Markdown Linter
Paste your Markdown and get a line-by-line list of style and structure issues — heading levels, list markers, trailing whitespace, and more. Auto-fix what's fixable with one click.
Runs entirely in your browser — files never leave your device.
- L1MD022/blanks-around-headingsFixable
Headings should be surrounded by blank lines (Expected: 1; Actual: 0; Below)
- L2MD001/heading-increment
Heading levels should only increment by one level at a time (Expected: h2; Actual: h3)
- L2MD022/blanks-around-headingsFixable
Headings should be surrounded by blank lines (Expected: 1; Actual: 0; Above)
- L6MD032/blanks-around-listsFixable
Lists should be surrounded by blank lines
- L7MD004/ul-styleFixable
Unordered list style (Expected: dash; Actual: asterisk)
- L7MD032/blanks-around-listsFixable
Lists should be surrounded by blank lines
- L9MD040/fenced-code-language
Fenced code blocks should have a language specified
How it works
- 01Paste or upload your Markdown, or click Sample to try a document with several intentional issues.
- 02The issues list updates automatically as you type, showing the line number, rule, and a plain-language message for each finding — issues tagged "Fixable" can be resolved automatically.
- 03Click Fix to auto-resolve every fixable issue in place; issues that need a judgment call (like a skipped heading level) are left for you to fix by hand. Click Undo to revert the last Fix.
- 04Open Rules to turn off individual rules — grouped by category (Headings, Lists, Whitespace, and more) — if a rule doesn't match your house style. Your choices are remembered in this browser.
- 05Copy the report as plain text to share in a code review or commit message.
Frequently asked questions
Is this Markdown linter (validator) free?
Yes, with no account or limits. Linting and auto-fixing both run entirely in your browser's JavaScript engine using markdownlint's rule set.
Does my Markdown get uploaded anywhere?
No. Linting happens entirely client-side — the text you paste never leaves your device (unless you use "Open from URL" to fetch a remote file, which is a direct browser request, not a server relay).
What kinds of issues does it catch?
Heading level jumps (e.g. H1 straight to H3), inconsistent list markers, missing blank lines around headings and lists, trailing whitespace, and dozens of other common Markdown style issues from markdownlint's default rule set.
Does this tool fix issues automatically?
Yes for the issues markdownlint knows how to fix mechanically (trailing whitespace, list marker style, missing blank lines, and similar) — click Fix and they're resolved in place, with one level of Undo. Issues that require a judgment call, like a skipped heading level or a duplicate heading, aren't auto-fixable and stay listed for you to resolve by hand.
Can I turn off specific rules?
Yes — open the Rules panel to uncheck any rule, grouped by category. Disabled rules are excluded from linting entirely (not just hidden from the list) and your choice is saved in this browser for next time. Line length (MD013) is off by default since long, unwrapped prose lines are normal Markdown style.
Is this the same as markdownlint?
Yes — it runs the actual markdownlint (MIT-licensed) library in your browser, the same engine used by the popular VS Code and CLI linters, just without an install step.
Related tools
Markdown validator
Looking for a Markdown validator rather than a linter? Same tool — “linting” and “validating” Markdown both mean checking a document against a set of structural and style rules (rather than checking whether it parses at all, since nearly any text is technically valid Markdown). This tool validates structure and style: heading hierarchy, list consistency, and whitespace — the issues that make Markdown render inconsistently across renderers or look unpolished in a diff.