Fantastic, little known gem

Even after using Smush.it and EWWW image optimizer on my media library, Prizm created massive savings.

I would agree that you should make sure you have a backup of files before running them through the Prizm API, but if you use these precautions then it is fantastic.

Would only add that the controls are all over the place so the UI/frontend could do with revamp. FYI, currently you need to go to Settings>Media to enter your API key.