You can profile only Web applications on Windows 8 in Modern UI mode; Desktop and Mobile applications are not supported.
Before you profile an application on Windows 8 in Modern UI mode, locally or remotely, you need to follow these steps:
Modify the registry setting
Modify the trusted site setting
After you profile an application remotely on Windows 8 in Modern UI mode, a mm.cfg file is created at C:\Users\UserName. If you try to profile an application locally after that, ensure that you delete the mm.cfg file before you start profiling. Otherwise, an ActionScript error occurs.
Before you start profiling the application
If the computer on which Flash Builder is running is not on Windows 8, and you want to profile your application on a Windows 8 computer, ensure that the project that you are profiling in Flash Builder should be a server-type project.
Alternatively, if your project is a non-server project, do the following:
Profile the application
While using Internet Explorer (IE) Modern UI browser for profiling, if you run into any issues, see this Tech Note for more information.