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How to Verify if WebP Express is Working on Your Site

22 threads Sep 16, 2025 Plugin → Webp express

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One of the most common questions users have after installing the WebP Express plugin is how to confirm it's actually working. You've configured the settings, but your image URLs still look the same in your browser. This guide will walk you through the steps to verify that WebP images are being served correctly.

Why Verification Can Be Confusing

WebP Express is designed to work seamlessly in the background. In its default "Varied Image Responses" mode, the plugin serves WebP images from the same URL as the original JPEG or PNG. When a supported browser like Chrome requests an image, the plugin delivers the WebP version. An unsupported browser gets the original. This is great for performance and compatibility, but it means you can't simply look at a URL in your browser's developer tools to see if it's a .webp file.

How to Check if WebP Express is Functioning

Method 1: Inspect the Response Headers (Recommended)

The most reliable way to verify the plugin is working is to check the HTTP response headers for an image.

  1. Open your website in Google Chrome.
  2. Right-click on a page and select Inspect to open the Developer Tools.
  3. Go to the Network tab.
  4. Reload the page. You will see a list of all loaded files.
  5. Find and click on an image file (e.g., a .jpg or .png) in the list.
  6. Look at the Headers for that image request.
  7. You should see a header called X-WebP-Convert-Status. A value of Serving freshly converted image or Serving existing converted image confirms WebP Express is working and serving a WebP.
  8. Also, check the Content-Type header. If it says image/webp, you are definitely viewing a WebP image.

Method 2: Use the Built-in Live Test

Newer versions of WebP Express include a "Live Test" feature for its redirection rules.

  1. In your WordPress admin, go to Settings > WebP Express.
  2. Find the Redirection rules section.
  3. Click the Live Test button next to a rule.
  4. The test will run and report whether the redirection to WebP is working correctly for your setup.

Method 3: Third-Party Tools

Tools like Google's PageSpeed Insights often report "Serves images in next-gen formats" as a passed audit when WebP is being successfully served. While this is a good indicator, it's best used in conjunction with checking the headers for definitive proof.

What to Do If You Can't Verify It's Working

  • Check Your Conversion Method: Ensure your chosen conversion method (like GD, Imagick, or a cloud service like EWWW) is configured and working. An invalid API key for EWWW, for example, will prevent conversion.
  • Clear Caches: Clear any server, plugin, or CDN caches (like Cloudflare) that might be serving old, cached versions of your images without the WebP headers.
  • Review the FAQ: The WebP Express team maintains a detailed FAQ that addresses common configuration issues, especially for sites using proxies or CDNs.

By following these steps, you can confidently determine whether the WebP Express plugin is successfully accelerating your website by serving next-generation WebP images.

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