Drop WebP files saved from the web. Each is written as JPEG at matched quality. Transparent WebPs wait for a background colour; animated WebPs are written as their first frame, and the page says so.
Why WebP needs converting
Browsers serve pictures as WebP because it is small, so a picture saved from a web page is often a WebP even when its name says otherwise. Older office software, many upload portals and some photo apps still refuse it. JPEG opens everywhere.
The converter reads the format from the file's bytes, so a WebP named photo.jpg is recognised and converted rather than passed along unchanged.
Animation and transparency
JPEG holds one still picture with no transparency. An animated WebP is written as its first frame, with a note. A transparent WebP is written only after you choose a background colour.
