I don’t know what a .webp file is but I don’t like it. They’re like a filthy prank version of the image/gif you’re looking for. They make you jump through all these hoops to find the original versions of the files that you can actually do anything with.
WebP can be lossless or lossy compression. However, it is not easily apparent which compression mode is used for a given WebP file.
Google says lossy WebP is 25 percent smaller than JPEG and lossless WebP is 25 percent smaller than PNG.