Garry’s Mod – Running several instances of Gmod (or other source games)

Intro

 
For some reason this doesn’t seem to be common knowledge as it took me three years to figure out how to do this. This guide describes the process and some methods for running multiple Source games at once 
 
 

Process and Methods

• Navigate to your games install folder, shift+right click to quickly open PowerShell, or just cd there in cmd 
   
   
   
• Make sure a source game is already running beforehand (otherwise this command doesn’t do anything different!) 
• In cmd type your games executable (most of the time, ‘hl2’) and type -multirun after a space, in PowerShell, type .\ before the executable 
   
   
   
• In most cases, you will also need to specify “-game [sourcemod name- cstrike/tf2, etc.]” as most games include their own folder and hl2, or multiple games share one folder (HL2, Episodes, and HL1 Source), and an error will occur. if you don’t see the hl2 folder or there’s only one sourcemod folder, this is not needed (like in Gmod’s case, it does not include any other sourcemod folder) 
   
   
   
• This will bypa*s the “Only one instance of the game can be running” dialogue 
• The command should work on Mac and Linux systems, but the process will be a bit different 
• Keep in mind connecting to an online multiplayer game with the same game will disconnect you 
• Running a new game while one is already in a game/not the title screen, it can take some time to initialize and will freeze the currently running game for some time. If your first instance of the game is only on the title screen the second will be significantly faster to start 
• If you are one to put shortcuts to games on your desktop, you can also create shortcuts to these executables and add the -multirun argument to the shortcut’s properties, however it may not launch Steam if it is not running like Steam’s URL shortcuts do 
   
   
   

Other Methods/Incompatible Games/Other Info

• In the case of Counter-Strike: GO, it seems to produce and error with this method. Instead, you can use -textmode in launch options and run the game through Steam. This may also work with other newer Source games in the event -multirun produces and error. (Using -textmode with most other games only displays the games console in the window, but for some reason this is a feature removed in CS:GO but it still bypa*ses “only one instance”) 
   
   
• In the case of Portal 2, neither method seems to work, but there may be a specific workaround for it as well

Conclusion

 
I write this because since learning about -multirun, I’ve always tried running from Steam launch options in games, but when a game is already running, it is impossible to press Play on it again because of how Steam works, but running the executable from their install folders works how I expected it should. I can’t guarantee this will work with ALL Source games, but it seems highly likely for the majority of pre-2013 games that still bear the executable ‘hl2’ 
 
 
 

I hope you enjoy what we shared today about Garry’s Mod – Running several instances of Gmod (or other source games). If there is anything, you want us to add, please let us know via comment below! See you soon! And thanks!