Markdown Linter
CodeLint Markdown for broken #anchor links, skipped heading levels, undefined links and footnotes, missing alt text, untagged code fences, bad blockquote nesting and open tasks, with line numbers
Related tools: Markdown Table of Contents Generator · Markdown Table Column Aligner · Markdown Front Matter Parser · Markdown Preview · Mermaid Diagram Syntax Validator
About Markdown Linter
Paste a README, docs page or blog post and the Markdown Linter runs eight checks at once, listing every finding with its line number: heading levels that skip (H2 straight to H4), #anchor links that point to a heading that does not exist, reference-style links and footnotes that are used but never defined or defined but never used, images with missing or meaningless alt text, code fences without a language tag, blockquotes that jump nesting levels, and unchecked task-list items. Every rule is on by default and can be switched off on its own, and clicking a line number selects that line in the editor so you can fix it in place. It is deliberately narrower than markdownlint: it skips whitespace and formatting nitpicks and concentrates on problems that break rendering, navigation or accessibility once the document is published. It runs entirely in your browser, and each rule is also its own REST endpoint, SDK function and MCP tool for CI checks and agents.
How to use Markdown Linter
- 1.Paste your Markdown into the editor; all eight rules run as you type and findings appear sorted by line number with a severity (error, warning or info).
- 2.Switch off rules that do not apply (for example open tasks in a working draft) with the toggles above the editor; the badge on each toggle shows how many findings that rule produced.
- 3.Click a line number in the results to select that line in the editor, fix it, and watch the finding disappear.
- 4.Group results by rule to work through one kind of problem at a time, then use Copy report to paste the list into a pull request review or issue.