w3blog

Open Flash CS4, create new AS3 FLA, add as3swf.swc and paste this on frame 1:
import com.codeazur.as3swf.SWF;
var swf:SWF = new SWF(root.loaderInfo.bytes);
trace(swf);
Trace output:
[SWF]
Header:
Version: 10
FileLength: 149405
FileLengthCompressed: 149405
FrameSize: (550,400)
FrameRate: 24
FrameCount: 1
Tags:
[...]

While testing my AS3 SWF library as3swf yesterday, i found that MXMLC (the compiler that comes with the Flex SDKs)  writes undocumented SWF tags to the SWFs it produces.
I was able to identify two so far:
ProductInfo (Tag ID 41)
The ProductInfo tag contains infos about the tool used to generate the SWF, as well as the [...]