Developer ToolsCode ValidatorsFree Tool
CSS Validator
Run basic heuristic checks on CSS — mismatched braces, likely missing semicolons, and empty rule blocks — not a full W3C validation.
How to Use CSS Validator
- 1Paste your CSS code
- 2Click Process
- 3Review any flagged issues, or the full W3C validator link for a thorough check
Frequently Asked Questions
Three heuristics: whether the count of opening and closing braces match, whether there are likely missing semicolons before line breaks, and whether any selector has an empty rule block ({} with nothing inside).
No — it's a lightweight heuristic pass, not a real CSS parser or spec-compliant validator. It won't catch invalid property names, bad values, or many real CSS errors. The tool's own output links to jigsaw.w3.org/css-validator for full W3C validation.
Yes — because it's regex/heuristic-based rather than a true parser, it can flag things that are actually valid CSS, or miss genuinely invalid CSS that doesn't match its specific checks.
No — all checks run in your browser; nothing is uploaded.
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