A CSS Compatibility Linter scans your stylesheet code and checks whether the CSS properties, functions, selectors, and at-rules you've used are supported across different web browsers (Chrome, Firefox, Safari, Edge, Opera, Samsung Internet, etc.). This is crucial because not all browsers support the latest CSS features at the same time. Using unsupported CSS can lead to broken layouts, missing styles, or degraded user experiences for visitors using older or less common browsers. Our tool instantly highlights potential compatibility issues so you can fix them before deploying to production.

Our tool maintains an extensive compatibility database that maps CSS features to the minimum browser versions that support them. When you input your CSS, the tool parses it to extract all properties, functions, at-rules, and selectors, then cross-references each one against the database for your selected target browsers. The database is regularly updated to reflect the latest browser release data, inspired by authoritative sources like Can I Use and MDN Web Docs. Each feature is evaluated per browser, and results are color-coded: green for full support, yellow for partial support or vendor-prefix requirements, and red for no support.

Partial Support means the CSS feature works but may require a vendor prefix (like -webkit- or -moz-), may have limited functionality, or is only supported in newer versions of that browser. For example, backdrop-filter works in Safari 9+ but required the -webkit-backdrop-filter prefix in early versions. Not Supported means the browser simply does not implement that CSS feature at all in the selected version baseline, so it will have no effect. In these cases, you should consider fallback styles or progressive enhancement strategies.

There are several strategies to handle compatibility issues:

• Add vendor prefixes: Use tools like Autoprefixer to automatically add -webkit-, -moz-, -ms- prefixes where needed.
• Provide fallback values: Declare a widely-supported alternative before the modern property (e.g., background: #fff; background: linear-gradient(...);).
• Use @supports feature queries: Wrap cutting-edge CSS in @supports (property: value) { ... } to only apply it in supporting browsers.
• Progressive enhancement: Build a solid base experience that works everywhere, then layer on modern features for browsers that support them.
• Polyfills: Some CSS features have JavaScript polyfills that emulate support in older browsers.

Some CSS features that frequently cause cross-browser issues include: backdrop-filter (limited Safari support in older versions), aspect-ratio (not supported in older Safari), gap in flexbox (only supported since Chrome 84+ and Safari 14.1+), :has() selector (very new, only in latest browsers), @container queries (still rolling out), position: sticky (quirky in older Safari), scroll-behavior (not supported in older Safari), and clamp() / min() / max() CSS functions (not available in very old browsers). Always check these if you're targeting a broad audience.

Yes! The tool detects whether you've already included vendor-prefixed versions of properties (like -webkit-border-radius or -moz-transition). If a property appears with a prefix, the tool notes this and may adjust the compatibility assessment. However, it's generally better practice to write unprefixed standard CSS and use a build tool like Autoprefixer (with PostCSS) to automatically add the correct prefixes based on your target browser configuration. This keeps your source code clean and maintainable.

We strive to keep the compatibility data current by monitoring the latest stable releases of all major browsers. The database reflects browser versions as of late 2024 / early 2025. For the most critical and rapidly-evolving features (like @container, :has(), and view-timeline), we recommend also checking caniuse.com or MDN Web Docs for the very latest status, as browser updates can ship weekly. Our version baseline selector lets you adjust the target browser age to match your project's support policy.

Absolutely! The tool is designed to handle reasonably large CSS inputs. It parses your entire stylesheet and extracts all unique CSS features for analysis. For very large production files (10,000+ lines), the parsing may take a moment, but the auto-detect feature uses debouncing (0.8-second delay) to avoid excessive re-processing while you type. For the best experience with huge files, we recommend pasting the complete CSS and clicking "Check Now" once. You can also use the filter buttons to focus only on problematic entries, and the Copy Report feature to export findings for your team.