Amx extension stands for either Adobe Motion Exchange or Half life mod files. These extensions can be opened by After Effects software.

1-Adobe Motion Exchange:
With this software, you may create videos and animations. If you need to display these works with different Adobe softwares such as After Effects you should save the file with amx extension.  

Also, there is another software called Livemotion which also use amx file. However, Adobe firm stopped the production of Livemotion in 2003. 

2-Half Life mod file:

Some mod files ( development and patch) are also saved with amx extensions. These mode files are developed for some games which are created by Valve firm. You may get detailed information about game from its web page:

What to use amx

After Effects

which page related to amx file

amx Related Searches

You can check related links about amx fileextension.