require-frontmatter-fields.md

require-frontmatter-fields

📝 Require configured YAML frontmatter fields.

🚫 This rule is disabled in the following configs: ✅ recommended, ☑️ unopinionated.

Require specified keys in a top-level YAML mapping. This is useful for Markdown collections such as blog posts or documentation pages that require consistent metadata.

The rule only checks YAML frontmatter that @eslint/markdown has parsed. Configure the Markdown language and enable YAML frontmatter:

import markdown from '@eslint/markdown';
import unicorn from 'eslint-plugin-unicorn';
import {defineConfig} from 'eslint/config';

export default defineConfig([
	{
		files: ['**/*.md'],
		plugins: {
			markdown,
			unicorn,
		},
		language: 'markdown/gfm',
		languageOptions: {
			frontmatter: 'yaml',
		},
		rules: {
			'unicorn/require-frontmatter-fields': [
				'error',
				{
					fields: [
						'title',
						'description',
						'date',
					],
				},
			],
		},
	},
]);

Examples

YAML frontmatter contents:

# ❌
title: Hello

# ✅
title: Hello
description: A description
date: 2026-07-10

Options

fields

Type: string[]
Default: []

The required keys in a top-level YAML mapping. The rule does not require frontmatter itself, so Markdown files without YAML frontmatter are ignored.

Malformed YAML frontmatter is ignored. This rule checks only field presence. It does not validate field values, nested fields, field order, TOML frontmatter, or JSON frontmatter.