How IS Mods Work
Insurgency Sandstorm uses mod.io for its mod ecosystem — not the Steam Workshop. Your server downloads mods directly from mod.io on startup, so you don't need to manually upload mod files. What you do need is the mod's numeric ID.
Both the server and connecting clients need the same mods installed. If a client doesn't have a required mod, they'll be kicked from the server on join attempt with a mod mismatch error.
Step 1 — Find the Mod ID
- Go to mod.io/g/insurgencysandstorm.
- Find the mod you want to install.
- The mod's ID is the number in its URL:
https://mod.io/g/insurgencysandstorm/m/mod-name#XXXXXXXThe#XXXXXXXat the end is the mod ID — it's also shown on the mod's page.
Step 2 — Add Mods to Mods.txt
Open or create the file at:
Insurgency/Config/Server/Mods.txt
Add one mod ID per line:
2134567
2298134
2401872
The server will download any mod listed here when it starts, assuming it has internet access.
Step 3 — Enable Mods in Game.ini
Listing IDs in Mods.txt makes the server download the mods, but you also need to activate them. Open Game.ini and add the IDs under the game mode section:
[/Script/Insurgency.INSGameMode]
ActiveMods=2134567
ActiveMods=2298134
ActiveMods=2401872
Note that each mod ID gets its own ActiveMods= line — don't try to comma-separate them on one line.
Step 4 — Restart the Server
After saving both files, restart your server. On startup you'll see mod.io download activity in the server logs. If a mod fails to download (network issue, mod was removed from mod.io), the server will log the error and either skip the mod or fail to start depending on the mod type.
Client-Side Requirements
Players connecting to your server also need the mods installed. They can do this two ways:
- Automatic prompt — when a player tries to join your server and is missing mods, IS will prompt them to subscribe to the required mods on mod.io.
- Manual install — players can find and subscribe to mods at mod.io before joining.
There's no way to make mods optional for clients if ActiveMods is set on the server — they're required for the connection.
Keeping Mods Updated
Mod updates on mod.io are pulled automatically each time your server restarts. If a mod author pushes a breaking update, your server will automatically use the new version after the next restart. Keep an eye on mod changelogs if your server suddenly behaves differently after a restart.
Troubleshooting
- Mod download fails at startup — check that your server has outbound internet access on port 443.
- Clients getting kicked for mod mismatch — confirm the mod IDs in
Game.inimatch exactly what's inMods.txt, and that clients have the same mods subscribed. - Server crashes after adding a mod — some mods conflict with each other or with specific IS versions. Remove mods one at a time to isolate the culprit.