Make README files, docs and blog posts look right everywhere. The checker follows common markdownlint rules: heading levels that skip, more than one H1, “#Title” without a space, empty or reversed links, undefined reference links, images without alt text, code blocks that are never closed or have no language, bare web addresses, mixed list markers, tabs and stray trailing spaces.
loading toolHow to use the markdown checker
- Paste your code into the box (or tap Try a sample).
- Read the list of problems: ✕ marks an error, ! a warning.
- Tap Show next to a problem to jump to that line, fix it, and watch the list update.
Good to know
- Give every code block a language, like ```js, for colours on GitHub.
- Exactly two spaces at the end of a line make a line break; use a blank line for a new paragraph.
Questions
Why does a missing space after # matter?
Most Markdown apps, including GitHub, only treat “# Title” as a heading. “#Title” shows as plain text with a hash in front.
Why is a bare link a warning?
Some apps turn https://… into a link and some do not. Writing <https://…> or [text](https://…) works everywhere.
Is my data private?
Yes. Everything happens inside your own browser: nothing you type or choose is uploaded to us or anyone else.
Is it free?
Completely free, with no sign-up, no watermark and no limit on how many times you use it. Light ads keep the site running.
