Free Markdown Linter — Validate and Fix Markdown Online
Rules covered
- Alt text — flags images with missing alt text (accessibility)
- Heading levels — catches skipped levels (e.g. H1 to H3)
- Empty links — finds links with no URL target
- Line length — warns when lines exceed 120 chars
- Duplicate headings — detects repeated heading text
Good for
- Enforcing style consistency in documentation repos
- Auditing AI-generated markdown output
- Accessibility checks before publishing
- Pre-commit quality gate (paste + review)
Frequently asked questions
Why should I lint my markdown?
Linting catches accessibility issues (missing alt text), structural problems (skipped heading levels), and broken links before they reach your readers or a CI pipeline.
What does the markdown linter check for?
Missing image alt text, skipped heading levels (e.g. jumping from H1 to H3), empty or broken links, lines longer than 120 characters, and duplicate heading text.
How do I fix a skipped heading level warning?
Add the missing heading level between your headings. For example, if you jump from H1 to H3, insert an H2 between them. This is important for document structure and screen reader navigation.
Does the linter upload my markdown to a server?
No. All linting runs locally in your browser. Your document is never sent to a server or stored anywhere.
Need to fix formatting issues? Try the Markdown Formatter or check the syntax reference.