These days, PNGs are a better choice for web images because they support transparency. But you will want to reduce the size of the image to something reasonable. At one point, I had posted a tip on how to use the built-in "sips" tool to convert these files. But the Quick Action is much easier. However, if you want to also resize the dimensions of the images, then you might want to look into using "sips" on the command line.