Since the beginning, JPEG and PNG are the most commonly used image formats in WordPress but with Version 5.8, WebP images are also supported in the media library. As part of the performance focus for WordPress core, WebP image conversion while uploading images might be coming in the later releases.
But… There is a plugin “Performance Lab” by the team behind “WordPress Performance Group” which allows you to enable WebP conversion while uploading JPEG files to your media library.
Give it a try to test and measure the difference it brings by converting images to WebP image format. You can use the MainWP Lighthouse extension to check the Google Lighthouse stats of all Child Sites at once on a single screen.
After installing and activating the Performace Lab plugin, navigate to:
Settings > Performance
The WebP image conversion in the Performance Lab plugin can only be enabled for JPEG format images at the moment. Ideally, other next-gen image formats will be covered by WordPress core later.
Which image formats you use on your site will depend on the desired image quality when those images are being rendered to display for a site visitor.
Different Image Formats for WordPress
If you are using images with transparencies in them then using the PNG image format will be a solid solution.
Besides WebP, AVIF and JPEG XL are the newest next-gen image formats. These image formats offer better compression which means smaller image sizes without loss of quality, saving you Webhosting storage and bandwidth.
If you are trying to find a smaller image size format for site logos then using SVG would be the best way to go since SVG images are vector-based and will scale for all devices without losing the quality.
The best solution is to convert the image format before uploading images to your WordPress website.