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Linting & Formatting with markdownlint & Prettier0%
Linting & Formatting with markdownlint & Prettier
Beginner12 min read•Updated: Jul 11, 2026
When dozens of software engineers collaborate on open-source repositories or company documentation wikis, inconsistent formatting quickly creeps in: some developers use two spaces for lists, others use four; some leave blank lines around headings, others omit them; broken links and duplicate headings go unnoticed.
markdownlint and Prettier automate code style enforcement, catching errors before they reach production.
Click to Zoom1. What is markdownlint?
markdownlint is a static analysis tool that inspects Markdown files against a set of standardized quality rules. It is available as a VS Code extension, a Node.js CLI tool (markdownlint-cli), and a GitHub Action.
Top Common markdownlint Rules:
- MD001 / heading-increment: Heading levels should only increment by one level at a time (e.g., cannot jump from
#directly to###). - MD009 / no-trailing-spaces: Disallows unintentional trailing whitespace at the ends of lines.
- MD013 / line-length: Recommends wrapping lines at 80 or 120 characters for clean terminal viewing.
- MD022 / blanks-around-headings: Headings must be surrounded by blank lines.
- MD025 / single-title: A document should have only one top-level
# H1heading. - MD033 / no-inline-html: Flags raw HTML elements when strict pure-markdown compliance is desired.
2. Configuring markdownlint (.markdownlint.json)
You can customize or disable specific rules for your project by adding a .markdownlint.json configuration file in the project root:
{
"default": true,
"MD013": false,
"MD033": {
"allowed_elements": ["details", "summary", "kbd", "img", "br"]
},
"MD024": {
"siblings_only": true
}
}
3. Formatting with Prettier
Prettier is an opinionated code formatter that supports Markdown and CommonMark out of the box:
- Automatically wraps lines consistently.
- Cleans up uneven list indentation.
- Formats pipe tables so columns line up neatly.
Running Prettier via Terminal:
# Check for formatting violations
npx prettier --check "**/*.md"
# Automatically format and fix all markdown files
npx prettier --write "**/*.md"
4. Automating Linting in GitHub Actions CI
Catch broken markdown automatically on every Pull Request by adding a GitHub Actions workflow:
# .github/workflows/lint-markdown.yml
name: Lint Markdown
on: [push, pull_request]
jobs:
lint:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v4
- name: Run markdownlint
uses: DavidAnson/markdownlint-cli2-action@v16
with:
globs: "**/*.md"
Interactive Quiz
Multiple Choice Questions
Question 1
Which static analysis tool is widely used to detect style inconsistencies and syntax violations in Markdown?
Question 2
What does markdownlint rule 'MD001' enforce?
Question 3
What command formats all Markdown files in a repository automatically using Prettier?
Question 4
What configuration filename is used to customize markdownlint rules in a repository?
Question 5
Why is integrating markdownlint into a continuous integration (CI) pipeline beneficial?
Next Lesson
Converting Markdown to HTML, PDF & Slides (Marp/Pandoc)
Continue learning with hands-on practice, examples, and exercises in the upcoming topic.
Related Lessons
| Previous Lesson | Next Lesson |
|---|---|
| Markdown in Modern SSGs & MDX (Astro, Next.js) | Converting Markdown to HTML, PDF & Slides (Marp/Pandoc) |
Practice Quiz
Test your understanding of this lesson with 5 questions. Each question has one correct answer.