How to use this tool

1. Paste a stylesheet, partial rules, or a snippet into the editor.
2. Click Validate. The request is sent to this site’s CSS parse API and returns errors with line/column when the parser fails.
3. Fix the reported spot and re-run until the parse succeeds.

What this check helps you catch

• Unclosed `{` `}` blocks, strings, or comments that break the parse
• Tokens and at-rules the parser rejects as invalid CSS syntax
• Not covered: Autoprefixer/vendor lists, `@supports` truth, security (e.g. `expression()`), or W3C profile conformance — use targeted tools or the W3C validator when you need that

FAQ

Does this prove my CSS works in every browser?

No. It only checks that the text parses as CSS. Use browser devtools, caniuse, or visual testing for compatibility.

Where does validation run?

The page calls this site’s HTTPS API; parsing happens on the server (rate-limited). It is not a fully offline-in-browser check. See the privacy policy for handling.

Is this the official W3C CSS Validator?

No. It uses a PostCSS-based parse for fast syntax feedback. Use the W3C service when you need their specific profiles and messages.

What about minified or generated CSS?

Paste is fine; errors still include line/column. For huge files, prefer validating in your build pipeline or splitting the file.