CSS Validator
CSS Validator
Paste input, adjust settings if needed, then run.
Check CSS syntax basics such as balanced braces and declaration structure.
Result size
0chars
Run to update output.
Output summary
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More actions
Input: manual
Input: manualInputsTextManual input • Auto-updateWaiting
Status
Waiting for output.
Health 55/100
Result sizeLive
0chars
Run to update output.
Copy result = output only. Copy report = output + settings.
Privacy note
Your input is processed locally in your browser whenever possible. We do not store your data.
Flow
- Parse CSS rules and declarations from input text.
- Detect invalid tokens, malformed blocks, and declaration errors.
- Return pass/fail state with actionable parser messages.
Example
Worked example: missing semicolon
- 1 Input contains `color: red` followed by another property without a separator.
- 2 Validator reports the declaration parse issue.
- 3 After adding the missing semicolon, the report returns valid.
The corrected stylesheet passes syntax checks cleanly.
How
- Paste CSS into the validator input.
- Run syntax validation and review diagnostics.
- Fix flagged lines, then re-run until the report is clean.
Cases
- Catch missing braces and invalid declarations before shipping.
- Validate copied snippets from design systems or tutorials.
- Troubleshoot style regressions in pull requests.
Avoid
- Confusing syntax validity with visual design correctness.
- Ignoring parser line numbers and fixing the wrong block.
- Pasting SCSS/LESS syntax into a plain CSS validator.
FAQ
Does css validator send my input to a server?
No. CSS Validator handles the input in your browser whenever possible, so routine conversions, previews, and copy actions stay on your device instead of being sent to Calctrove servers.
Does this validate SCSS or LESS?
This tool validates plain CSS syntax. Preprocessor syntax may require separate tooling.
Can valid CSS still render incorrectly?
Yes. Syntax can be valid while layout logic is still wrong due to specificity or cascade behavior.
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