LLM markdown linter
LLMs are fluent markdown writers, but they leave small messes: trailing spaces, bare URLs that should be links, heading levels that jump from H2 to H4, and code fences they forget to close. Those render badly or break entirely once the text leaves the chat box. This linter checks for the most common offenders and auto-fixes the safe ones, all in your browser.
The most common LLM markdown problems
Unclosed code fences are the most disruptive. A triple-backtick block that opens but never closes causes everything after it to render as a code block — often making the rest of a long document appear as monospace text. Models tend to produce unclosed fences when they generate code examples mid-stream and lose track of the fence state.
Heading jumps are ubiquitous. A model may jump from ## Section directly to #### Sub-subsection, skipping ### entirely. This breaks accessibility tools, navigation sidebars in documentation platforms, and automated TOC generators. Many renderers also produce malformed HTML when heading levels are non-sequential.
Bare URLs look fine in a raw chat window, but in a rendered doc they appear as unlinked plaintext and may not even be clickable. Wrapping them as [text](url) takes two seconds manually but is easy to miss across a long response.
Trailing whitespace is invisible and usually harmless in rendered output, but it can trigger linting failures in documentation pipelines, break diff readability in version-controlled docs, and cause unexpected behavior in some markdown parsers.
How it works
The tool scans your markdown line by line. It flags trailing whitespace, hard tabs, runs of three or more blank lines, and bare URLs not wrapped as links. It tracks heading levels to catch jumps greater than one (an H2 followed directly by an H4), and it counts triple-backtick fences to warn when one is opened but never closed. Each finding shows a line number and a plain-language reason. Auto-fix rewrites only the whitespace issues that are always safe to change.
Which checks auto-fix and which are reported only
| Issue | Auto-fixed? |
|---|---|
| Trailing whitespace | Yes |
| Hard tabs | Yes |
| Multiple consecutive blank lines | Yes |
| Bare URLs | No — wrapping requires choosing link text |
| Heading level jumps | No — repair depends on intent |
| Unclosed code fences | No — closing location requires judgment |
Tips and notes
- Fix structure by hand. Heading jumps and unclosed fences are reported, not auto-fixed, because the right repair depends on intent.
- Bare URLs are a frequent LLM tell. Wrap them as
[text](url)so they render as proper links and read cleanly. - Run it before committing docs. Catching whitespace and fence issues here keeps your rendered docs and READMEs tidy.
- Re-lint after auto-fix. A clean second pass confirms only the structural items remain for you to address.