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Regenerate Thumbnails

Regenerate all image thumbnail sizes across your media library. Essential after switching themes, changing image dimensions, or adding new custom sizes.

Use Cases

  • Fix broken or improperly sized images after switching themes
  • Recreate missing thumbnails after server migration
  • Generate thumbnails for newly added custom image sizes

How It Works

  1. View all registered image sizes in the settings panel
  2. Click “Start Regenerating” to begin the process
  3. Watch real-time progress as each image is processed
  4. All thumbnail sizes are recreated from originals

Where to Find It

Access via Switchboard → Media → Regenerate Thumbnails. The interface shows your current image sizes and regeneration controls.

Before You Start

The settings panel displays:

Image Count

Total number of images in your media library that will be processed.

Registered Image Sizes

A complete list of all image sizes that will be generated:

TypeDescription
WordPress DefaultThumbnail, Medium, Medium Large, Large
Theme/PluginSizes registered by your theme or plugins
Custom (Switchboard)Sizes you created with Custom Image Sizes module

Review this list to understand what sizes will be regenerated.

Running Regeneration

  1. Click “Start Regenerating”
  2. Confirm the action in the dialog
  3. Watch the progress bar fill as images process
  4. View the activity log for real-time status

Progress Display

  • Progress bar — Visual percentage complete
  • Counter — “45 / 500” style count
  • Current image — Name of the image being processed
  • Activity log — Timestamped success/failure for each image

Stopping Mid-Process

Click “Stop” to halt regeneration. If you restart later, the process begins from the first image again.

Don’t navigate away during regeneration. A warning will appear if you try to leave the page while processing is active.

Processing Time

Regeneration time depends on:

FactorImpact
Number of imagesMore images = more time
Number of sizesMore sizes per image = more time
Server speedFaster server = faster processing
Image dimensionsLarger originals take longer

Rough estimates:

  • 100 images: 1-2 minutes
  • 500 images: 5-10 minutes
  • 1000+ images: 15-30+ minutes

What Happens During Regeneration

For each image:

  1. Old thumbnail files are deleted
  2. Original image is loaded
  3. All registered sizes are generated fresh
  4. Attachment metadata is updated

Activity Log

The log shows real-time results:

[10:23:45] ✓ product-photo-001.jpg
[10:23:46] ✓ hero-banner.png
[10:23:47] ✗ Failed: corrupt-image.jpg
[10:23:48] ✓ team-headshot.jpg

Green checkmarks indicate success. Red X marks indicate failures (usually corrupt or missing files).

After Regeneration

Once complete:

  • All images have fresh thumbnails at all registered sizes
  • New custom sizes are available for all existing images
  • Any theme-required sizes are properly generated
  • Metadata is updated to reflect new file information

When to Regenerate

ScenarioRegenerate?
Switched themesYes
Changed Settings → Media dimensionsYes
Added custom image sizesYes
Installed image optimization pluginUsually yes
Normal content editingNo
Uploaded new imagesNo (handled automatically)

FAQ

Will this affect my original images?No. Only thumbnails are regenerated. Your original uploaded files remain untouched. Thumbnails are recreated from the originals.
What if regeneration fails for some images?The log shows which images failed. Common causes: missing original file, corrupt image, or insufficient memory. Failed images can usually be re-uploaded individually.
Can I regenerate just one image?This module processes all images. To regenerate a single image, use the Media Replacement module to replace it with itself, or re-upload the original.
Will this increase disk usage?It might slightly. If you added new image sizes, more thumbnails means more disk space. If you removed sizes, space usage might decrease after regeneration.
Does this work with WebP images?Yes. WebP images generate thumbnails just like JPEG/PNG. If you have the WebP Conversion module enabled, new thumbnails will also be in WebP format.
My page timed out during regeneration. What now?Regeneration happens via AJAX, so browser timeouts shouldn’t stop it. If you experience issues, try reducing server load and restart. Note that restarting begins from the first image again.
Do I need to clear caches after?It’s a good idea to clear any caching plugin caches and CDN caches after regeneration to ensure visitors see the new images.
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