markdownlint

PovertyAction's avatarfrom PovertyAction

This skill should be used when users need to format, clean, lint, or validate Markdown files using the markdownlint-cli2 command-line tool. Use this skill for tasks involving Markdown file quality checks, automatic formatting fixes, enforcing Markdown style rules, or identifying Markdown syntax issues.

⭐3stars🔀2forks📁View on GitHub🕐Updated Dec 29, 2025
[Technical Writing]

When & Why to Use This Skill

The Markdownlint skill is a specialized utility designed to automate the formatting, linting, and validation of Markdown files using the markdownlint-cli2 engine. It helps maintain high-quality documentation by enforcing consistent style rules, identifying syntax errors, and providing automatic fixes, ensuring that your READMEs, guides, and Quarto Markdown (.qmd) files are professional and error-free.

Use Cases

  • Automated Style Enforcement: Automatically apply and enforce project-specific Markdown style guides (e.g., indentation, heading styles) to ensure consistency across large documentation sets.
  • Syntax Validation and Cleaning: Identify and resolve common Markdown syntax issues, such as broken headers, missing alt text for images, or improper list nesting, before publishing.
  • Batch Formatting: Use the auto-fix capability to instantly clean up and reformat multiple Markdown files or entire directories, saving significant manual editing time.
  • Documentation Quality Assurance: Integrate linting into the writing workflow to catch errors early, ensuring that documentation is ready for version control or static site generation.
namemarkdownlint
descriptionThis skill should be used when users need to format, clean, lint, or validate Markdown files using the markdownlint-cli2 command-line tool. Use this skill for tasks involving Markdown (including Quarto Markdown `.qmd`) file quality checks, automatic formatting fixes, enforcing Markdown style rules, or identifying Markdown syntax issues.

Markdownlint Skill

Contents

Project Configuration

IMPORTANT: This project uses .markdownlint.yaml. Always follow these rules:

Rule Setting Notes
MD040 Enabled Always specify language for code fences
MD007 2 spaces List indentation
MD024 Siblings only Duplicate headings allowed under different parents
MD013 Disabled No line length restrictions
MD033 Disabled Inline HTML allowed
MD041 Disabled Files don't need to start with H1
MD038 Disabled Spaces in code spans allowed
MD036 Disabled Emphasis as heading allowed

Basic Usage

# Lint files
markdownlint-cli2 "**/*.md"
markdownlint-cli2 README.md

# Auto-fix issues
markdownlint-cli2 --fix "**/*.md"

# Exclude directories
markdownlint-cli2 "**/*.md" "#node_modules" "#vendor"

Common Operations

Lint Specific Paths

markdownlint-cli2 README.md                    # Single file
markdownlint-cli2 "docs/**/*.md"               # Directory
markdownlint-cli2 "*.md" "docs/**/*.md"        # Multiple patterns
markdownlint-cli2 .                            # Current directory

Auto-Fix

markdownlint-cli2 --fix "**/*.md"              # Fix all files
markdownlint-cli2 --fix README.md              # Fix single file

Process stdin

cat README.md | markdownlint-cli2 -

Workflow

Standard Lint-Fix-Verify Cycle

  1. Run lint check: markdownlint-cli2 "**/*.md"
  2. Review reported issues
  3. Apply auto-fix: markdownlint-cli2 --fix "**/*.md"
  4. Re-run lint to verify: markdownlint-cli2 "**/*.md"
  5. Review changes: git diff
  6. Commit when satisfied

Safe Fix with Backup

  1. Stage current state: git add .
  2. Create backup commit: git commit -m "Backup before markdownlint fix"
  3. Apply fixes: markdownlint-cli2 --fix "**/*.md"
  4. Review changes: git diff
  5. Commit fixes or reset: git add . && git commit -m "Apply markdownlint fixes"

Cross-Platform Usage

For maximum compatibility:

  • Quote glob patterns: markdownlint-cli2 "**/*.md"
  • Use # for negation: markdownlint-cli2 "**/*.md" "#vendor" (not !)
  • Use forward slashes: docs/**/*.md (works on all platforms)
  • Stop option processing: markdownlint-cli2 -- "special-file.md"

Troubleshooting

No Files Matched

  • Verify glob patterns are quoted
  • Check file extensions (.md vs .markdown)
  • Ensure negated patterns don't exclude everything

Too Many Issues

  1. Start with auto-fix: markdownlint-cli2 --fix "**/*.md"
  2. Disable problematic rules temporarily
  3. Address remaining issues incrementally

Configuration Not Loading

  • Verify configuration file name matches expected patterns
  • Validate JSON/YAML syntax
  • Use --config to explicitly specify the file

References

Installation

npm install -g markdownlint-cli2    # npm
brew install markdownlint-cli2      # Homebrew
markdownlint-cli2 --help            # Verify installation