Alien Swarm
Co-operative multiplayer game and complete code base available for free.
Estimated lifetime revenue
Free-to-play
Revenue comes from in-game items and microtransactions, which our price-based model doesn't estimate. The player count below is how many people own it, not what they spent.
Est. players
822.1K
people who own it
Reviews
21.6K
Review score
95%
9.5/10
Concurrent players
19
read Sep 17, 2026, 15:00 UTC
About
About the game
Alien Swarm is a game and Source SDK release from a group of talented designers at Valve who were hired from the Mod community.
Available free of charge, the game thrusts players into an epic bug hunt featuring a unique blend of co-op play and squad-level tactics. With your friends, form a squad of four distinct IAF Marine classes. Plan your attack using an unlockable arsenal of weapons with countless loadout configurations against a wide variety of aliens. Blaze your way through an overrun, off-world colony, eradicating the alien infestation in environments ranging from the icy planet's surface, to a subterranean lava-flooded mining facility.
Along with the game get the complete code base for Alien Swarm that features updates to the Source engine as well as the SDK. Alien Swarm adds 3rd person camera, depth of field, improved dynamic shadows and a wide variety of gameplay additions to the Source engine.
Available free of charge, the game thrusts players into an epic bug hunt featuring a unique blend of co-op play and squad-level tactics. With your friends, form a squad of four distinct IAF Marine classes. Plan your attack using an unlockable arsenal of weapons with countless loadout configurations against a wide variety of aliens. Blaze your way through an overrun, off-world colony, eradicating the alien infestation in environments ranging from the icy planet's surface, to a subterranean lava-flooded mining facility.
Along with the game get the complete code base for Alien Swarm that features updates to the Source engine as well as the SDK. Alien Swarm adds 3rd person camera, depth of field, improved dynamic shadows and a wide variety of gameplay additions to the Source engine.
- Tactical, 4 player co-op action game with a top-down perspective
- Complete game code and mod tools
- Unlock persistent items by gaining levels
- Over 40 weapons and equipment with countless loadout configurations
- 4 unique classes and 8 unique characters
- Matchmaking, Steam Cloud, Steam Stats
- 64 achievements
- Tile-based map generation tool
- Powered by Source and Steam
Genres
