A Markdown linter checks your Markdown documents for style inconsistencies, formatting errors, and best practice violations. Consistent Markdown improves rendering across different parsers, makes documentation more readable, and reduces errors on documentation sites like GitHub Pages and MkDocs — paste your Markdown below to see issues.
Active Rules
How to Use the Markdown Lint Validator
A Markdown linter enforces consistent style across your documentation. The rules in this
tool follow the same naming convention as the popular markdownlint
library (MD001, MD009, etc.) so you can use the rule documentation directly.
Step 1: Paste Your Markdown
Paste your Markdown document into the input area. You can use the "Load example" button to see what Markdown with common issues looks like. The validator works on any Markdown content — README files, documentation pages, blog posts, or any other Markdown text.
Step 2: Select Rules (Optional)
The rules sidebar on the right shows all active rules. Uncheck any rule that conflicts with your project's style guide. For example, if your project allows long lines, uncheck MD013. Your rule selection is applied immediately when you run the linter.
Step 3: Click Lint Markdown
Results are grouped by severity. Click any issue row to see which line in your document caused it.
Each issue shows the rule ID (like MD025),
line number, and a description of what to fix.
Key Rules to Know
The most impactful rules are: MD001 (heading levels must increment by one — no jumping from
H1 to H3), MD025 (only one H1 per document — critical for SEO), MD034
(URLs should use [text](url) syntax or be
wrapped in angle brackets, not bare), and MD022 (headings need blank lines before and after
for consistent rendering across parsers).
FAQ
Is this Markdown linter free?
Yes, completely free with no account required. Paste your Markdown and get lint results instantly. All processing runs in your browser — no data is uploaded anywhere.
Is my Markdown content private?
Yes. Everything runs locally in your browser. Your Markdown text is never sent to any server and is not stored or logged.
What Markdown lint rules does this tool check?
It checks 15+ rules including: MD001 (heading levels increment by one), MD009 (no trailing spaces), MD010 (no hard tabs), MD012 (no multiple blank lines), MD013 (line length), MD018/MD019 (heading hash spacing), MD022 (headings surrounded by blank lines), MD025 (single H1), MD034 (no bare URLs), MD041 (first line is H1), and more.
Can I turn off specific lint rules?
Yes. Each rule has a checkbox to enable or disable it. If a rule conflicts with your project's style guide, simply uncheck it. Your rule preferences are applied immediately on re-validation.
What is the difference between markdownlint and this tool?
This tool implements the same rule IDs as the popular markdownlint library (MD001, MD009, etc.) and checks for the same common issues, making it compatible with markdownlint configuration and rule documentation. It runs entirely in the browser without requiring Node.js.
Why should I lint my Markdown?
Consistent Markdown style improves readability, prevents rendering issues across different Markdown parsers, and makes collaborative editing easier. For documentation sites like GitHub Pages, MkDocs, or Docusaurus, clean Markdown produces cleaner HTML output.