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Understanding and Fixing Common Regenerate Thumbnails Issues

48 threads Sep 9, 2025 Plugin → Regenerate thumbnails

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Many WordPress users turn to the Regenerate Thumbnails plugin to fix image display issues after changing themes or adjusting site settings. While powerful, the process can sometimes lead to confusion about where files go, why disk space increases, or how to revert changes. This guide addresses the most frequently asked questions based on community discussions.

Why Do I Have More Images and Less Disk Space After Regenerating?

A significant concern is the sudden increase in server disk usage. This happens because the plugin creates new image sizes for every registered thumbnail dimension set by your WordPress core, active theme, and plugins. If your theme creates 5 sizes and you have a plugin that adds 3 more, each uploaded image will generate 8 additional files. The "Regenerate Thumbnails" process recreates all of these files, which can drastically increase storage consumption, as noted by users who saw backups grow from 700MB to 3.5GB.

How Do I Delete Old, Unused Thumbnails?

The plugin includes an option to clean up unused files. During the regeneration process, you can check the box labeled "Delete thumbnail files for old unregistered sizes in order to free up server space." It is crucial to understand that this only deletes thumbnails for image sizes that are no longer registered on your site (e.g., from a deactivated theme or plugin). Checking this box alone does nothing; you must then click the "Regenerate Thumbnails" button. As it regenerates the new sizes, it will simultaneously remove the files for old, unregistered ones. Be warned: this may cause broken images if those old sizes were hardcoded anywhere.

Can I Undo a Regeneration or Revert to My Original Images?

This is a common point of confusion. The Regenerate Thumbnails plugin does not alter your original, full-size uploaded image. It only creates new, smaller versions (thumbnails) based on that original. If you are unhappy with the new thumbnails, you cannot "undo" the process within the plugin. Your options are:

  • Restore from a Backup: The most reliable method to return your site to its exact previous state is to restore your files and database from a backup created before you ran the regeneration.
  • Manually Re-upload Images: If you do not have a backup, you may need to re-upload the original image files. This will trigger WordPress to generate new thumbnails with your current settings.

Why Are My Images Blurry, Stretched, or the Wrong Color?

The plugin itself does not apply custom filters or quality settings. It relies entirely on WordPress's core image processing libraries (like GD or Imagick). If your new thumbnails are blurry, stretched, or have incorrect colors, the issue likely lies with:

  • Image Size Settings: Check your cropping settings under Settings > Media in your WordPress dashboard. Incorrect aspect ratios or hard crop settings can cause stretching.
  • Theme or Plugin Conflict: Another plugin (e.g., an image optimization tool) or your theme might be overriding the default image generation process or applying its own filters.

Why Can't I Find the Regenerated Images in My Media Library?

The WordPress Media Library primarily displays only the original, uploaded image. The regenerated thumbnails are stored in the same directory on your server (typically /wp-content/uploads/) but are not listed as separate items in the library. You can usually find them by browsing your server via FTP or your hosting file manager. They follow a naming convention like filename-1024x768.jpg.

Key Takeaways

  • Always Backup: Before running a bulk regeneration, ensure you have a recent backup of your site.
  • It Doesn't Change Originals: Your original uploaded images are safe and remain unchanged.
  • Cleanup is Part of the Process: Use the "Delete" option during regeneration to remove old sizes, but be aware of the risks.
  • Check Your Settings: Blurry or stretched images are usually a configuration issue, not a plugin bug.

For more specific issues, like problems with WooCommerce product images or images not updating in posts, reviewing your theme's documentation is highly recommended, as display logic is often theme-dependent.

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