WebP is an image format introduced by Google in 2010 which combined lossy and lossless compression to deliver images up to 45% smaller than PNGs for similar quality, and of course, fully supported by Google Chrome. It is also supported by Opera and Edge with the October 2018 Update, and now Mozilla is rolling out support for the image format with Firefox 65.
The feature is now available in the Firefox 65 nightly and the bug report noting it as a missing feature is now marked as fixed.
It is notable however that the feature is still off by default, with users needing to activate it by turning on the image.webp.enabled flag.
Via Techdows.com