Browser compatibility refers to whether a web feature (CSS property, JavaScript API, HTML element, etc.) works correctly across different web browsers like Chrome, Firefox, Safari, and Edge. It matters because your website visitors use diverse browsers and devices. If a feature isn't supported on their browser, your site may break or display incorrectly, leading to a poor user experience and potential loss of traffic or revenue.

Use a browser compatibility lookup tool (like this one!) to check the global usage percentage and specific browser version support. As a rule of thumb, features with 95%+ global support are generally safe for production use. For features with lower support, consider using progressive enhancement — provide a fallback experience for unsupported browsers while offering the enhanced feature to modern browsers. You can also use @supports queries in CSS for feature detection.

Progressive enhancement is a design strategy where you start with a baseline experience that works everywhere, then layer on advanced features for browsers that support them. For example, you might use CSS Grid for modern browsers while providing a Flexbox or single-column fallback for older ones. This approach ensures all users can access your content while those with modern browsers get an enhanced experience.

Based on global market share, you should prioritize testing on Google Chrome (desktop + Android), Safari (desktop + iOS), Firefox, and Microsoft Edge. Together these account for over 90% of global browser usage. Also consider Samsung Internet if you have significant mobile traffic from Android users, and Opera for certain international markets.

Partial support means the feature works but with some limitations, bugs, or requires vendor prefixes (like -webkit- or -moz-). For instance, a browser might support the core functionality but not all sub-features, or it may have rendering inconsistencies. When you see partial support, check the detailed notes for that feature to understand the specific limitations before using it.

Browser compatibility data is continuously updated as new browser versions are released (typically every 4-6 weeks for Chrome, Edge, and Firefox). Major browser updates can introduce support for previously unsupported features. We recommend checking compatibility data before starting any new project and periodically reviewing features used in existing projects, especially after major browser releases.

Vendor prefixes are browser-specific prefixes added to CSS properties and APIs during their experimental phase (e.g., -webkit- for Chrome/Safari, -moz- for Firefox, -ms- for Edge/IE). They allow browsers to implement experimental features before they're fully standardized. Today, most modern features no longer require prefixes — but some, like backdrop-filter, still benefit from a -webkit- prefix for broader Safari support. Always check current compatibility data.

The global usage percentage is an estimate based on browser market share data from sources like StatCounter and Can I Use. It represents the approximate percentage of global web users whose browsers support the feature. While not exact, it provides a reliable benchmark for decision-making. A feature with 95%+ global usage is generally considered safe, while anything below 85% may require fallbacks for significant portions of your audience.