Alien Swarm

Alien Swarm

Valve · July 19, 2010 · Free to Play, Co-op, Action, Multiplayer, Online Co-Op

Alien Swarm is free to play — no purchase needed. We track it so you know if that ever changes.

PC
Very Positive95% · 21,63577Metacritic22playing now
This game is free to play. Get it on Steam →

Trailers & screenshots

Watch the Alien Swarm trailer →

Alien Swarm price

Alien Swarm is free to play — there is no purchase price, on Steam or anywhere else we track. We keep watching it, so if it ever stops being free the price history on this page will show when that happened and what it changed to.

About Alien Swarm

✦ AI summary

Lead a four-person squad of elite marines through a bug-infested alien colony in this free tactical co-op shooter with a top-down perspective, where you'll customize loadouts from 40+ weapons and fight through procedurally varied environments. The complete Source engine code and mod tools are included, making it as much a developer's playground as it is a fast-paced action 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.
  • 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

Alien Swarm — game info

Platforms
Windows
Steam Deck
Playable
Player modes
Single-player, Co-op
PC Game Pass
Not included

Alien Swarm in the rankings

What Steam players say

Recent verbatim reviews from Steam — separate from playze.io community reviews below.

✦ AI summary

Players praise this free shooter for its fun gameplay, thrilling action, and enjoyable multiplayer with interesting creature designs, appreciating its simplicity and nostalgic appeal. Some note the game has limited content depth and imperfect presentation, though enthusiasts of classic shooters find it well worth playing despite these minor drawbacks.

Recommended Sep 25, 2026
A Tearful Review from an 86-Year-Old Gamer: After Playing Alien Swarm, My Body, Mind, and Every Organ Are Different Intro Hello, young gamers. I am 86 years old. On the day my pension came in, my grandson added some money to my Steam account and said, “Grandpa, play this. It’ll prevent dementia.” Well, the dementia is definitely gone now—because I don’t have a brain left to get dementia. The aliens ate it. 1. Physical Changes 1. Hands I used to shake. Parkinson’s-level shaking. I could pick up a peanut with chopsticks and my hand would blur like a hummingbird. After Alien Swarm, my hands don’t shake anymore. Now I can headshot six aliens in a row while calmly telling my team, “Bugs on the left, throw a fire grenade.” But there’s a problem: now when I pick up a peanut with chopsticks, I instinctively hit R to reload. Yesterday at dinner I “reloaded” a bowl of rice onto the floor. 2. Eyes Eighty-six years of life taught me to accept my limits. Alien Swarm taught me that people who accept their limits get eaten by bugs. Now I can spot a medkit versus an ammo box on a screen full of bugs. My eyesight went from “can’t read the TV guide” to sniper-level. The cost: when I see a coc…
2 found this helpful
Recommended Sep 30, 2026
Alien Swarm is actually quite a fun game, even if it's rather short and lacking in content (it only recieved 1 content update and 1 bugfix update). And for a game with only 1 official campaign made up of 7 levels, it has some rather deep-ish worldbuilding if you look closely. Definitely give it a try. If you want more AS, play Reactive Drop.
Recommended Sep 29, 2026
Fun to play, I personally recommend playing with others but if you want the hat trick achievement for the parasite hat you can add bots with console commands to get the achievement with ai.
Recommended Sep 29, 2026
Fun to play as a party
Recommended Sep 27, 2026
its really good i wish there was more
Recommended Sep 25, 2026
good

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