Today at work we had a curious situation — a simple 40k banner was somehow using 23k of Actionscript bytes even though its only code was a number of stop()’s and some navigateToURL()’s and URLRequests. How was this possible?

Theory #1 was that tweens could have had something to do with it. Could the new tweening system actually be using AS? I created a test file including classic tweens, shape tweens, and “new” tweens. The result was 0 Actionscript bytes.

Theory #2 was that Blending Modes could be a factor. Again, 0 bytes.

Theory #3 was that 3D transformations could be the culprit. There was a simple 3D effect used at one point in the banner. To test this, I made an extremely basic AS3 file and applied a slight 3D rotation to its only MovieClip. I published and, voila, there were 23k of Actionscript bytes in the size report.

It’s odd that classic and “new” tweens hardly affect file size at all but 3D manipulations have to include a significant sized AS library. Unfortunately I don’t know what resulted in this decision by Adobe, but if anyone has some insight I’ll be sure to make an addendum to this post.