Practically an add-on is a DLL on Windows, or a Mach-O bundle on the Macintosh. When you launch Archicad, it looks for the available add-ons in this order:

• It looks for the Add-Ons folder in its own home directory (that is, where you have installed it)
• The designated add-ons folder can be changed in the Add-On Manager dialog of Archicad (Options menu / Add-On Manager…). This path is stored into the system registry under the ‘HKEY_CURRENT_USER\Software\Graphisoft\Archicad xxx\Add-On Manager’ key on Windows. On Macintosh, you don’t have direct access to this information. Next time when you launch the application, the Add-On Manager will enumerate the add-ons from this location.
  Note that until you change the Designated Add-Ons folder from the Add-On Manager dialog, the ‘Default Location’ key is set to %DEFAULT%, which means the Add-Ons folder right next to the application. The ‘Actual Path’ registry entry shows the actual folder where the add-ons are loaded from.
• You can edit the list of loaded add-ons even individually in the Add-On Manager dialog. The full paths of the added, disabled and skipped add-ons are stored in the registry also.

 
If Archicad finds an Add-Ons folder somewhere, it gathers all the appropriate files from it and from its subfolders. Subfolders on any level are skipped when the name of it begins with the a parentheses ‘(‘ character. Add-ons can also be loaded individually in the Add-On Manager (Options/Add-On Manager) in Archicad, which also facilitates enabling and disabling of loaded add-ons. Please note that certain add-ons cannot be unloaded runtime; you’ll have to restart Archicad to disable those.

 
Every file must pass several tests to be considered as a valid Archicad add-on. If the any of the following requirements are not fulfilled the add-on commands will be not mounted into the Archicad.

Required Resources

 
In order to be able to build an add-on you must fulfill some requirements in the source files too. Also there are requirements how to set up compilation options and linking parameters.

Required Functions
Compilation and Linking Issues

 
Please choose a different name for your add-on from Graphisoft’s own add-ons, because it may cause problems with the GS hotlink process.