Fabric API is the add-on needed to run most mods for Fabric loader. This library does not add anything to the game, it is needed only to launch other mods. Therefore, there is no need to install it separately. It is needed for all launchers except MCLauncher.
How to Install Fabric API:
- Make sure you have it installed Fabric.
- Download the file for your version of the game.
- Put it in the ‘mods’ folder, which is located in the game folder.