Free Online CSS Validator
Validate CSS syntax with detailed error messages and line numbers. Format CSS with proper indentation.
palette Input CSS
Characters: 0
Lines: 0
Rules: -
Properties: -
code Output Result
Click Validate to check CSS syntax, or Format to beautify CSS.
Key Features
Instant Validation
Check CSS for unbalanced braces, missing semicolons, and invalid property-value pairs.
Error Detection
Each error and warning includes the exact line number for quick style debugging.
CSS Formatting
Beautify CSS with automatic 2-space indentation for clean, readable stylesheets.
Privacy Protected
All processing happens locally in your browser. No data ever leaves your device.
Frequently Asked Questions
Getting Started
What is a CSS validator?
The CSS Validator checks your stylesheets for syntax errors that would prevent rules from being applied correctly. It detects unbalanced braces, missing semicolons, invalid property names, unsupported values, and empty rule blocks.
Is this CSS validator free?
Yes. All tools are completely free and run locally in your browser. No signup, no limits, no hidden costs.
Does the tool store my data?
No. Your CSS data never leaves your browser. All processing happens locally on your device, ensuring complete privacy and security.
Features & Usage
Does this validator check for browser compatibility?
No, this validator checks CSS syntax and property validity, not browser support. For browser compatibility data, use caniuse.com or run your CSS through Autoprefixer.
How is this different from Stylelint?
This CSS validator focuses on syntax correctness -- valid property names, balanced braces, semicolons between declarations. Stylelint is a linter that enforces coding conventions like selector class patterns, max specificity depth, and disallowed units.
Can this tool validate SCSS, Less, or other preprocessor syntax?
No, this validator expects plain CSS. SCSS and Less add features like variables, nesting, mixins, and parent selectors that are not valid CSS syntax. Validate the compiled CSS output instead.
What does the validator do with CSS custom properties (variables)?
CSS custom properties like --main-color and their usage via var() are fully supported by the validator. They are valid CSS syntax defined by the CSS Custom Properties specification. The validator checks function correctness but does not verify that every referenced property is defined.