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ToolsCSS Validator

CSS Validator

Validate your CSS code to ensure it follows CSS3 standards and best practices.

CSS Code
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Validation Results
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Enter your CSS code and click "Validate CSS" to check for issues.

CSS Validation Guide

CSS validation is the process of checking your CSS code against the official CSS standards to ensure it's properly formatted and structured. Valid CSS is important for several reasons:

Benefits of CSS Validation

  • Cross-browser Compatibility: Valid CSS is more likely to render consistently across different browsers.
  • Easier Debugging: Finding and fixing issues is simpler with validated code.
  • Better Performance: Browsers process valid CSS more efficiently.
  • Future-proof Code: Code that follows standards is less likely to break with browser updates.
  • Maintainability: Clean, valid CSS is easier to maintain and extend.

Common CSS Validation Issues

  • Missing or mismatched braces
  • Missing semicolons between declarations
  • Invalid property names or values
  • Incorrect syntax in selectors
  • Incorrect use of media queries
  • Malformed color values
  • Unknown or deprecated properties

CSS3 Best Practices

  • Use appropriate selectors to minimize specificity issues
  • Organize properties consistently within rules
  • Group related styles together
  • Comment your code for clarity
  • Use shorthand properties when appropriate
  • Minimize use of !important
  • Consider using a CSS preprocessor for complex projects
  • Use CSS variables for consistent values
Related Tools
HTML ValidatorValidate HTML for standards compliance
CSS MinifierCompress your CSS files
JavaScript MinifierMinify your JavaScript code
Expert Tips

Use a CSS Linter

Tools like Stylelint can automatically catch errors and enforce style conventions during development.

Consider BEM Methodology

Block Element Modifier (BEM) naming conventions can help organize CSS and prevent conflicts.

Use CSS Custom Properties

CSS variables (custom properties) make your stylesheets more maintainable and consistent.

FAQ

Why does my valid CSS look different in browsers?

Browsers have different default styles and may implement certain CSS features differently, even with valid code.

Should I validate CSS after preprocessing?

Yes, always validate the compiled CSS output from preprocessors like Sass or Less, not just the source files.

What about vendor prefixes?

Consider using Autoprefixer to automatically add vendor prefixes where needed instead of manually writing them.