Every mod is a zip, but the layout inside decides whether it can be installed automatically. Four shapes cover almost everything:
1. Add-on DLC (dlc.rpf)
A dlc.rpf (usually inside a folder of the same name). Maps, vehicles and some characters. The client writes it into dlcpacks and registers the dlclist entry.
2. OIV package (assembly.xml)
An assembly.xml at the package root — the OpenIV installer format, common for graphics mods. The client can execute its file copies and archive edits.
3. Add-on character (AddonPeds)
Model files xxx.ydd / xxx.yft / xxx.ytd / xxx.ymt. The client writes them into the character library and registers the list; spawn them from the toolbox.
4. Script pack (.dll / .asi / .ini)
SHVDN scripts (dll) go into scripts; ASI plugins must sit in the game root. Both need the environment pack.
Why some mods say unsupported
Messy layouts (models mixed with preview images, replacement files dropped into attachment folders) or unusual formats are detected as unknown and refused — that is a safety net, not a bug. Send us the package and we will adapt it.
See also: Required components · Install guide