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Troubleshooting Common Multisite Issues with Converter for Media

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

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Many WordPress users rely on the 'Converter for Media – Optimize images | Convert WebP & AVIF' plugin to serve next-generation images. However, when used on a Multisite (WPMU) installation, a unique set of challenges can arise. This guide compiles the most common Multisite-related issues and their solutions, based on community reports and troubleshooting.

Common Multisite Problems and Symptoms

Users often encounter the following scenarios when running the plugin on a Multisite network:

  • Plugin only works on the main site: Subsite images return a 404 error or are not converted to WebP, while the main site functions correctly.
  • Configuration and settings access issues: Clicking the plugin's settings menu does nothing or results in a 500 error, especially on Windows/IIS servers.
  • .htaccess file challenges: The required .htaccess rules are not automatically placed in the correct directories (e.g., /wp-content/), or manual edits are overwritten.
  • Non-standard uploads directories: The plugin cannot find images if your Multisite uses a custom file structure, such as /wp-content/blogs.dir/ for site-specific uploads.

Why Do These Multisite Issues Happen?

The core of these problems often lies in the complex file and URL structure of a Multisite network. Unlike a standard WordPress installation, a Multisite can have multiple domains or subdomians pulling media from various physical directories, all managed from a single database. The plugin's default configuration is designed for a standard setup and may not automatically account for these custom paths and server variables.

Recommended Solutions and Workarounds

Based on community feedback, here are the most effective steps to resolve these issues.

1. Manual .htaccess Configuration for Multisite

The plugin's FAQ includes specific instructions for Multisite installations. You will likely need to manually add rules to the .htaccess files in your /wp-content/ and /wp-content/uploads-webpc/ directories. A common mistake is only having a root .htaccess file; you must create them in these subdirectories if they do not exist.

Important: If your host does not populate the %{DOCUMENT_ROOT} variable (a known issue on IONOS), you may need to replace it with the full server path to your WordPress installation in these rules. Be aware that these manual changes can be overwritten if you revisit the plugin's settings page, so this may be a temporary fix.

2. Using Filters for Custom Directories

If your network uses non-standard paths for uploads (e.g., blogs.dir) or you have multiple domains sharing one database but different file directories, the plugin may not detect images correctly. You can use the webpc_supported_source_directory filter to explicitly define the supported source directories for conversion. This requires adding custom code to your theme's functions.php file or a custom plugin.

3. Checking for Nginx Server Configuration

For servers running Nginx, the .htaccess rules are irrelevant. The plugin's FAQ provides a code snippet that must be added to your server's Nginx configuration file. If you are on a Multisite and facing 404 errors on subsites after conversion, it is highly likely the Nginx rules need to be adjusted or applied correctly for all sites in the network. You must contact your hosting provider or server administrator to implement these changes.

4. Network Activation and Individual Settings

The plugin must be network-activated in a Multisite environment. A known limitation is that settings are global across the entire network. There is currently no native support for site-by-site configuration. All sites will share the same conversion settings.

Conclusion

While 'Converter for Media' is compatible with Multisite, its setup is more involved than on a single site. Success typically depends on carefully following the Multisite-specific instructions in the plugin's FAQ, manually verifying server configuration, and potentially using filters for custom directories. If problems persist, checking the plugin's "Help Center" tab for diagnostic information can provide crucial clues for further troubleshooting.

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