The best open source alternative to Counter-Strike is Xonotic. If that doesn't suit you, our users have ranked more than 50 alternatives to Counter-Strike and 13 is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to Counter-Strike are AssaultCube, Cube 2: Sauerbraten, AssaultCube Reloaded and ET: Legacy.
Xonotic is a free (GPL), fast-paced first-person multiplayer shooter that works on Windows, OS X and Linux. The project is geared towards providing addictive arena shooter gameplay which is all spawned and driven by the community itself.
AssaultCube is a free, multiplayer, first-person shooter game, based on the CUBE engine.
Taking place in realistic environments, with fast, arcade gameplay, it's addictive and fun!
Cube 2: Sauerbraten is a free multiplayer/singleplayer first person shooter, built as a major redesign of the Cube FPS.
A free-and-open-source first-person-shooter aimed at improving the classic game, AssaultCube!
Wolfenstein: Enemy Territory is a free multiplayer first-person shooter. Set during World War II and heavily focused on team work, it was initially released in 2003 by Splash Damage and id Software. More than a decade after its release, after spending countless hours of...
Nexuiz was originally developed by Lee Vermeulen and Forest ‘LordHavoc’ Hale, who started Alientrap in the summer of 2002. The goal of the project was to create a high quality first person shooter that could be played freely across all platforms in one package: PC, Mac, and...
A truly free and open source multiplayer shooter, no strings attached. Have casual deathmatch matches on various scenarios. Build your own levels with the ingame editor and assets that come with the game, or just play around and use it as a sandbox.
Tremulous is a free, open source game that blends a team based FPS with elements of an RTS. Players can choose from 2 unique races, aliens and humans. Players on both teams are able to build working structures in-game like an RTS.
Digital Paint: Paintball 2 is a Paintball game that started out as a mod for quake 2 but then took on a life of its own as an open source fps game with a global player and clan management system.
Jake2 is a Java 3D game engine. It is a port of the GPL’d Quake2 game engine from id Software. To use the Jake2 engine you need either the data files from the original game or from the demo version that is available for download from ftp://ftp.idsoftware.com.
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Xonotic is a fast-paced FPS arena videogame, while counterstrike is a tactical FPS