CSS Validator & Syntax Checker
Validate your CSS code against W3C standards instantly. Detect syntax errors, invalid properties, and malformed values directly in your browser.
How to Use
A CSS Validator is a tool that analyzes your Cascading Style Sheets (CSS) to ensure they comply with the official W3C specifications. It acts as a strict linter, parsing your code to catch syntax errors, typos, and invalid property values before they cause rendering bugs in production.
How to use the CSS Validator
- Paste your CSS: Simply paste your stylesheet into the CSS Input editor on the left.
- Review Results: The tool instantly parses the input and populates the Validation Results pane on the right.
- Fix Errors: The results are broken down line-by-line into Syntax Errors, Unknown Properties, and Invalid Values.
About This Tool
Why validate your CSS?
- Cross-Browser Consistency: Ensuring your CSS is strictly valid according to the W3C spec reduces the likelihood of unpredictable rendering differences between Chrome, Firefox, and Safari.
- Maintainability: Catching simple typos (
color: readinstead ofcolor: red) early prevents dead code from lingering in your stylesheets. - Performance: Browsers spend less time parsing and discarding invalid rules if your stylesheet is 100% compliant, leading to slightly faster parse times.
While modern browsers are highly fault-tolerant and will simply ignore CSS rules they don't understand, relying on this behavior can mask underlying issues or deprecated properties in your codebase. A validator forces structural integrity.
Why Use This Tool
Client-Side Security
All parsing, lexing, and validation happens directly inside your browser using a WebAssembly/JavaScript port of an AST parser. Your proprietary stylesheets are never uploaded to our servers, ensuring your codebase remains completely private.