WebP in WP: enabling, fallback, and CDN setup
Introduction. This article walks WordPress owners through the practical steps of turning on WebP image support, setting up reliable fallbacks for older browsers, and configuring a content delivery network to serve these assets efficiently. By mastering these techniques you can reduce page weight by 30‑40 %, speed up load times, and improve search rankings—all while keeping your site accessible to every visitor.
Enabling WebP support in WordPress
The first move is to let WordPress generate WebP files automatically when images are uploaded. The built‑in wp_generate_attachment_metadata() hook can be extended with a small snippet that calls the GD or Imagick library to create a WebP copy.
- Add a function in your theme’s functions.php that checks for WebP support and writes the new file into the uploads folder.
- Verify the change by uploading a test image; you should see both JPEG/PNG and WebP files next to each other.
Implementing graceful fallbacks
Once WebP files exist, the site must serve them only when the browser can decode them. Use the <picture> element or a JavaScript polyfill that swaps the srcset based on support detection.
| Item | What it is | Why it matters |
|---|---|---|
| <picture> | HTML element that lists multiple sources. | Browsers pick the first compatible format, ensuring no broken images. |
| WebP support test | JavaScript snippet that sets a class on html. |
Allows CSS to target WebP or fallback images without JS failure. |
| Cache‑busting query strings | Adds a version parameter to image URLs. | Prevents stale files from being served after format changes. |
Configuring a CDN for WebP delivery
A CDN can offload bandwidth and cache the same WebP assets globally. Choose a provider that supports custom headers or automatic content negotiation.
- Upload your WordPress uploads folder to the CDN, preserving the directory structure.
- Set caching rules so that requests for *.webp are served with a long max‑age header while keeping the original MIME type correct.
Common pitfalls and how to avoid them
Many sites fall into a few recurring traps: failing to update image URLs after switching formats, ignoring older browsers that refuse WebP, or misconfiguring CDN cache purges. Address these by:
- Using a plugin that rewrites the
srcsetautomatically when new images are generated. - Testing on Safari and legacy Edge to confirm fallbacks display correctly.
- Scheduling regular CDN purges after major image updates so users always receive the newest files.
Conclusion. By enabling WebP in WordPress, setting up robust fallbacks, and leveraging a CDN, you can slash image sizes without sacrificing compatibility. Start with the simple code snippet, test across browsers, and then scale with your CDN settings—your users and search engines will thank you.
Image by: Markus Winkler
