This article relates to the game "Portal 2". Click here for more information.

Testing Portal 2 Co-Op Maps Alone/en

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This is a guide on how you can test co-op maps alone utilizing the splitscreen capabilities of the Source engine. This also works for any existing coop maps. It does not require any modifications to the map file itself.

This does not cover the requirements for making a coop level in the first place.

Warning.pngWarning:Game can't run with -tools as it limits the splitscreen to 1

Loading the Map

ss_map mapname
Load mapname in splitscreen 2-player mode. Analogous to map in singleplayer. Like map, it is not required to add the trailing .bsp.
Note.pngNote:If the map name doesn't begin with "mp_coop_", add " *mp" to the end of the command: ss_map mapname *mp
ss_splitmode mode
Changes the splitscreen mode.
ss_splitmode 0: Use recommended settings based on width
ss_splitmode 1: Top-and-bottom split
ss_splitmode 2: Side-by-side split

If your map is stuck at the loading screen, try to shorten the VMF filename and recompile.

Dual Monitors

If you run dual monitors and want to split to each monitor, follow this guide

Controlling the Second Player

If you could actually play the coop map entirely as one player, it wouldn't be a very cooperative map. These are some ways you can control the second player.


in_forceuser playerindex
Take over the second player. All movement and other keybindings will be as if the second player used them. Requires cheats to be enabled.
sv_cheats 1: Turn on cheats
in_forceuser 0: Control player #1 (Atlas)
in_forceuser 1: Control player #2 (P-Body)

To make this easy to use, set a keybinding for it:

BindToggle "z" in_forceuser
Swaps you between first and second player when you push "z".
Note.pngNote:If you are moving, crouching, shooting portals or otherwise performing an action when you change players, you will stop during the change but immediately resume the action when you change back. For instance, if you're holding "w" to move forward, you will stop moving forward as soon as you hit "z" (assuming you use the BindToggle above), but immediately resume moving forward when you hit "z" again even if "w" is no longer being held down. To stop this, simply tap "w" again, or use a more robust keybinding: Bind "z" "-moveleft; -moveright; -use; -forward; -back; -attack; -attack2; toggle in_forceuser".

Use a Controller

This is actually more complicated than it sounds unless you have two controllers available. Source will map actions of the first detected controller to the first player and there doesn't seem to be any way to override this. The workaround is to either have two actual controllers or use trickery to make your computer think it has two controllers.

You can also connect one controller and enter command in_forceuser 1. Then, Atlas will be controled by controller and P-body will be controled by keyboard.

More information for this can be found on the Steam forums.


This allows you to use the extra sets of linked portals without actually changing characters.

change_portalgun_linkage_id integer
Changes portals fired to belong to the specified character or team.
change_portalgun_linkage_id 0: Single-player
change_portalgun_linkage_id 1: Blue
change_portalgun_linkage_id 2: Orange
change_portalgun_linkage_id [3-9]: Extra / Reserved
Note.pngNote:The color appearance of portals is tied to the person firing them. E.g., when Blue fires Orange's portals (linkage_id: 2), they appear blue until Orange fires them again.

Other Useful Console Commands

cmd2 command
Executes command as if typed by the second player.
cmd2 name Player2: Sets the name of the second player
ss_force_primary_fullscreen enable
Makes the first player fullscreen if enable is 1, hiding the second player's view.
ss_pipsplit 3; ss_pipscale 1; ss_pip_bottom_offset 0; ss_pip_right_offset 0 can be used to show only the second player's view

Alternative Way

Open Portal 2 and go to the "Community Test Chambers" (PTI) tab and enter the test chamber editor. Set the gamemode to "Coop" then launch the map. After launching the map, you can follow the instructions below, without having to use in_forceuser. Instead by default, you can press R that triggers swap_ss_input until restarting Portal 2.

Note.pngNote:For some reason this command doesn't work when PTI isn't started and will stop working when closing PTI.

External Links