Arma 3 players are kicked for signature or mod mismatch

A player connects, the screen loads, then they are dropped with a message about signatures or missing content. Here is the order to check things in.

1. Read the message they get

• Signature check failed means the server does not have the mod's key.
• You cannot play or edit this mission means the client is missing a mod the mission needs.
• Session lost straight after connecting usually means a version mismatch.

2. Install every key

1. Stop the server and open the Files tab.
2. For each @Mod folder, open its keys folder and copy the .bikey file into the keys folder in the server root.
3. One missing key kicks everyone using that mod.
4. Start the server and try again.

Turning off verifySignatures hides the problem and opens the server to modified content. Fix the keys instead.

3. Line up the versions

• A Workshop update on a player's PC makes their copy newer than the server's. Update the server files to match.
• Everyone should load the mods from the same preset, exported from the Arma 3 Launcher.
• Mod load order matters for some mods. The preset keeps the order consistent.

4. Check what the server actually loaded

1. Restart the server and read the first part of the Console.
2. Every mod the server loaded is listed there by name.
3. A mod in your -mod parameter that is not in that list means the folder name does not match the parameter, usually a capital letter or a missing @.

5. Server side mods

Mods that only exist to run on the server belong in -serverMod=. Loading one with -mod= makes the server demand it from clients, which kicks everyone who does not have it.

If the mod list on both sides matches and players are still dropped, open a ticket with the mod preset, the exact kick message and the console output from a fresh start.