I hope that @ma might see this and chime in. The biggest discrepancy that I am seeing is with an ANE. I use his NativeWebView ANE, and it is pretty large because it contains Chromium. On Windows, the folder holding it inside the META-INF folder is 172MB. On Mac, it seems that either a large part of it is getting chucked out, or it is getting compressed much more efficiently. The thing is, Michael would be the only one who really understands if the footprint of his ANE's might be different on various platforms. If so, it might be an ANE that is causing this big filesize difference, which would mean I am doing nothing wrong.