Launch parameters

Last updated: July 16, 2026

Launch parameters are variables passed to a game server at the time of start-up. These variables load before any other configuration variables and are separate from configuration variables and the server.json file. Launch parameters are best suited for loading information that the server needs access to immediately after starting.

You might want to use a launch parameter instead of a configuration variable in the following scenarios:

Initialise a port number.
Set the log directory.

However, it makes more sense to use configuration variables instead of launch parameters in most cases.

You must encase each launch parameter variable in dollar symbols ($$), two on each side. For example, a launch parameter named port converts to . The following code snippet has example launch parameters.

-port port -queryport queryport -log logdir

Server variables

Like build configuration variables, you can use the following server-specific variables in your launch parameters. The following table has example server variables, each with a type, description, and example value.

Variable	Type	Description	Example Value
`commandline`	string	A string of the launch parameters passed to the game server or application on launch	`-config path/to/server.json`
`configdir`	string	The directory that contains the Unity configuration server.json.	`/mnt/unity/`
`fleetid`	string	The ID of the fleet of which the server is a member.	`5050693b-0bea-4752-858b-52c074d485fa`

Default launch parameters

The following sections display the default launch parameters for games made with Unity and games made with Unreal.

Note: Build configuration variables are encased in double dollar symbols ($$).

Unity

The default launch parameters for games made with Unity include -nographics, -batchmode, and -logFile.

Tip: The recommended best practice is to use sessions to integrate Multiplay Hosting into your Unity game. Refer to Unity Editor command line arguments to learn more about the different flags you can use.

-nographics -batchmode -port port -logFile logdir/Engine.log

Launch Parameter	Description
`-nographics`	Run the game executable without graphics.
`-batchmode`	Run Unity in batch mode. In batch mode, Unity runs command line arguments without the need for human interaction.
`-port`	Specify the port clients can use to connect to the game server.
`-logFile`	Specify the location where the server saves log files. It accepts a directory relative to the server ID and can include build configuration variables.

Depending on the game, the launch parameters might also include the query port (queryPort) and query protocol (queryType).

-nographics -batchmode -port port -logFile logdir/Engine.log -queryPort queryport -queryType querytype

Launch Parameter	Description
`-queryPort`	Specify the network port on which the server should bind for query protocol traffic.
`-queryType`	Specify the query protocol supported by the build the server is running.

Unreal

The default launch parameters for games made with Unreal include -log, and -port.

Tip: Refer to Unreal Engine command line arguments to learn more about the different flags you can use.

-log=$serverid.log -port=port

Launch Parameter	Description
`-log`	Specify the location where the server saves log files.
`-port`	Specify the port clients can use to connect to the game server.

Depending on the game and SDK you're using, the launch parameters might include the query port (queryPort) and query protocol (queryType).

-log=$serverid.log -port=port -queryPort queryport -queryType querytype

Launch Parameter	Description
`-queryPort`	Specify the network port on which the server should bind for query protocol traffic.
`-queryType`	Specify the query protocol supported by the build the server is running.