CSS Validator — Syntax Error Checker
Validate CSS syntax instantly in your browser. Get real-time feedback on errors and warnings with exact line and column numbers. Shows rule count, declarations, selectors, at-rules, and comment statistics.
How to Use CSS Validator — Syntax Error Checker
How to Use the CSS Validator:
Paste Your CSS: Type or paste your CSS into the input area. Validation happens in real-time as you type — no button press needed.
Read the Status Banner: A green "Valid CSS" banner means your CSS is syntactically correct. A red "Invalid CSS" banner shows the number of errors found.
Fix Issues: The Issues panel lists every error and warning sorted by line number. Each item shows the line, column, and a description of the problem.
Review Statistics: The Statistics panel shows line count, rule count, declarations, selectors, at-rules, and comment count for your stylesheet.
Use Examples: Click the example buttons (Button styles, Flexbox layout, Variables + @media, Animation, Invalid) to load sample CSS and see how the validator works.
Clear: Click the Clear button to reset the editor and start fresh.
Errors detected:
- Unclosed comment — a /* comment was opened but never closed with */
- Missing selector before { — an opening brace appears with no selector before it
- Unexpected } — a closing brace appears without a matching opening brace
- Unclosed { — an opening brace was never closed
Warnings detected:
- Missing colon — a declaration inside a rule block has no colon (e.g.
color redinstead ofcolor: red) - Duplicate property — the same CSS property appears more than once in the same rule block
Common CSS Mistakes:
- Forgetting to close a rule block with }
- Writing
color redinstead ofcolor: red - Leaving a /* comment open without closing it
- Accidentally duplicating a property like
marginin the same rule
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