Update Jan 24 -09: The Flash Tracer that works with Firefox 3 has to be downloaded from the creator’s own site. The one at Mozilla Addons doesn’t work with 3.x (yet). In the instructions below I have therefore used the link to his own site.

If you’re developing for Flash/Flex the FlashTracer can be quite a nifty plugin. It lets you see the flash player trace output directly in a sidebar in you browser. Outputting debugging info is something I use all the time while developing and I have tried several times to get FlashTracer to work, but haven’t managed, so I usually have a textarea inside my flash/flex project with a custom debug output. I guess I have been too impatient before but today I sat down and read through some posts about it. This is how I eventually got it to work on my Mac:

1. Make sure you’re using the latest Flash Player Debug version. Download it here

2. Install the plugin (of course)

3. Open the FlashTracer sidebar in FireFox. Click the Preferences button.

4. Under the area named “Select output file” click browse and point the plugin to the flashlog.txt file your debug player outputs. In my case (being on a mac) it was here:
/Users/{username}/Library/Preferences/Macromedia/Flash Player/Logs/flashlog.txt

The plugin will ask if you want to replace the file, which is stupid because you will want to read from the file, not write to it, but that’s just how it is. Don’t let it scare’ya.

5. Save/close preferences.

6. Restart FireFox.

That should do it.