Browser Compatibility and caniuse.com
Check feature support across browsers on caniuse.com, understand vendor prefixes, and use polyfills or fallbacks when needed.
Browser Compatibility and caniuse.com is a free Frontend Academy lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Frontend Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Why Does Compatibility Matter?
Different browsers implement web standards at different speeds. A CSS property or JavaScript API available in Chrome 130 may not exist in an older Safari or Firefox version. Testing and planning for compatibility prevents broken experiences for your users.
caniuse.com — Your Compatibility Reference
Go to caniuse.com and type any CSS property, JavaScript API, or HTML attribute. You'll see a colour-coded support table across all major browsers and their recent versions, along with usage statistics and notes on partial support.
Reading the caniuse Table
Green = supported. Yellow = partial support. Red = not supported. Grey = unknown. Check the global usage percentage at the top — if 97%+ of users have it, you can usually use it without a fallback.
browser-compat-data and MDN
MDN Web Docs pages include a browser compatibility table at the bottom of every API reference page. It uses the same data as caniuse and is updated frequently by browser vendors themselves.
The Baseline Initiative
The Baseline initiative (web.dev/baseline) marks features as Newly Available or Widely Available based on their support across Chrome, Edge, Firefox, and Safari. A Widely Available feature is safe to use without polyfills.
Polyfills
A polyfill is JavaScript code that implements a newer API in older browsers. Popular sources: polyfill.io (deliver only needed polyfills), core-js (comprehensive JavaScript polyfills), Babel helpers.
// polyfill.io example:
<script src="https://polyfill.io/v3/polyfill.min.js?features=Array.prototype.at,Object.hasOwn"></script>@supports — Feature Queries in CSS
@supports lets you write CSS that only applies when a property is supported. Provides CSS fallbacks similar to how media queries provide responsive overrides.
/* Fallback for all browsers */
.grid {
display: flex;
flex-wrap: wrap;
}
/* Enhancement for browsers that support grid */
@supports (display: grid) {
.grid {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
}
}Vendor Prefixes (Legacy)
Older CSS features needed vendor prefixes: -webkit-, -moz-, -ms-. These are mostly obsolete now — modern browsers use unprefixed standard properties. Autoprefixer (PostCSS plugin) adds them automatically if still needed.
Transpilation with Babel
Babel compiles modern JavaScript (ES2022+) down to ES5 that older browsers can run. Vite and webpack integrate Babel via plugins. Configure target browsers in browserslist in package.json.
// package.json
"browserslist": [
"last 2 versions",
"not dead",
"> 0.5%"
]Testing in Real Browsers
DevTools device emulation is not a substitute for real browser testing. Use BrowserStack, Sauce Labs, or the actual Safari browser (requires macOS or iOS) for true cross-browser validation.
The Evergreen Browser Landscape
Chrome, Edge, Firefox, and Safari all auto-update. The long tail of outdated browsers shrinks every year. For most consumer products, targeting the last 2 major versions of each browser covers 95%+ of users.
Quick Check
What does a green cell in the caniuse.com support table indicate?
Recap: Browser Compatibility
Check caniuse.com before using new APIs. Read MDN compat tables. Target sensible browser sets with browserslist. Use @supports for CSS feature queries. Polyfill only what's needed. Transpile modern JS with Babel. Test in real browsers for critical features.
Frequently asked questions
Is the “Browser Compatibility and caniuse.com” lesson free?
Yes — the full text of “Browser Compatibility and caniuse.com” is free to read here on the web, and the Frontend Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Frontend Academy course, upgrade to CoddyKit PRO.
What will I learn in “Browser Compatibility and caniuse.com”?
Check feature support across browsers on caniuse.com, understand vendor prefixes, and use polyfills or fallbacks when needed. You practise Frontend Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Frontend Academy?
No prior experience is required. Frontend Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Browser Compatibility and caniuse.com” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Frontend Academy lesson?
Yes. Every Frontend Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Chrome DevTools: Elements Console Network
- VSCode: Extensions Emmet Shortcuts
- Prettier and ESLint Setup
- Browser Compatibility and caniuse.com