

I just tested the new release. Consider defaulting PNGs to convert to JPEGs unless they have a PNG-specific feature like transparency. Lots of screenshots are initially PNGs, but not because they need any PNG-specific features. Consider: In a test screenshot, it compressed 3.4% with the default 80% setting and PNG->PNG, but for PNG->JPG, it compressed 84.6%.
No, this is all happening in the browser, there are no other image manipulation tools being called.