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To let players join your American Truck Simulator server without every mod, set mods_optioning: true in server_config.sii (in Files > .local > share > American Truck Simulator) and restart. This only works for mods whose author marked them optional for multiplayer (mp_mod_optional: true in the mod’s manifest.sii). Map mods are never optional. Players must also allow optional-mod servers in the session browser filter.

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How optional mods work

If any of the three is missing, the mod counts as required and players need it to join.

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Which mods can be optional?

SCS allows a mod to be optional only if it doesn’t change gameplay in a way that needs every player to have it, and only the mod’s author can mark it. Map mods ignore the setting and are always required.

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How to turn on optional mods

1

Export your packages with the mods active

The optional mods still go in your server packages. Activate them in your game and run export_server_packages. See export server packages.
2

Stop the server

Stop the server and upload the new server_packages.sii and server_packages.dat.
3

Edit server_config.sii

Open server_config.sii in the same folder and change:
4

Save and start

Save the file and start the server. The setting stays after restarts.

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How to check if a mod is optional

Open the mod’s .scs or .zip file with an archive tool and look in manifest.sii for mp_mod_optional: true. If the line is missing or false, the mod is required. Don’t edit another author’s mod to change this; ask the author instead.

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Frequently asked questions

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Why do players still need a mod I made optional?

Check all three points in the table: the mod’s manifest, mods_optioning: true on the server and the player’s session browser filter. Also restart the server after editing the file.

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Can I make Coast to Coast or another map mod optional?

No. Map mods ignore the optional setting, so every player needs them. See Coast to Coast map.

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Is mods_optioning on by default?

No. A new server has mods_optioning: false.

ATS server guide

Every ATS page in one place.

Install mods

Mods in your game and on the server.

Export server packages

Send your mod list to the server.

server_config.sii explained

Every setting and its limit.
Checked against the official SCS mod manager documentation and dedicated server documentation on 30 October 2026; panel steps tested on our Game Panel (American Truck Simulator dedicated server 1.61s). Details may change with game updates.

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Need Extra Help?

If you encounter any issues, our support team is ready to assist:

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Last Updated: October 2026