On most sites, either JPEGs or PNGs make an excellent choice for the bulk of your images. It is best to stick with one over the other for consistency’s sake. As for GIFs, you’ll want to reserve those for situations when you need to display animations.
Why JPEGs are the best choice
More specifically, JPEGs can enable you to squeeze a bit more performance out of your web pages, due to their high compression ratio, but only if you’re using them for color-heavy images – like all photographs, basically. If you want your site to load as fast as possible, and you don’t mind sacrificing a bit of image quality, JPEG is the best image format for your needs.
However, if you care more about ensuring that all your images look as good as they can, we’d recommend that you go with PNGs instead. This image format retains its high quality even when compressed, and works for both complex and simple images.
You have a lot of options when it comes to what types of images you can use on your website. Ideally, you’ll pick whichever formats enable you to display high-quality images without slowing down your site significantly. If you’re a WordPress user, you’ll be glad to know that WordPress supports all the most popular image formats out of the box.