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<Alien Swarm> asw_spawner is a point entity available in Alien Swarm. It is used to spawn and configure aliens. Each spawner can only spawn one type of alien.


Max Num. Of Live Aliens <int>
Maximum number of live aliens that can be present in the level from this spawner at any given time.
Num. aliens we can create <int>
The number of aliens that can spawn before the spawner is exhausted.
Infinitely spawn aliens <bool>
If True then the spawner will constantly spawn aliens until disabled.
Spawn interval <float>
Time in seconds between each alien spawning.
Spawn interval variation <float>
Percentage variation applied randomly to the spawn interval each time an alien spawns. Value must be between 0 and 100. The default 25 will give a 25% variation to the spawn interval, so a 1 second spawn interval would actually be randomly between 0.75 seconds and 1.25 seconds.
Alien Class <choices>
Which class type of alien to produce from this spawner.
Alien Health scale <float>
Multiplier of the alien's default health by this amount. Useful for increasing or decreasing the difficulty of your map. For example: 0.5=50%, 1=100%, 1.50=150%
Alien Speed Scale <float>
Multiplier of the alien's default speed by this amount. Useful for increasing or decreasing the difficulty of your map. For example: 0.5=50%, 1=100%, 1.5=150%
Spawner State <bool>
Spawner's initial state.


; Allow spawn if marines are near <bool>
If set to True, the key 'Prevent spawn if marines are this close' must be adjusted accordingly. Useful for 'magic', non-burrowed spawns where it would look awkward if a player saw it.
Start Burrowed <bool>
If true then the spawning alien will play either it's default or a specific unburrow animation.
Unburrow Idle Activity <string>
Idle animation the alien will play before unburrowing. Not necessary for standard spawns.
Unburrow Activity <string>
If the spawning alien starts burrowed, it'll play this animation on spawn. By default burrowed aliens will climb out of a floor grate, in order to change this please view Swarm Animations
Prevent spawn if marines are this close <float>
Used in conjunction with the 'Allow spawn if marines are near' key; if said key set to True then this value must be adjusted for it to work efficiently. If marines are in the specified radius, the spawner will temporarily stop until the set radius has been cleared.
Long sight range <bool>
If true, aliens from this spawner will be able to see and sense enemies twice as far away as normal. Useful for aliens spawned at a distance that are intended to track the marines. Handy for larger survival maps.
Alien Orders <choices>
Orders given to each alien spawned.
  • Spread Then Hibernate
  • Move To
  • Move To Ignoring Marines
  • Move To Nearest Marine
Alien Orders Target Name <targetname>
Name of the target object used by the 'Move To' order (above).
Name to give spawned aliens <string>
Useful for controlling spawned aliens later on.
Note.png Note:  When specifying the spawned aliens in another entity or Output the names of the spawned aliens are automatically given a numeric value after their name. ex. specified name is 'Drone' and the added value would make it 'Drone_1', so in order to specify all the spawned later on you must add a wildcard to the end of the target, thus becoming 'Drone*'
Check Spawn Point is Clear <bool>
Used to check whether the spawn point is clear of obstruction. E.g. Not blocked by props, marines, other aliens.
Min Skill Level <int>
The minimum skill level for this spawner to function. Skill levels are: 1=easy 2=normal 3=hard 4=insane 0=nolimit
Max Skill Level <int>
The maximum skill level for this spawner to function. Skill levels are: 1=easy 2=normal 3=hard 4=insane 0=nolimit


Pitch Yaw Roll (Y Z X) (angles) <angle>
This entity's orientation in the world. Pitch is rotation around the Y axis, yaw is the rotation around the Z axis, roll is the rotation around the X axis.


Name (targetname) <string>
The targetname that other entities refer to this entity by.
Entity Scripts (vscripts) <scriptlist> (in all games since <Left 4 Dead 2>)
Space delimited list of VScript files (without file extension) that are executed after all entities have spawned. The scripts are all executed in the same script scope, later ones overwriting any identical variables and functions.
Script think function (thinkfunction) <string> (in all games since <Left 4 Dead 2>)
Name of a function in this entity's script which will be called automatically every 100 milliseconds (ten times a second) for the duration of the script. It can be used to create timers or to simulate autonomous behavior. The return value (if present) will set the time until the next call.
Note.png Note: Try to avoid expensive operations in this function, as it may cause performance problems.


  • Infinite even on Easy mode. Will forcibly spawn an infinite amount of aliens when the 'Infinitely spawn aliens' flag is set to True, while playing on easy difficulty.
  • Don't Spawn Uber aliens here. Prevents spawning the stronger variation of drones.
  • Spawned Aliens never sleep. Never idle into the sleeping state, prevents aliens from stopping, appropriate for hold outs.


Ignores Max Alien count from this spawner and spawns one alien of the predefined type.
Enables spawning.
Disables spawning.
Toggles active status.
Toggle spawning status.


Removes this entity from the world.
Removes this entity and its children from the world.
Note.png Note: Entities already remove orphaned children upon being removed, but this input removes all children on the same frame, being marginally faster than Kill.
AddOutput <string>
Adds a keyvalue/output to this entity. It can be potentially very dangerous, use with care.
KV Format: <key> <value>
I/O Format: <output name> <targetname>:<inputname>:<parameter>:<delay>:<max times to fire, -1 means infinite>
FireUser1 to FireUser4
Fire the OnUser outputs; see User Inputs and Outputs.
Use  !FGD
Same as a player invoking +use; may not do anything depending on the entity. Can also be invoked by firing an output that does not specify an input.
RunScriptFile <script> (in all games since <Left 4 Dead 2>)
Execute a VScript file from disk, without file extension. The script contents are merged with the script scope of the receiving entity.
RunScriptCode <string> (in all games since <Left 4 Dead 2>)
Execute a string of VScript source code in the scope of the entity receiving the input. String quotation may be needed when fired via console.
Bug.png Bug: In <Left 4 Dead 2>, the code is executed in the script scope of the entity that fires the output, not the one receiving the input.
Warning.png Warning: Never try to pass string parameters to a script function with this input. It will corrupt the VMF structure because of the nested quotation marks, which then must be removed manually with a text editor.
CallScriptFunction <string> (in all games since <Left 4 Dead 2>) !FGD
Execute a VScript function in the scope of the receiving entity.
SetLocalOrigin <coordinates> (in all games since <Alien Swarm>) !FGD
Send this entity to a spot in the map. If the entity is parented to something, it will be offset from the parent by this amount.
SetLocalAngles <angles> (in all games since <Alien Swarm>) !FGD
Set this entity's angles.


Fired when the Spawner has Spawned it's max number of aliens. Note: If set to infinite spawning, this output will never be fired.
Fired when the spawner has spawned it's max number of aliens AND they have all died. Note: If set to infinite spawning, this output will never be fired.
Fired Each time the Spawner Spawns an Alien.


OnUser1 to OnUser4
These outputs each fire in response to the firing of the like-numbered FireUser1 to FireUser4 Input; see User Inputs and Outputs.
OnKilled  (only in <Left 4 Dead><Left 4 Dead 2>)
This output fires when the entity is killed and removed from the game.