WebP is the new image format for the web. Google is working on the project.
Here is the comparison of the image with optimized image format (PNG). Currently png format is considered optimized one for web. But the new image format WebP is reducing the size by 25 percent. If you are ready to loose some more then the saving is by 75%-80% and it is very very good as the last image is nothing very different than the first one. It can greatly enhance the speed of web and save bandwidth as well.
PNG file size: 118.5 KB
WebP-lossless file size: 88.1 KB
WebP-lossy (with alpha) file size: 23.4 KB
As WebP image format is not supported in web browsers, so the webP images are converted back to PNG for displaying on web page. Google has made software for converting the image from png and other image format (jpeg etc) to webP available on their site to download free of cost with details information of the image format.