Markdown Code Fence Language Tag Validator
CodeScan a Markdown document's fenced code blocks and flag a missing, unknown, or inconsistently-cased language tag
Paste a Markdown document and get back a line-by-line list of fenced code blocks whose language tag is missing, unrecognized, or cased differently than convention expects, checked against a curated list of common syntax-highlighter identifiers like js, ts, bash, and yaml. A missing or misspelled tag is a common authoring mistake that silently breaks syntax highlighting on docs sites and in rendered READMEs without ever throwing an error. Fence detection follows CommonMark's rules closely enough for real documents: up to three leading spaces of indentation, a closing fence at least as long as the opening one, and both backtick and tilde fence styles.
How to use Markdown Code Fence Language Tag Validator
- 1.Paste a Markdown document, or try one of the sample snippets to see the output shape.
- 2.Review the flagged lines: each one names whether the tag is missing, unknown, or just cased differently than the lowercase convention.
- 3.Fix the tag in your source document and re-check, since this tool only reports issues, it doesn't rewrite the document for you.
Frequently asked questions
Use via API, SDK, or MCP
cURL# Free: 1,000 req/day · Pro: 10,000 req/day
curl -X POST https://api.utilix.tech/v1/tools/markdown-fence-lang-validator \
-H "Authorization: Bearer utx_live_..." \
-H "Content-Type: application/json" \
-d '{"markdown":"```JS\nconsole.log(1)\n```"}'Get an API key from your dashboard · Full API docs →