Markdown & MDX Formatting & Linting

Format and lint markdown and MDX files using markdownlint CLI tools with comprehensive understanding of all markdown rules.

Quick Start

# Check if markdownlint is available
which markdownlint || which markdownlint

# Install if needed
pnpm add -D markdownlint
# or
npm install -g markdownlint

# Auto-fix files (markdown and MDX)
markdownlint --fix "**/*.{md,mdx}"

# Check specific files
markdownlint README.md docs/**/*.md content/**/*.mdx

Configuration Detection

Check for config files in this order:

1. .markdownlint.json
2. .markdownlint.jsonc
3. .markdownlint.yaml
4. .markdownlintrc
5. markdownlint key in package.json

Common Workflow

1. Detect environment: Check for markdownlint CLI
2. Find config: Look for config files
3. Run linter: Identify issues
4. Apply fixes: Auto-fix or manual
5. Verify: Re-run to confirm

Most Common Issues & Quick Fixes

Headings

• MD001: Heading levels increment (# → ## → ### not # → ###)
• MD018/MD019: Single space after hash (# Heading not #Heading)
• MD022: Blank lines around headings
• MD025: Single H1 per document
• MD041: First line should be H1

<!-- Good heading structure -->
# Main Title

## Section

### Subsection

Content here...

Lists

• MD004: Consistent list markers (all - or all *)
• MD007: Nested lists indent 2 spaces
• MD030: Single space after list marker
• MD032: Blank lines around lists

<!-- Good list structure -->
- Item 1
  - Nested item
  - Another nested
- Item 2

Whitespace

• MD009: No trailing spaces
• MD010: Use spaces not tabs
• MD012: Single blank lines (not multiple)
• MD047: File ends with newline

Links & Images

• MD034: Wrap bare URLs in <>: <http://example.com>
• MD042: Links need text: [Link Text](url) not [](url)
• MD045: Images need alt text: ![Description](image.png)

Code Blocks

• MD031: Blank lines around code blocks
• MD040: Specify language for code blocks

<!-- Good code block -->
Text before

```javascript
const code = 'here';
```

Text after

CLI Commands

# Fix all markdown and MDX files
markdownlint --fix "**/*.{md,mdx}"

# Fix specific files
markdownlint --fix README.md CHANGELOG.md content/blog.mdx

# Check without fixing
markdownlint "**/*.{md,mdx}"

# Use specific config
markdownlint --config .markdownlint.json "**/*.{md,mdx}"

# Ignore specific rules
markdownlint --disable MD013 MD033 "**/*.{md,mdx}"

# Output JSON for parsing
markdownlint --json "**/*.{md,mdx}"

Common Patterns

Fix Multiple Issues at Once

<!-- Before -->
#Title
Some text with trailing spaces
 Tab indented line

- Item 1
* Item 2
Visit http://example.com

<!-- After -->
# Title

Some text with trailing spaces
    Space indented line

- Item 1
- Item 2

Visit <http://example.com>

Add to package.json

{
  "scripts": {
    "lint:md": "markdownlint \"**/*.{md,mdx}\" --ignore node_modules",
    "lint:md:fix": "markdownlint \"**/*.{md,mdx}\" --ignore node_modules --fix"
  }
}

Detailed Rules Reference

For comprehensive documentation of all markdown rules with examples and fixes, see rules-reference.md.

Resources

• markdownlint GitHub
• markdownlint Rules