CSS Validator
Validate and format CSS. Check for syntax errors, missing braces, and invalid properties — all in your browser, no upload.
About the CSS Validator
This CSS validator runs entirely in your browser. Paste your CSS into the box above and click Validate to check for balanced braces and parentheses, missing semicolons, and unknown properties. Click Format to re-indent and tidy your stylesheet.
What it checks
- Balanced braces — Every
{must have a matching}, and vice versa. - Balanced parentheses — Function calls and media queries must close their parentheses.
- Missing semicolons — Declarations that look like
property: valuebut don't end with a semicolon are flagged as warnings. - Unknown properties — Property names not in a built-in list are reported as warnings (vendor-prefixed and custom properties are skipped).
How to use the validator
- Paste your CSS into the input box.
- Click Validate to see errors and warnings, or Format to re-indent the stylesheet.
- Read the result panel for a list of issues with line numbers.
Frequently asked questions
Does this tool upload my CSS? No. All checks happen locally in your browser. Your stylesheets never leave your device.
Is this a full CSS parser? No. It performs structural checks (brace/parenthesis balance, declaration format, known properties). It is a quick linter, not a spec-compliant parser.
Does formatting change my CSS meaning? Formatting only adjusts whitespace and indentation. Selectors, values, and comments are preserved.