Tried it with a few pages. Not a single one worked. Either it just stopped at some number like "258/290 images" or it gave me "There was an error processing ... Please try another URL." or it resulted in "We're sorry, but something went wrong.".
I posted one of your share links into our Slack, and was really impressed with the image it found (your `meta property="og:image"`) & attached in the rich snippet! Nice work!
Imgix has good libraries that can automatically determine client device pixel ratio and other factors that make it easy to request the right sized image per client. I don't work for imgix or get paid by them, I just like their service.
Even on the highest setting the difference is noticeable enough on a retina screen that I couldn't use this tool. Especially when imageOptim does such a good job.
Cool concept though, get some more compression options and you have a real product here.