CSS Validator
Paste up to 1 MiB of CSS for a bounded browser-side check. CSSOM may recover invalid CSS, so this is not a full standards or lint validator.
A QUICK WALKTHROUGH
How to use this tool
- Paste CSS up to 1 MiB.
- Run the local CSSOM check.
- Review the parsed-rule count and structural warnings.
Browser CSSOM check
The tool creates a detached style element and reads its CSSOM rules to confirm what the browser parsed.
Basic structural warnings
It detects unclosed comments, strings, and blocks before CSSOM parsing and reports parse recovery limitations.
Local and bounded
Input stays in this browser, is limited to 1 MiB, and is never sent to a server.
GOOD TO KNOW
Common questions
Does a clean result prove standards compliance?
No. Browser CSSOM parsing can recover from invalid CSS, and this tool is not a complete standards or lint validator.
Does it upload my CSS?
No. The input is parsed in a detached browser document.