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Why Your WebP Images Aren't Showing: Common Issues and How to Fix Them

68 threads Sep 10, 2025 Plugin → Ewww image optimizer

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Getting WebP images to display correctly across your WordPress site can be a common point of frustration. Based on community discussions, here are the most frequent reasons WebP delivery fails and the steps you can take to resolve them.

1. WebP Images Haven't Been Generated

This is the most fundamental step. Enabling the 'JPG/PNG to WebP' option alone is not enough. You must run a Bulk Optimize operation from the EWWW Image Optimizer admin panel to create WebP versions of your existing media library images. For new uploads, the conversion should happen automatically.

2. Incorrect WebP Rewriting Method for Your Setup

Choosing the right delivery method is critical. The plugin offers several, but they are not all compatible with every hosting environment.

  • .htaccess Rules: This is often the most efficient method but will NOT work if your site is behind a proxy or caching service like Cloudflare, Sucuri, or most CDNs. These services intercept requests before they reach your server's .htaccess file.
  • JS WebP Rewriting: This is the recommended alternative for sites using a CDN or proxy. It uses JavaScript to detect browser support and swap image sources. A known limitation is that it may not work on images loaded dynamically into the DOM after the initial page load (e.g., via AJAX or 'Load More' buttons) without custom implementation.
  • Picture WebP Rewriting: This method wraps images in <picture> tags. It can also be incompatible with certain themes or page builders that handle images in a non-standard way.

3. Conflicts with Lazy Loading and AJAX

Many themes and plugins use lazy loading to improve performance. If images are loaded as a user scrolls (via AJAX), the WebP rewriting script may not detect them. As seen in the threads, disabling a theme's 'load images on scroll' feature can instantly resolve this. Similarly, content loaded by AJAX calls (like infinite scroll) may not trigger the WebP script, requiring a custom JavaScript solution to re-initialize it.

4. Non-Standard HTML Attributes

Page builders and plugins sometimes store image URLs in custom data attributes like data-lazy-src instead of the standard src. The WebP rewriting scripts are designed to look for standard attributes and may miss these. If your images are using non-standard attributes, the scripts may need to be extended for full compatibility.

5. How to Verify WebP is Actually Working

Don't rely on the file extension in the page source! Due to transparent conversion methods, an image URL might end in .jpg but the browser could actually be receiving a WebP file.

To truly verify:

  1. Open your browser's Developer Tools (F12).
  2. Go to the Network tab.
  3. Reload the page.
  4. Look at the list of loaded files and find an image. The Type column will show its true MIME type. A successfully delivered WebP image will show as webp.

6. Browser Support and Fallbacks

A key advantage of EWWW Image Optimizer's methods is that they include built-in fallbacks for browsers that do not support WebP (like older versions of Safari, Firefox, and Internet Explorer). The server or JS script detects browser support and only serves WebP to compatible clients, serving the original JPEG or PNG to others. If some images work and others don't, the issue is likely delivery, not browser support.

Summary: A Basic Troubleshooting Checklist

  1. Ensure you have run a Bulk Optimize to generate WebP files.
  2. If you use Cloudflare or another CDN, avoid the .htaccess method. Use JS WebP Rewriting instead.
  3. Clear all caching layers: your WordPress cache, any server-level cache, and your CDN's cache.
  4. Temporarily disable lazy loading to see if it is causing a conflict.
  5. Use your browser's Network tab to verify the images are being served with the webp MIME type.
  6. Check if the issue is specific to a theme or page builder. Switch to a default WordPress theme (like Twenty Twenty-Three) momentarily to test.

By methodically working through these common issues, you can successfully configure EWWW Image Optimizer to deliver next-generation WebP images to your visitors.

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