Best Tools for Debugging Flash ActionScript 3 (AS3)

SWFWire Debugger can:

• Trace method calls
• Trace object allocation
• Graph frame rate
• Graph memory usage
• Edit properties
• Visually select DisplayObjects similar to FireBug.

It's also open source, and requires no code modifications.

Disclaimer: I wrote this application

DeMonsterDebugger.com has a lot of features (their site describes it best).

• Tracing messages
• Introspection of your application structure
• Testing methods
• Editing properties
• Finding performance issues

And open source! :-)

_{(source: demonsterdebugger.com)}

Flashbuilder has almost everything I need. On top of that, I use JPAuclair's preload profiler , and an in-house developed equivalent to X-Ray.

Adobe Scout, the official debugger by Adobe

Copied from official web site

Works with any SWF

Use Scout to profile and optimize any SWF whether it runs on mobile devices, desktops, or in browsers. And you don't need special debug versions - profile your games in the commercially available Flash Player.

No code changes

Scout works automatically, without any changes in your code. Profile your content in-context with very little effort, find hotspots in no-time.

Project lifecycle use

Scout helps you early in development by detecting problems before you do. Then use the same sophisticated analysis tools on production systems after your game is released.

Mobile profiling? Yes!

A video introduction is available on youtube