Regenerate Thumbnails, Correctly Sized

No. Choose background regeneration and ThumbPress processes your library through an Action Scheduler queue that keeps running after you leave the page, so large libraries finish without hitting a PHP timeout.

No. Regeneration is failure-safe: if a single image can't be rebuilt, its existing metadata is left untouched rather than wiped, so you never end up with a blank or broken thumbnail.

It rebuilds every size your site currently registers. Sizes you've disabled are cleaned up, and the run reports exactly how many files were created and deleted along with the space saved.

Yes. There is a regenerate button on the individual attachment, so fixing a single wrong crop does not mean reprocessing your entire library.

No. The original file and its URL are untouched - only the generated sizes are rebuilt - so nothing you have already published breaks.

Yes. Cancelling stops the queue cleanly, and images already processed keep their new thumbnails. You can start a fresh run whenever it suits you.

No. Everything is rebuilt on your own server from the original file that is already there, so there is no transfer and no external service involved.

It depends on your server and image sizes, but background regeneration works through the library in batches with live progress, so you can leave it running and check back rather than watching a browser tab.