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Why Aren't My WebP Images Showing? Common Issues and How to Fix Them

32 threads Sep 16, 2025 Plugin → Webp express

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If you've installed the WebP Express plugin and your images aren't displaying as expected, you're not alone. This is a common point of confusion that can stem from a variety of configuration and environmental factors. This guide will walk you through the most frequent reasons WebP images might not be served and how to resolve them.

1. Check if WebP is Actually Being Served

Before troubleshooting, confirm whether the issue is real. A file ending in .jpg can still be a WebP image! Browsers determine the file type by its MIME type, not its extension.

How to check:

  • Open your browser's Developer Tools (F12).
  • Go to the Network tab and reload the page.
  • Filter for Img requests.
  • Click on an image request and look at the Headers tab. Under Response Headers, look for content-type: image/webp. If you see this, the image is being served as WebP, even if the URL ends in .jpg.

2. Clear All Caches

Caching is the number one culprit for images not updating. This includes:

  • Browser Cache: Clear your browser cache or test in an incognito/private window.
  • WordPress Cache: Clear any caching from plugins like WP Super Cache, W3 Total Cache, or LiteSpeed Cache.
  • CDN Cache: If you use a Content Delivery Network (CDN) like KeyCDN, BunnyCDN, or Cloudflare, you must purge its cache for changes to take effect. Thread 8 highlights a user who resolved their issue by purging BunnyCDN.

3. Configure Your CDN Correctly

CDNs can interfere with WebP delivery. WebP Express has two primary operation modes, and choosing the right one for your CDN is critical.

  • Varied Image Responses: This mode serves WebP or JPEG from the same URL, depending on the browser. Most CDNs do not support this by default as they cache the first response (e.g., a WebP) and serve it to all visitors (e.g., IE users), breaking the site. If you use a CDN, you likely need to use the other mode.
  • CDN Friendly / Varied Image URLs: This mode serves WebP images on a different URL (often ending in .jpg.webp). This is the recommended mode for CDN users as it avoids caching issues. You can find this setting in WebP Express > Settings > General > Operation mode.

4. Alter HTML Settings

For WebP Express to replace image tags in your content, the Alter HTML feature must be configured correctly. If your theme uses specific functions to output images (like get_the_post_thumbnail()), you may need to adjust these settings.

What to check:

  • Ensure Alter HTML is enabled in the settings.
  • Experiment with the How to replace option. Try switching between Replace image URLs and Replace <img> tags with <picture> tags.
  • Experiment with the Scope option. Try using Use content filtering hooks (the_content, the_excerpt, etc) or The complete page (using output buffering).

As seen in Thread 12, trying different Alter HTML options can resolve display issues like a repeating logo.

5. Social Media and Open Graph (og:image) Issues

Social media platforms like Facebook often do not support WebP images for previews. If you share a post, the preview image may be broken.

Solution: The WebP Express team suggests disabling WebP conversion for images used by social media plugins. You can do this by adding a rule in the Scope section of the Alter HTML settings to exclude images with a specific class or size often used by social meta tags (e.g., og:image). You may need to consult your social media plugin's documentation to identify the right image attributes to exclude.

6. Conversion Failures

Sometimes, individual images fail to convert. This can be due to corrupt source files, file permissions, or problems with the image converter (Gd or Cwebp).

How to troubleshoot:

  • Run a Bulk Convert again. It will only attempt to convert images that are missing a WebP version.
  • Check the conversion logs. WebP Express creates detailed logs for failed conversions in wp-content/webp-express/log/conversions/. The log may indicate why a specific image failed.
  • Check the error message in your WordPress admin or server error logs. For example, Thread 16 shows an error (Not a JPEG file) that indicates the plugin tried to convert a file that wasn't a valid image.

7. Browser Compatibility and .htaccess

WebP Express uses .htaccess rules to redirect image requests. If these rules are not working, WebP images won't be served.

  • Old Browsers: The plugin should not serve WebP to incompatible browsers (like IE11 or old Edge). If it does, check your operation mode is not Varied Image Responses while using a CDN (see point 3).
  • Nginx Users: If your server runs Nginx, you must manually add the rewrite rules to your server configuration, as it cannot read .htaccess files. The plugin provides these rules in its FAQ.
  • Server Paths: Thread 23 shows errors where the plugin could not find the cwebp binary because it was looking in the wrong path. Ensure your server's path to tools like cwebp is correctly configured in the converter settings.

By methodically working through these common issues, you can almost always identify and fix why your WebP images aren't showing. Start by confirming the images are truly not being served as WebP, then move down the list, checking caches, CDN configuration, and plugin settings.

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