Includes Source SDK Games
Discover the best co-op games on Steam. Access estimated total revenue, median sales per game, saturation levels, and top-performing titles to benchmark your project.
Games with Includes Source SDK
Explore all games featuring includes source sdk
Garry's Mod
Garry's Mod is a physics sandbox. There aren't any predefined aims or goals. We give you the tools and leave you to play.
Left 4 Dead 2
Set in the zombie apocalypse, Left 4 Dead 2 (L4D2) is the highly anticipated sequel to the award-winning Left 4 Dead, the #1 co-op game of 2008. This co-operative action horror FPS takes you and your friends through the cities, swamps and cemeteries of the Deep South, from Savannah to New Orleans across five expansive campaigns.
Half-Life 2
Reawakened from stasis in the occupied metropolis of City 17, Gordon Freeman is joined by Alyx Vance as he leads a desperate human resistance. Experience the landmark first-person shooter packed with immersive world-building, boundary-pushing physics, and exhilarating combat.
Counter-Strike: Source
Counter-Strike: Source blends Counter-Strike's award-winning teamplay action with the advanced technology of Source™ technology.
Portal
Portal™ is a new single player game from Valve. Set in the mysterious Aperture Science Laboratories, Portal has been called one of the most innovative new games on the horizon and will offer gamers hours of unique gameplay.
Black Mesa
Relive Half-Life.
No More Room in Hell
The chances of you surviving this all out war of society and the undead are slim to none. Already, there are millions of the walking dead shambling about, searching for food to eat. There's no known cure. One bite can possibly end it all for you. However, you aren't alone in this nightmare.
Left 4 Dead
From Valve (the creators of Counter-Strike, Half-Life and more) comes Left 4 Dead, a co-op action horror game for the PC and Xbox 360 that casts up to four players in an epic struggle for survival against swarming zombie hordes and terrifying mutant monsters.
Fistful of Frags
Multiplayer based, first person enabled, action packed and skill demanding shooter set in the Wild West times. A unique combination of non stop action and slow but powerful weaponry.
Holdfast: Nations At War
Fight on multiple fronts in Holdfast: Nations At War - A multiplayer first and third-person shooter set during the great Napoleonic Era and WW1. Charge into battle with over 150 players per server!
Alien Swarm: Reactive Drop
Co-operative top-down shooter game available for free. An epic bug hunt featuring a unique blend of co-op play and squad-level tactics.
Day of Defeat: Source
Valve's WWII Multiplayer Classic - Now available for Mac.
Day of Infamy
Experience close-quarters battles in iconic WWII settings. Defend the line, storm the beach, torch the enemy, or use a radio to call in fire support. Day of Infamy is a teamwork-oriented shooter that will keep you on your toes and coming back for more with its diverse game modes and authentic arsenal.
Portal with RTX
Experience the critically acclaimed and award-winning Portal™ reimagined with full ray tracing and DLSS 4 in this free DLC for Portal owners. Start thinking with portals, with RTX on.
Half-Life 2: Deathmatch
Fast multiplayer action set in the Half-Life 2 universe! HL2's physics adds a new dimension to deathmatch play. Play straight deathmatch or try Combine vs. Resistance teamplay. Toss a toilet at your friend today!
Double Action: Boogaloo
Double Action is a free stylish multiplayer game about diving, flipping, and sliding your way into action movie mayhem.
Zombie Panic! Source
Dive into the zombie apocalypse with Zombie Panic! Source: a cooperative, survival-horror first-person-shooter. A fast-paced standalone modification.
Pirates Vikings & Knights II
Step into the ultimate three-way war for honor, glory, and gold! This beloved community-driven game brings together swashbuckling Pirates, battle-hardened Vikings, and chivalrous Knights in hilarious and intense class-based combat. Join the fun, embrace the chaos, and fight your way to victory!
BrainBread 2
Grab a weapon, demolish your enemies, level up, become more powerful, let the gore flow, let the limbs fly. BrainBread 2 introduces a zombie fps mixed with RPG / Arcade elements, the game is very action-packed and generally fast-paced.
0Blade Symphony
Prove you are the world's greatest swordsman! Engage in tactical 1 vs. 1 sword fighting, 2 vs. 2, or sandbox FFA, or capture Control Points in a tactical slash-em-up.