Automatically converts your JPEG and PNG uploads into Google’s WebP format. This plugin reduces image file sizes by up to 80% without sacrificing visual quality.

Simple WebP Optimizer

Auto-convert JPG/PNG to WebP. Save up to 80% server space and boost site speed with built-in bulk optimization and real-time savings reports.

Francesco Sganga

Optimize images (jpg, png) in your WordPress site by converting them to .webp extension (it uses PHP GD library) 
WP Media Optimizer (.webp) only works with Firefox and Chrome (at this time).
— SAFARI NOW SUPPORTS .WEBP images —
Now with LAZY LOAD FEATURE!
IMPORTANT: WPMOWEBP works only in the frontend side of your website (e.g. not in wp-admin/)
ABOVE THE FOLD Feature is not really “for dummies” but with some tests you can really improve your PAGE SPEED RATE! Hope you can appreciate this feature.
USAGE
Simply install and activate it, and your images will be optimized.
You can send a Feature Request from the Plugin Settings Page. 
I hope you will use this form so I can add new features to this simple and wonderfurl plugin!
You can enable the new Lazy Load Feature by making a little donation to the author, you will receive a life time token for this feature and future improvements.
HOW IT WORKS
When anyone access to a WordPress page, plugin check for images already converted to .webp. 
If one or more images have not been already converted, the plugin converts them immediately. 
Converted images are stored in a subfolder of wp-content folder: wp-content/wpmowebp
TROUBLESHOOTING
If WordPress go out of memory try to add 
define(‘WP_MEMORY_LIMIT’, ‘256M’); 
to your wp-config.php
Enjoy your new WordPress Plugin.

WP Media Optimizer (.webp)

Automatically optimize images in your Wordpress site by converting them to .webp extension

Simple WebP Optimizer vs WP Media Optimizer (.webp)