: fileName,
			});
	} else if (ext === 'toml') {
		parse = toml.parse;
	}
	if (options?.parser) parse = options.parser;

	if (parse === null) {

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