Why convert images to WebP instead of JPEG or PNG?
WebP typically produces noticeably smaller files than JPEG at the same visual quality, and unlike JPEG it also supports transparency — so it can replace PNG for images that need a transparent background too, at a fraction of PNG's file size. Browser support has been solid for years now, so there's little practical downside to converting website images to it.
Is AVIF better than WebP?
AVIF compresses even smaller than WebP at the same quality, but AVIF encoding is noticeably slower, which matters when converting a large batch or very large images. WebP is the safer default for most batch jobs; reach for AVIF specifically when file size matters more than encoding speed, e.g. a one-time export of hero images for a site that gets a lot of traffic.
Does converting to WebP alone reduce file size enough?
Often not as much as pairing it with other steps. Format conversion changes how pixels are encoded, not how many pixels there are — a 4000px-wide photo converted to WebP is still a 4000px-wide file, just in a more efficient format. For web use, pairing this with the resize tool (down to the dimensions the page actually displays) and the compress tool usually cuts file size far more than format conversion alone.