When downloading an image using a Preset Size or Custom Resize, you can choose whether to download in either JPG, PNG or WEBP.
Not sure what the difference is or which one to use? Here's a quick guide:
JPG
(also known as JPEG - they are the same file format)
Ideal for photos that you want to use on the web (e.g. website, intranet or social media)
Sacrifices some image quality for a smaller file size
Converts any transparency in an image to white (so a transparent background on a logo, for example, would get converted to solid white)
PNG
Ideal for graphics and logos
No loss in image quality, which means the file size will be larger (especially for detailed images like photographs)
Supports transparency (so if you have a logo on a transparent background, the background stays transparent)
WEBP
Highly optimised for web usage
Smaller file sizes than both PNG and JPG with comparable image quality
Supports animations, with smaller file size than GIFs