WebP: Browser Support, Features, Limitations

What is WebP?

WebP is a raster image format that Google built on top of the VP8 video codec, and the IETF formally specified it as RFC 9649. WebP supports lossy compression, lossless compression, alpha transparency, and animation, ships with the .webp file extension, and uses the image/webp MIME type.

Which browsers does WebP support?

WebP plays in every major desktop and mobile browser today. Internet Explorer is the only modern-era browser that never added support.

What are the key features of WebP?

WebP packs lossy, lossless, animation, and alpha transparency into a single format, with file sizes smaller than JPEG, PNG, and GIF at matching picture quality.

• Lossy compression: WebP files are 25 to 34 percent smaller than JPEG at the same quality, based on Google's reference encoder tests on the Kodak photo set.
• Lossless compression: WebP lossless files are about 26 percent smaller than equivalent PNG files, with full alpha transparency.
• Alpha transparency: Both lossy and lossless WebP carry an 8-bit alpha channel, so designers no longer need a separate PNG to keep transparency on photos.
• Animation: Animated WebP replaces GIF and APNG, with full 24-bit color, alpha, and frame timing inside a single .webp file.
• ICC, EXIF, and XMP metadata: WebP carries color profile, camera, and copyright metadata, so it slots into existing photo pipelines without a transcode step.
• Royalty-free license: Google publishes libwebp under a BSD-style license and the WebP bitstream itself carries no patent fees, so encoders and decoders ship without per-unit costs.
• Maximum dimensions of 16383 x 16383 pixels: WebP supports images up to 16383 by 16383 pixels, which covers all responsive web use cases except print-grade gigapixel scans.

How do you check if a browser supports WebP?

WebP support varies across older browser builds, so production sites need a runtime check before serving a WebP source. The cleanest detection probes the browser's image decoder rather than parsing the user agent string.

• Open DevTools: Open the page in the browser you want to test and press F12 (or Cmd+Option+I on macOS). Switch to the Console tab.
• Paste the feature-detection snippet: Run the JavaScript below. It loads a 2x1 WebP buffer through the Image() API and reports whether the browser decoded it.
• Read the result: A true value means WebP works in this browser; false means you need to ship a JPEG or PNG fallback.
• Wire a picture element fallback in HTML: Wrap your image in a picture tag with a WebP source and a JPEG or PNG img child. The browser picks the first format it can decode, with no JavaScript required.
• Verify on real browsers and OS: Cross-check the result on Chrome, Edge, Firefox, Safari 14, Safari 16, the legacy Android Browser, and any Internet Explorer traffic still in your audience.

function supportsWebP(callback) {
  const img = new Image();
  img.onload = () => callback(img.width === 2 && img.height === 1);
  img.onerror = () => callback(false);
  img.src =
    "data:image/webp;base64,UklGRhoAAABXRUJQVlA4TA0AAAAvAAAAEAcQERGIiP4HAA==";
}

supportsWebP((isSupported) => {
  console.log("WebP supported:", isSupported);
});

If the snippet logs false on a browser you expect to support WebP, check that the data URL was not blocked by a Content Security Policy directive that restricts img-src to https only.

What are the known issues with WebP?

WebP is supported in every major browser, but real-world delivery still has rough edges around legacy browsers, animated playback, and editor tooling.

• No Internet Explorer support: IE 5.5 through IE 11 cannot decode WebP in any context. Sites that still target enterprise IE fleets need a JPEG, PNG, or GIF fallback inside a picture source list.
• Safari quirks before macOS Ventura: Safari 14 to 15.6 plays most lossy WebP images, but drops frames on animated WebP and renders some lossless WebP files as a static keyframe. Safari 16 fixed both gaps, so users still on Big Sur or Monterey hit this regularly.
• Animated WebP is not always smaller: Animated WebP beats GIF on file size, but it can fall behind animated AVIF and even short MP4 clips for loops longer than a few seconds. Profile your clips before swapping formats.
• Older Android Browser gaps: Android 4 to 4.1 played only lossy WebP, and Android 2.1 to 3 had no support. Use Chrome for Android, Firefox for Android, or Samsung Internet on modern phones to avoid the legacy stock browser.
• Image editor friction: Adobe Photoshop needs version 23.2 or later for native WebP, and many older Windows editors still require the WebP codec pack. Designer hand-offs often arrive as PNG until the editor is updated.
• Email client coverage is patchy: Apple Mail, Gmail, and Outlook for Microsoft 365 render WebP, but legacy desktop Outlook builds and several embedded webview clients still need a fallback. Test campaigns with Litmus or Email on Acid before sending.
• Default download behavior on older Windows builds: Windows 8.1 and the original Windows 10 (build 17763 and earlier) treat WebP as a download instead of opening it in the Photos app. Users on those builds need the WebP Image Extensions package from the Microsoft Store.

In my experience, the most common production failure is shipping animated WebP without a poster fallback to Safari 14 and 15 users, who see a frozen first frame instead of the loop. Always pair animated WebP with a JPEG or PNG poster and a sensible HTML fallback inside picture, then probe canPlayType-style detection at runtime.

Citations

All WebP version numbers and platform notes in this guide come from these primary sources:

• IETF RFC 9649 - WebP Image Format: datatracker.ietf.org/doc/html/rfc9649
• Google Developers - WebP FAQ: developers.google.com/speed/webp/faq
• Google Developers - An image format for the Web: developers.google.com/speed/webp
• MDN Web Docs - Image file type and format guide: developer.mozilla.org/en-US/docs/Web/Media/Guides/Formats/Image_types
• Wikipedia - WebP: en.wikipedia.org/wiki/WebP
• WebKit - New WebKit Features in Safari 14: webkit.org/blog/11340/new-webkit-features-in-safari-14
• Apple Developer - Safari 14 Release Notes: developer.apple.com/documentation/safari-release-notes/safari-14-release-notes
• Mozilla - Firefox 65 Release Notes: mozilla.org/en-US/firefox/65.0/releasenotes
• Microsoft Apps - WebP Image Extensions: apps.microsoft.com/detail/9pg2dk419drg
• Mozilla Hacks - Firefox 65: WebP support: hacks.mozilla.org/2019/01/firefox-65-webp-flexbox-inspector-new-tooling