Free CSS Validator
Paste your CSS code to check for syntax errors, invalid properties, and incorrect values. Get a quality score with detailed reports.
Syntax Checking
Catch syntax errors, missing semicolons, unclosed brackets, and malformed declarations instantly.
Property Validation
Verify that CSS properties and values are valid according to the latest CSS specification.
Quality Score
Get a 0-100 score and letter grade for your CSS quality. Track improvements as you fix issues.
Common CSS Errors
Missing Semicolons
Forgetting a semicolon at the end of a declaration causes the next property to be ignored or misinterpreted.
Invalid Property Names
Typos in property names like 'colr' instead of 'color' are silently ignored by browsers, making bugs hard to find.
Invalid Values
Using incorrect values like 'display: flexbox' instead of 'display: flex' won't produce errors in the browser, just broken layouts.
Unclosed Brackets
Missing closing braces cause all subsequent rules to be nested inside the wrong selector.
Missing Units
Numeric values (except 0) require units. 'width: 100' won't work, use 'width: 100px' or 'width: 100%'.
Invalid Selectors
Malformed selectors like '.class.' or '#id#id' are silently discarded by the browser.
Why Validate Your CSS?
Unlike HTML, CSS fails silently. Invalid properties and values are simply ignored by browsers without any error messages. This makes CSS bugs particularly hard to track down — a typo in a property name can cause hours of debugging.
Validating your CSS catches these silent failures before they reach production. It helps you identify typos, deprecated properties, browser compatibility issues, and syntax errors that could break your layout.
Clean, valid CSS also improves page performance. Invalid declarations force browsers to do extra parsing work, and redundant or conflicting rules increase file size without benefit.