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Why Are Some Images Still JPG? Troubleshooting WebP Display Issues

16 threads Sep 16, 2025 Plugin → Converter for media – optimize images | convert webp & avif

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You've installed the 'Converter for Media – Optimize images | Convert WebP & AVIF' plugin, your server meets all the requirements, and the bulk conversion says it's 100% complete. Yet, when you check your site, some images stubbornly remain in their original JPG or PNG format. This is a common point of confusion and frustration for users.

Based on community reports and troubleshooting threads, here are the most common reasons why this happens and how to resolve them.

1. Server or Browser Cache

This is by far the most frequent culprit. Your server, a caching plugin, or even your own browser might be serving a saved version of the page that still references the original images.

How to fix it:

  • Clear all caches: Purge your server-level cache (if you have one), your WordPress caching plugin's cache, and any CDN cache.
  • Hard refresh your browser: Use Ctrl+F5 (Windows) or Cmd+Shift+R (Mac) to bypass your local browser cache.
  • Wait: Some server caches are configured to refresh on a schedule. If you recently converted the images, wait a few hours and check again.

2. File Permission Issues

The plugin needs read and write access to your files. If your server's file permissions are too restrictive, the plugin may successfully convert an image but then be unable to read it later to serve the WebP version, resulting in a fallback to the original.

How to fix it:

  • Ensure the wp-content/uploads/ and wp-content/uploads-webpc/ directories (and all files within them) have the correct read/write permissions. Typically, directories should be 755 and files should be 644. Your web host's support team can help you verify and correct this.

3. External or CDN-Hosted Images

The plugin can only convert and serve images that are physically located on your server. If your images are being pulled from an external URL or a CDN that you haven't configured in the plugin's settings, they will not be converted.

How to fix it:

  • Verify that the images in question are hosted on your server. Check the image's URL in your browser's developer tools (Network tab). If the domain is different from your website's, that is the issue.
  • If you use a CDN, consult the plugin's documentation for any required configuration to ensure compatibility.

4. The 'Larger Than Original' Setting

The plugin has a smart feature enabled by default: "Automatic removal of files in output formats larger than original". If a converted WebP file ends up being larger than the original JPG/PNG (which can happen with certain images), the plugin will automatically delete the WebP version to avoid hurting your site's performance. The original image will remain.

How to fix it:

  • You can uncheck this option in the plugin's settings. This will force the plugin to keep all converted WebP files, regardless of their size. Be aware that this may slightly increase overall page load size for those specific images.

5. How to Confirm It's Working

Before troubleshooting deeply, confirm the plugin is actually active for some images. The easiest way is to use your browser's Developer Tools:

  1. Right-click on a page and select Inspect.
  2. Go to the Network tab and check the Disable cache box.
  3. Reload the page.
  4. In the list of loaded files, filter by Img.
  5. Click on an image request. In the headers panel, look for the Content-Type header. If it says image/webp, that image is being served correctly. If it says image/jpeg or image/png, that image is falling back to the original format for one of the reasons above.

By methodically working through these common issues, you should be able to get your WebP images displaying correctly and start benefiting from the faster load times.

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