This free online image examination tool gives you a lot of information found in the given image.
There are a lot of articles about online image compression tools in the net, most of them are very superficial. Usually they end with a simple: "It generates smaller pictures, so it's got to be better."
Learn why such statements are most of the time meaningless, understand the technical background, and find out which tool you should use as of today.
Then it would be nice to share it with others.