It helps you decide whether re-generation is necessary after changing image-related settings.
Why You Should Use Thumbnail Re-Generation
Thumbnail re-generation ensures that all generated image versions stay consistent with your current CompressX and WordPress settings.
Over time, image-related settings such as compression quality, output formats (WebP or AVIF), watermark rules, or thumbnail sizes may change. Existing thumbnails are not automatically updated when these settings change.
Running thumbnail re-generation rebuilds previously generated thumbnails so they reflect the latest configuration, without modifying the original uploaded images.
When You Should Use Thumbnail Re-Generation
Thumbnail re-generation is intended to be used after certain settings have changed.
You should run thumbnail re-generation in the following situations:
1. After adding new thumbnail sizes
When a theme or plugin introduces new image sizes, existing images do not automatically have thumbnails generated for those sizes. Re-generation creates the missing thumbnails for previously uploaded images.
2. After changing watermark settings for thumbnails
If thumbnails were previously generated with watermarks enabled and you later disable watermarking, re-generation is required to rebuild clean thumbnail versions without watermarks.
3. When you notice missing JPG or PNG thumbnails
In some cases, certain thumbnails may be missing due to upload issues, interrupted processing, or configuration changes. Running thumbnail re-generation restores missing JPG or PNG thumbnails based on the current settings.
Thumbnail Re-Generation vs Image Optimization
Thumbnail Re-Generation and Image Optimization serve different purposes. The comparison below highlights when to use each.
| Thumbnail Re-Generation | Image Optimization | |
|---|---|---|
| Purpose | Rebuilds the entire thumbnail system based on current settings | Generates modern formats from existing thumbnails |
| Generated Formats | JPG, PNG, WebP, AVIF | WebP, AVIF only |
| Source Images | Original uploaded images | Existing JPG / PNG thumbnails |
| Thumbnail Sizes | Recreates all configured thumbnail sizes | Does not create or change thumbnail sizes |
| Typical Use Case |
After adding new thumbnail sizes, changing watermark rules, or updating image format settings |
After enabling WebP or AVIF for existing images |
In most cases, Image Optimization is sufficient.
Use Thumbnail Re-Generation only when your thumbnail structure or rules have changed.
