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Troubleshooting Common WebP Express Plugin Issues: Upload Failures, Settings Resets, and More

25 threads Sep 9, 2025 Plugin → Webp express

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WebP Express is a powerful tool for serving next-generation WebP images on your WordPress site. However, like any complex plugin, users can occasionally run into conflicts and unexpected behavior. Based on community reports, we've compiled a guide to the most common issues and their solutions.

1. Media Upload Failures (Especially from Mobile Apps)

The Problem: Users report that activating WebP Express blocks image uploads, often resulting in timeouts or failures. This is particularly prevalent when using the WordPress mobile app for iOS.

Why It Happens: The plugin's processing hooks into the upload process. On some server configurations or when combined with certain other plugins, this can cause the operation to time out before completion.

Common Solutions:

  • Check for Conflicting Plugins: A common culprit is a security plugin like iThemes Security. Try temporarily disabling other plugins to identify a conflict. If found, check the security plugin's settings for options like "Suspicious Query Strings" and disable them.
  • Server Requirements: Ensure your server meets the plugin's requirements. An outdated PHP version (like 5.6) is a frequent cause of failures. Upgrading to PHP 7.4 or higher has been known to resolve this issue.
  • Conversion Method: If your server's GD library is old, it may struggle with certain image types, causing timeouts. Try switching to a different conversion method (like Imagick) in the WebP Express settings if available.

2. Plugin Settings Randomly Resetting

The Problem: The plugin's configuration reverts to its default factory settings, often after updating a post or due to a WordPress cron event.

Why It Happens: This was a confirmed bug in version 0.17.3 of the plugin.

Common Solutions:

  • Downgrade the Plugin: The most straightforward solution is to roll back to version 0.17.2, which was stable and did not exhibit this behavior. You can download previous versions from the Advanced View on the plugin's WordPress.org page.
  • Update the Plugin: Check if a newer version is available that addresses this bug. The WebP Express team is typically quick to fix such critical issues.

3. PNG Transparency Issues (Black/White Backgrounds)

The Problem: PNG images with transparency are converted to WebP but display with a solid black or white background instead of preserving transparency.

Why It Happens: This is almost always related to using the GD conversion library on an older version of PHP (5.6) or an outdated GD library. GD has known issues with converting palette-based PNGs on older systems.

Common Solutions:

  • Upgrade PHP: Upgrade your server's PHP to version 7.4 or higher. This ships with a newer version of GD that properly handles transparency.
  • Switch Conversion Methods: If your server supports it, switch the conversion method in WebP Express to Imagick or another available converter.
  • Create an Exception: As a last resort, you can create an exception rule in the WebP Express settings to prevent the specific problematic images from being converted.

4. Background Images Not Rewriting (Divi & Other Themes)

The Problem: WebP images serve correctly for standard <img> tags but not for CSS background images defined in themes like Divi.

Why It Happens: The plugin's default HTML parsing method may not be able to find and replace all image URLs within inline CSS styles.

Common Solutions:

  • Change the Alter HTML Method: In the WebP Express settings, navigate to Alter HTML > How to Replace. Change the option from "Using the DOM" to "The complete page (using output buffering)". This more comprehensive method often successfully rewrites background image URLs.

5. Blank Settings Page or Fatal Errors

The Problem: Clicking on the WebP Express settings menu results in a blank white screen or a fatal error.

Why It Happens: This usually indicates missing files or a incomplete/corrupted plugin update.

Common Solutions:

  • Reinstall the Plugin: Completely remove WebP Express and install it fresh from the WordPress repository. This ensures all files are present and correct.
  • Check for Conflicts: Temporarily switch to a default WordPress theme (like Twenty Twenty-Four) and disable all other plugins to see if a conflict is causing the fatal error.

When troubleshooting, always remember to clear your browser, site, and any server-level caches after making changes. If problems persist, the WordPress support forums are a great place to search for your specific error message or seek help from the wider community.

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