FlashFirebug – A Firefox Extension For Debugging AS3 Flash Files
For many web designers and developers, Firebug is probably one of most vital tools while building and debugging web apps.
Besides Firebug, it requires Flash Player content debugger 10 or higher and enables us to inspect display list, change properties and see the warnings, errors + traces for any Flash file.
It can also work with multiple Flash files on a web page and display the elements inside the file as a directory tree.
The extension is designed to perform fast and, optionally, it can be disabled to be used only when it is needed.