CSS Validator
Check CSS syntax for errors instantly
Free online CSS validator to check your CSS code for syntax errors, invalid properties, and common mistakes. Validate CSS instantly in your browser. Perfect for debugging and ensuring code quality. No installation required.
How to validate CSS code?
Validating your CSS is quick and straightforward:
- Paste your CSS code into the input box. You can paste entire stylesheets, single rules, or snippets you're unsure about.
- The validator automatically checks your code as you type. Any errors or warnings will appear immediately below the input.
- Review the validation results. Errors are marked clearly with line numbers and descriptions to help you fix issues quickly.
- Fix any errors and re-validate. The tool updates in real-time, so you can see results instantly as you correct your code.
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Why validate CSS? The importance of clean code
Let's be honest - CSS errors are frustrating. They can break your entire layout, cause styles to not apply, or create unexpected visual issues. But here's the thing: catching errors early saves hours of debugging later. When you validate CSS, you're not just checking syntax - you're ensuring your styles work consistently across browsers, preventing layout breaks, and maintaining code quality. Invalid CSS can cause browsers to ignore entire rulesets, meaning your carefully crafted styles might not apply at all. Worse, some errors are silent - your page might look fine in one browser but break completely in another. Validation catches these issues before they become problems. Plus, clean, valid CSS is easier to maintain, debug, and collaborate on. Your future self (and your teammates) will thank you for taking the time to validate.
Common CSS errors that validation catches
- Missing semicolons: Forgetting semicolons between properties breaks entire rulesets. The validator catches these immediately so you can fix them before they cause issues.
- Unclosed brackets: Missing closing braces can break your entire stylesheet. Validation identifies exactly where brackets are missing or mismatched.
- Invalid property values: Using values that don't exist for a property (like 'center' for 'color') gets caught before browsers ignore your styles.
- Typos in property names: Simple typos like 'backgound' instead of 'background' are easy to miss but break your styles. Validation catches these instantly.
- Invalid selectors: Malformed selectors won't match anything. The validator helps you write correct selectors that actually work.
- Browser compatibility issues: Some properties or values aren't supported everywhere. Validation can warn you about potential compatibility problems.
- Syntax errors: Basic syntax mistakes like missing colons, incorrect nesting, or invalid characters get flagged immediately.
Frequently Asked Questions (FAQs)
What does CSS validation check for?
CSS validation checks for syntax errors like missing semicolons, unclosed brackets, invalid property names or values, malformed selectors, and common mistakes that could break your stylesheet. It helps ensure your CSS is well-formed and will work correctly across browsers.
Will valid CSS always work perfectly?
Valid CSS means your syntax is correct, but it doesn't guarantee browser compatibility or that your styles will look exactly as intended. However, valid CSS is much more likely to work consistently. Invalid CSS, on the other hand, can cause browsers to ignore entire rulesets, leading to broken layouts.
Does this tool upload my CSS to a server?
No, all validation happens entirely in your browser. Your CSS code never leaves your computer, ensuring complete privacy and security. This is especially important if you're working with proprietary or confidential stylesheets.
Can I validate CSS from external files?
This tool validates CSS code that you paste directly. For validating CSS from external files, you would need to copy the CSS content and paste it into the validator. The tool focuses on syntax validation rather than checking external resources.
What if my CSS uses vendor prefixes?
Vendor prefixes like -webkit-, -moz-, or -ms- are valid CSS syntax and won't cause validation errors. The validator checks for proper syntax, not browser-specific features. However, it's worth noting that many vendor prefixes are no longer needed in modern CSS.
How accurate is the validation?
The validator checks CSS syntax according to CSS specifications. It catches syntax errors, invalid properties, and common mistakes accurately. However, it validates syntax only - it doesn't check browser compatibility or whether your styles will achieve the visual result you want.