Free Markdown Linter — Check Style Issues
Paste Markdown and instantly get a lint report flagging heading, list, and style issues.
Input Markdown
Lint Report
Markdown Lint Examples
The linter flags style issues: long lines, heading jumps, mixed list markers. Example:
Markdown with common issues
Long line, heading jump (H2 to H3 skipping H1), mixed - and * list markers.
Paste into the editor above to see the lint report. Use Sample to load more.
What Is a Markdown Linter?
You push docs to GitHub, paste into Notion, or deploy to a documentation site — and somewhere in the process the heading hierarchy is broken, a list marker is inconsistent, or blank lines are missing around code blocks. A Markdown linter catches these things before they become visible problems. This tool checks your Markdown against common style rules: heading order (no jumping from H1 to H3), consistent list markers (all - or all *, not mixed), blank lines around blocks, and line length. The CommonMark spec defines the base syntax, and the GitHub Flavored Markdown (GFM) spec defines the extensions most people actually use. The lint report shows issues by line number and severity so you can fix them directly. Check the MDN Markdown guidelines for real-world examples of Markdown quality standards.
This tool runs entirely in your browser. Your Markdown is parsed and analyzed locally—nothing is sent to a server. The lint report lists issues by line with severity (Error, Warning, Info). For formatting Markdown, use Markdown Formatter. For validation, use Markdown Validator.
How to Use This Tool
Paste or Upload
Paste your Markdown into the left editor or click Upload to load a .md, .markdown, or .txt file. Use Sample to load example data with common issues.
Review the Lint Report
The right panel shows the lint report with line numbers and descriptions. Fix issues in the left editor; the report updates automatically. Use Copy or Download to save the report.
Fix and Re-lint
Address each issue and re-run. For converting Markdown to HTML, use Markdown to HTML. For a TOC from headings, use Markdown TOC Generator.
When Markdown Linting Helps
Before committing docs to GitHub or publishing to a CMS, linting catches issues that could break rendering or confuse readers. Inconsistent heading hierarchies make TOCs unreliable. Broken reference-style links cause 404s. Running your Markdown through here improves quality before review.
Documentation sites, README files, and blog posts benefit from consistent Markdown. For converting to HTML for web use, use Markdown to HTML. For generating a table of contents from headings, use Markdown TOC Generator. For syntax reference, use Markdown Cheat Sheet.
Frequently Asked Questions
Is my Markdown data safe here?
Completely safe. All linting runs in your browser using JavaScript — nothing is sent to any server. You can verify this by opening the Network tab in your browser while using the tool: you'll see zero outgoing requests.
What exactly does the linter check?
Typical checks include heading level consistency (no skipping levels), blank lines around headings and code blocks, list marker consistency (all - or all *), line length, and general CommonMark / GFM compliance. The exact rules depend on the implementation used.
What's the difference between a linter and a validator?
A linter focuses on style and best practices — things that are technically valid but inconsistent or hard to read. A validator checks that the syntax parses correctly. Both are useful. For syntax validation, try Markdown Validator.
Does it support GitHub Flavored Markdown?
Yes. Most linters support GitHub Flavored Markdown extensions like tables, task lists, and strikethrough. Check the lint report for GFM-specific issues.
Can it fix issues automatically?
This tool reports issues so you can fix them manually. For automatic whitespace and line break fixes, use the Markdown Formatter which applies consistent formatting.
Related Tools
For Markdown syntax, see CommonMark and CommonMark spec. GitHub Flavored Markdown extends it. Markdown Guide offers tutorials. See also GitHub, W3C HTML, and Jekyll.