Safari 14 only supports webp in Big Sur. If you want that "update" you have to upgrade OSX. Sometimes it's version number, sometimes like in this case it's just

Safari 14 only supports webp in Big Sur. If you want that "update" you have to upgrade OSX. Sometimes it's version number, sometimes like in this case it's just the feature. From a browser compatibility perspective though it's not much different. We are waiting on lagging support for certain browser features because Apple is gating them behind OSX upgrades.