What the mod does
ATG Core carries the parts more than one ATG mod needs, so they are written and fixed once rather than copied. Today the substantial one is the settings system: a way for a server owner to change any ATG mod’s settings by editing a plain text file on the server, with no mod of their own and no Workbench.
It is not a gameplay mod. Loading it on its own changes nothing you can see.
Why a mod would depend on it
Every ATG mod works standalone. Its settings live in its own config file, which you can override the ordinary Arma way — by making a mod of your own and overriding the file in it. That works, and it needs the Workbench tools installed, a mod built, and a rebuild each time you change your mind.
With ATG Core loaded, the same settings become readable from a JSON file in the server’s profile directory. Nothing is rebuilt, nothing is uploaded, and one server’s tuning is a file you can copy to another. See Configuration.
The dependency is soft in both directions. A mod that supports the system runs normally without Core; Core does nothing on its own. Nothing breaks either way.
Load order matters
ATG Core must load before any mod that uses it. This is the one setup detail that bites, because getting it wrong does not produce an error message.
A mod compiles its Core support in only if Core is already present when that mod is compiled. Load Core second and every mod that depended on it silently drops to its own config file — and because the server and its clients can disagree about that, the symptom is usually players being rejected for a content mismatch rather than anything pointing at load order.
If ATG mods are ignoring their JSON file, check load order before anything else.
Mods that use it
- ATG Scenario — objectives, placement and faction score.
- ATG Garmin Vitals — wrist-worn vitals monitor. Its complete settings file is on the Configuration page until the mod has pages of its own.