Questions
Does it reduce the quality?
No. Only the metadata is rewritten; the bytes of the image itself are not touched, so nothing is recompressed.
What do the options remove?
Location only removes GPS and place names. Personal info also removes serial numbers, owner and author names, software and editing history, and keeps the date and camera settings. Everything keeps only what the photo needs to display correctly.
Which formats can be cleaned?
JPEG, HEIC/HEIF, AVIF, PNG, WebP and TIFF.
Is my photo uploaded?
No. Cleaning happens in your browser and the cleaned copy is downloaded from there.