I was working on a project to optimize the file size of a published .SWF file today. I wasn’t able to reduce the size of my file by that much, but at the same time I was removing assets from the Library of the source .FLA file. I noticed that after saving, the file size of the .FLA was not decreasing. I started to doubt my sanity, so I decided to see what Google had to say on the subject.
I found this helpful blog post on the subject.
Basically, when using Ctrl+S to save a file, the Flash IDE does a quick save. This quick save, doesn’t do anything to optimize the size of the .FLA file. However, if you use the File > Save and Compact command, Flash will compact the file for you.
However, be warned that saving in this way will remove the undo history for the file. So any changes you’ve made since you opened the file will not be recoverable.