The new size is missing.
A card layout needs a thumbnail that earlier uploads never had. Generate the missing file variants for the existing library.
WordPress image sizes & regeneration
New layout. Right image sizes.
Define the dimensions your layouts need, decide which thumbnails get generated, and bring existing images into line with MediaToolkit.
Built with love for
- Custom dimensions and crop settings
- Generate missing thumbnails
- Rebuild selected image variants
When the layout changes
Your older uploads did not get the memo.
Changing an image-size definition and producing the files are two separate jobs.
The old settings keep producing files.
Review the sizes registered by WordPress, your theme, and plugins. Decide which sizes should be generated going forward.
The current crop matters.
A rebuild should consider the framing you already chose. Reuse valid saved MediaToolkit crop recipes when regenerating.
Your size-management workflow
Define the size. Choose the work. Run the rebuild.
Separate a change to your settings from a deliberate change to existing images.
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Review and define image sizes.
See registered sizes and add your own dimensions, names, and crop settings. Existing core, theme, and plugin definitions remain under their original owner.
Custom Image Sizes
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Pick missing-only or regeneration.
Generate missing thumbnails when you want to fill gaps and preserve existing files. Choose regeneration when the selected variants need rebuilding.
Regenerate Thumbnails
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Follow the bulk job.
Run the image work through a saved job with progress, pause and resume controls, and a job history. Review the results and any image-specific errors.
Bulk Processing
Saving a size definition or disabling future generation does not itself rewrite or delete existing files. Run regeneration explicitly when you need new variants.
In practice
Useful after a redesign. Useful long after launch.
Size management is an ongoing part of maintaining the image library.
Add the card size your redesign needs.
Define the dimensions for a new card treatment, then generate the missing thumbnails for older images. Existing thumbnail files stay unchanged in missing-only mode, so the job can focus on the gaps introduced by the new size.
Confirm the definition before the job.
Check the intended width, height, and crop setting before generating the new size across older images. A correctly named size with the wrong dimensions still produces the wrong result; inspect a representative image and placement first.
Rebuild with your crop decisions in mind.
When a selected size needs regenerating, MediaToolkit checks its saved crop and focal-point recipes. Valid recipes can be reused. If the source or size definition has changed, inspect the result rather than assuming an old frame will still fit.
Review the result at its actual placement.
Open the rebuilt image where the site uses it, especially after a theme or layout change. Compare the framing and visible detail at the required dimensions, then adjust the source or crop when the new placement demands it.
A few useful answers
Before you start
Does adding a custom size change my existing images?
No. Saving a definition registers that size for future use. Existing images need an explicit missing-thumbnail or regeneration operation to receive the corresponding files.
What is the difference between missing-only and regeneration?
Missing-only creates absent thumbnails while keeping existing thumbnail files. Regeneration rebuilds the selected variants according to the current definitions and applicable saved recipes.
Can I edit a size registered by my theme?
You can inspect registered sizes, but MediaToolkit does not overwrite definitions owned by WordPress, themes, or other plugins. Create and manage your own custom sizes.
Will regeneration preserve every crop?
It can reuse valid saved MediaToolkit crop and focal-point recipes. It cannot reconstruct arbitrary third-party crops or promise identical output after relevant source or size changes.
Does disabling a size remove its old files?
No. Generation controls affect future file creation. Existing files remain in place; this is not a media cleanup or unused-image deletion tool.
Related workflows: Thumbnail cropping · WordPress Multisite settings.
Yearly plans for ongoing image-size maintenance.