Save a photo from a modern website and, more and more often, what drops into your downloads is a .avif file - and Photos, Photoshop, or your usual viewer just shrugs at it. AVIF is the new image format built on the AV1 codec, and sites reach for it because a photo arrives at about half the size of a JPEG. This AVIF converter turns that file back into plain JPG right on your PC, one image or whole folder at a time.