CSS Validator

Validate CSS code for syntax errors, invalid rules, and compatibility issues with our free online CSS validator tool.

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About This Tool

The CSS Validator tool helps developers check CSS code for syntax errors, invalid properties, unsupported values, and potential compatibility issues. Simply paste your CSS code or upload a .css file, and get a detailed report with line numbers, error descriptions, and suggestions for fixes. The tool validates against W3C CSS standards and provides warnings for deprecated properties and browser compatibility concerns.

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How to Use

Paste your CSS code into the textarea or upload a .css file
Choose validation options (strict mode, browser compatibility checks)
Click 'Validate CSS' to analyze your code
Review the detailed report with errors, warnings, and statistics
Fix issues based on the line-by-line feedback provided

Frequently Asked Questions

Find Quick Answers

What CSS standards does this validator check against?

The validator checks against W3C CSS specifications including CSS Level 1, 2.1, and 3 standards, with options for strict or relaxed validation.

Can I validate CSS for specific browser compatibility?

Yes, the tool includes browser compatibility checks and can warn about properties not supported in specific browser versions.

Does the tool support CSS preprocessors like SASS or LESS?

This validator focuses on pure CSS syntax. For SASS or LESS validation, you would need to compile them to CSS first before validation.

Is there a file size limit for CSS uploads?

The tool can handle CSS files up to 5MB in size, which covers most practical CSS codebases and frameworks.

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