Google originally launched the open source WebP format as an alternative to JPEG and PNG on the web.
It has been adopted by Mozilla Firefox and Opera Browser till now. Google Chrome of course already support it.
However, lack of support in Internet Explorer and Apple Safari means that web publishers cannot switch to it without using server hacks to ensure compatibility with everyone.
Google is however continuing the switch on their own platforms. They already use WebP images for previews on search result pages. Google+ also support sharing of WebP images. And now they are using WebP images on Chrome Web Store.
Google developers said:
By converting PNGs and JPEGs to WebP, the Chrome Web Store was able to reduce image sizes by about 30% on average (here’s one sample image in WebP at 8.3kB and JPEG at 32kB). Given the number of requests Chrome Web Store serves, this adds up to several terabytes of savings every day.