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Troubleshooting Common Issues with Force Regenerate Thumbnails

35 threads Sep 16, 2025 Plugin → Force regenerate thumbnails

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Why Your Thumbnails Might Break After Regeneration (And How to Fix It)

A powerful tool for managing your site's images, the 'Force Regenerate Thumbnails' plugin is a favorite among WordPress users. However, like any tool, it can sometimes have unintended consequences if not used with a full understanding of its function. A common and distressing issue reported by users is that after regenerating thumbnails, images embedded in old posts appear broken. This article explains why this happens and provides the most effective solutions to get your site back on track.

Understanding the Core Issue: Hard-Coded Image Paths

The primary function of the 'Force Regenerate Thumbnails' plugin is to delete all existing image sizes for your uploaded images and then recreate them based on your current theme's and WordPress's thumbnail settings. The problem arises when old posts or pages on your site link directly to a specific image size.

For example, an old post might contain an image with a source URL like:
yoursite.com/wp-content/uploads/2012/08/My-Image-520x390.jpg

When you run the plugin, it first deletes that specific 520x390 version of the image. It then creates new image sizes based on your current settings. If your current theme no longer uses a 520x390 size, that file is never recreated. The link in your old post now points to a file that no longer exists, resulting in a broken image.

How to Fix Broken Image Links

If you find yourself in this situation, don't panic. The solution involves tricking WordPress into recreating the missing image sizes.

Solution 1: Recreate the Old Image Size in Your Theme

This is the most common and recommended fix. You can manually add the missing image size back to your theme's functions.php file.

  1. Access your WordPress files via FTP or your hosting provider's file manager.
  2. Navigate to your theme's folder and open the functions.php file for editing.
  3. Add the following line of code, replacing the dimensions with the ones you need (e.g., 520x390): 
    add_image_size( 'old-size', 520, 390, true ); // True parameter enables hard cropping
  4. Save the file and upload it back to your server.
  5. Return to your WordPress admin dashboard and run the 'Force Regenerate Thumbnails' process again. The plugin will now create the old image size you just defined, fixing the broken links in your posts.

Important Note: Always use a child theme when modifying theme files to prevent your changes from being overwritten during a theme update.

Best Practices to Avoid Problems in the Future

  • Avoid Hard-Coding Image URLs: Whenever possible, use WordPress functions like the_post_thumbnail() or wp_get_attachment_image() to display images. These functions automatically retrieve the correct image URL, preventing broken links if sizes change later.
  • Add New Sizes, Don't Change Old Ones: If you are changing your theme's design and need new image dimensions, add them as new, uniquely named sizes in your functions.php instead of modifying the dimensions of existing ones. This preserves all the old image files.
  • Always Backup: Before performing any major operation like regenerating thousands of thumbnails, it is highly advisable to take a full backup of your site's files and database.

Other Common Questions

Does the plugin work on WordPress Multisite installations?

Based on community feedback, the plugin appears to be compatible with WordPress Multisite. However, as with any plugin, it is recommended to test it on a staging site first.

Where is the bulk action option?

If you don't see the option to regenerate thumbnails for specific images, ensure you are in the Media Library's List view, not the Grid view. In List view, you can check multiple images and select 'Force Regenerate Thumbnails' from the Bulk Actions dropdown menu.

By understanding what the plugin does and following these best practices, you can effectively manage your site's images without the fear of breaking your content.

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