By Shad Super in Questions —

What Are the Compatibility Considerations for Using WebP Images Across Different Browsers, and How Can You Ensure Fallback Solutions for Unsupported Browsers?

Summary

WebP image format offers superior compression and quality, benefitting web performance. However, browser compatibility varies. Ensuring fallback solutions for unsupported browsers involves using suitable HTML/CSS techniques or JavaScript to dynamically serve alternative formats like JPEG or PNG.

WebP Browser Compatibility

WebP, developed by Google, provides both lossless and lossy compression, making it attractive for web developers. However, compatibility issues necessitate fallback solutions for browsers that do not support WebP.

Supported Browsers

As of 2023, the following browsers support WebP:

  • Google Chrome (from version 32)
  • Firefox (from version 65)
  • Microsoft Edge (from version 18)
  • Opera (from version 19)
  • Safari (from version 14)

For a detailed and updated list of supported browsers, visit Can I use WebP.

Unsupported Browsers

Older versions of browsers and some niche browsers may not support WebP. Notably, Internet Explorer does not support WebP, and earlier versions of Safari (before 14). For these cases, fallback solutions are essential.

HTML Fallback Solutions

To serve fallback images for unsupported browsers, use the HTML <picture> element or <img> with the srcset attribute.

Using the <picture> Element

The <picture> element allows specifying multiple sources for a single image:

<picture>
  <source srcset="image.webp" type="image/webp">
  <source srcset="image.jpg" type="image/jpeg">
  <img src="image.jpg" alt="Descriptive Text">
</picture>

Here, the browser will try to use the WebP image first. If WebP is not supported, it will fall back to JPEG.

Using the <img> Element with srcset

The <img> element with srcset attribute provides a simple alternative:

<img src="image.jpg"
     srcset="image.webp 1x, image.jpg 2x"
     alt="Descriptive Text">

In this approach, srcset instructs the browser to use the WebP image if supported, otherwise, it defaults to JPEG.

CSS Fallback Solutions

Using CSS background-image

Implementing fallback for background images in CSS:

.background {
  background-image: url('image.jpg');
  background-image: -webkit-image-set(url('image.webp') 1x, url('image.jpg') 2x);
  background-image: image-set(url('image.webp') 1x, url('image.jpg') 2x);
}

This CSS snippet ensures that WebP is utilized if supported, otherwise, it falls back to JPEG.

JavaScript Solutions

JavaScript can dynamically check for WebP support and serve the corresponding image format:

<script>
function supportsWebP(callback) {
  var webP = new Image();
  webP.onload = webP.onerror = function () {
    callback(webP.height === 2);
  };
  webP.src = "data:image/webp;base64,UklGRhYAAABXRUJQVlA4TAAAAABwA..."
}
supportsWebP(function (supported) {
  var img = document.getElementById('dynamic-img');
  img.src = supported ? 'image.webp' : 'image.jpg';
});
</script>

This script tests WebP support and sets the image source accordingly.

Conclusion

While WebP significantly enhances image compression and quality, ensuring compatibility across different browsers is essential. Using HTML elements like <picture> and <img> with srcset, CSS background images, and JavaScript, developers can implement effective fallback solutions for unsupported browsers.

References