JPG to WebP

Better compression, same picture

WebP achieves its advantage over JPG by using smarter techniques borrowed from modern video compression. Where JPG independently compresses each small block of the image, WebP additionally predicts what a block will look like based on the blocks already decoded around it, and then stores only the difference between the prediction and reality. Because neighbouring parts of a photograph are usually similar, those differences are small and cheap to record. The result is the same picture in meaningfully fewer bytes. It is a genuine engineering improvement rather than a quality trade — you are not accepting a worse image, you are storing the same image more cleverly.

Watch out for double compression

One caveat deserves attention when converting JPG to WebP. Your JPG is already lossy — detail was discarded when it was created. Encoding it into WebP compresses it a second time, and if you set the quality low, the second round of loss can amplify the artefacts baked in by the first, producing visibly mushy areas. The practical guidance is to keep the quality slider at or near the default, and to convert from the highest-quality JPG you have rather than one that has already been squeezed through an email attachment limit. If you have access to the original camera file, converting from that will always give a cleaner WebP than converting from a heavily compressed copy.