The practical differences
JPEG is a mature lossy photo format with broad support across browsers, operating systems, cameras and editing software. It has no transparency. WebP supports lossy and lossless images and an alpha channel, and browsers can often decode it efficiently.
A WebP may be smaller than a JPEG at a similar visual quality, but this is not guaranteed for every encoder, image or setting. Compare files at the same pixel dimensions and judge visible quality at the size people will see them.
Which one should you use?
Choose WebP for modern web delivery when your supported browsers handle it and you want one format for photos and transparent artwork. Choose JPEG when compatibility with older software or existing workflows matters more than alpha support.
Neither extension makes a poor source image better. Save an original master before lossy conversion, and do not convert back and forth as an editing workflow.
Frequently asked questions
Does WebP replace JPEG everywhere?
No. WebP is widely supported on the web, while JPEG still has broader support across older tools and workflows.