Being one of many great image optimizing plugins for WordPress, EWW Image Optimizer stands out as it handles image compression locally on the host, not requiring an API or licence key to an online image compression service (although that is a premium option). It also offers options to automatically resize high resolution images, convert to and serve WebP versions of JPG and PNG files, bulk compression and options to disable creation of thumbnails registered by your theme.
Extract from WordPress.org
Are you frustrated by a slow website? Do over-sized images make you say “ewww”… Let EWWW Image Optimizer help you make your site faster, improve your bounce rate, and boost your SEO. But most importantly, make your visitors happier so they keep coming back for more.https://wordpress.org/plugins/ewww-image-optimizer/