It's impressive, indeed! I guess they use some feedback loop when recompressing, because there doesn't appear to be no quality loss, even on the smallest detail

It's impressive, indeed! I guess they use some feedback loop when recompressing, because there doesn't appear to be no quality loss, even on the smallest details. I've tried one file of 1.4MB of an Australian nature landscape. Recompressed went under 400KB. I wonder if there isn't an offline tool available. For free if possible :)