List of Source engine branches

This is the list of Source engine branches, including third-party branch.

Official

Release date	Title	Developer	Platforms	Source code & SDK	Notes
7 Oct 2004	Source 2004	Valve Corporation	PC: Windows	GitHub (unofficial archive) (includes SDK code & tools)	First released with Counter-Strike: Source, later used by Half-Life 2, Half-Life: Source. Later received HDR update in 2005 with the release of Half-Life 2: Lost Coast.
1 Jun 2006	Source 2006	Valve Corporation	PC: Windows	Source SDK Base 2006 Source SDK application (includes SDK code & tools) GitHub (unofficial archive) (SDK code only)	Released alongside Half-Life 2: Episode One, all previous Valve games using Source 2004 were upgraded to this branch. See Features section for the list of changes and new features.
10 Oct 2007	Source 2007	Valve Corporation	PC: Windows Consoles: Xbox 360, PlayStation 3	Source SDK Base 2007 Source SDK application (includes SDK code & tools) GitHub (unofficial archive) (SDK code only)	Also known as "The Orange Box engine branch". Released alongside The Orange Box (Half-Life 2: Episode Two, Team Fortress 2 and Portal). Half-Life 2 and Half-Life 2: Episode One were also ported to this engine branch exclusively on consoles (Xbox 360, PlayStation 3). See Features section for the list of changes and new features.
17 Nov 2008	Left 4 Dead engine branch	Valve Corporation	PC: Windows, macOS (2010) Consoles: Xbox 360	Left 4 Dead Authoring Tools Left 4 Dead 2 Authoring Tools (no SDK Base, content-based mod only) Source code: Not publicly available.	Released in 2008 with the release of Left 4 Dead, and later updated for Left 4 Dead 2 in 2009. Runs on newer version of Source, which does not requires Half-Life 2 base content to run. Game files from this branch were stored into VPK files, as opposed to GCF. See Features section for the list of changes and new features.
3 Jun 2009 [confirm]	Source 2009 Source Multiplayer	Valve Corporation	PC: Windows, macOS (2010)	Source SDK application (no SDK Base, content-based mod only) Source code: Not publicly available.	Released in 2009 with an update to Day of Defeat: Source, and later Team Fortress 2. All Source 2006 games (except Half-Life: Source and Half-Life Deathmatch: Source) were upgraded to this branch with the release of the Mac update in May 26, 2010 (Half-Life 2 and its episodes), and later on Windows in June 10, 2010, alongside Counter-Strike: Source update which features many new changes from Hidden Path Entertainment.
19 Jul 2010	Alien Swarm engine branch	Valve Corporation	PC: Windows	Alien Swarm - SDK (includes SDK code & tools) GitHub (unofficial archive) (SDK code only)	Released in 2010 with the release of Alien Swarm, a remake of the Unreal Tournament 2004 mod with the same name. This is the only post-Orange Box engine branch with it's source code publicly available for free.
18 Apr 2011	Portal 2 engine branch	Valve Corporation	PC: Windows, macOS, Linux (2014) Consoles: Xbox 360, PlayStation 3, Nintendo Switch (2022)	Not publicly available.	Released in 2011 with the release of Portal 2.
21 Aug 2012	CS:GO engine branch	Valve Corporation	PC: Windows, macOS, Linux (2014) Consoles: Xbox 360, PlayStation 3	Not publicly available, but leaked.	Released in 2012 with the release of Counter-Strike: Global Offensive, featuring many changes not available with previous branches. This engine branch was later made obsolete with the release of Counter-Strike 2, which is the port of CS:GO to the Source 2 engine, which also adds new gameplay features and remakes several maps. The full source code for this branch alongside Team Fortress 2 (Source 2013) was leaked in 2018.
7 May 2013	Source 2013 Singleplayer Source 2013 Multiplayer	Valve Corporation	PC: Windows, macOS, Linux Mobile: Android (Nvidia Shield) Consoles: Nintendo Switch	Tools available on bin folder. (may not be included in some games) GitHub (SDK Code - Singleplayer) GitHub (SDK Code - Multiplayer, legacy)	Released in 2013, during the transition to the new content distribution system called SteamPipe (which has its downsides of breaking many Source mods running on previous branches). All remaining Source 2006 games (Half-Life: Source and Half-Life Deathmatch: Source) and all Source 2009 (including Source Multiplayer sub-branch) were upgraded to this branch. Source SDK Launcher was deprecated on this branch in favor of launching tools (Hammer, Model Viewer, etc.) through .bat files, located in game name\bin. Aside from that, new features has been added along with other improvements. Half-Life: Source and Half-Life Deathmatch: Source, which was upgraded from Source 2006 to Source 2013, now suffering from multiple game-breaking bugs and graphical glitches on some chapters, requiring users to install a unoffical patch in order for it to function correctly. Full source code for this branch (alongside CS:GO) was leaked in 2018. Source SDK 2013 Multiplayer has been succeeded by Team Fortress 2 branch in Feburary 18, 2025.
9 Jul 2013	Dota 2 engine branch	Valve Corporation	PC: Windows, macOS, Linux	Not publicly available.	Released in 2013 with the release of Dota 2, and the last official Source engine branch. This engine branch was later made obsolete with the release of the Dota 2 Reborn update, completely upgraded to the new Source 2 engine.
19 Apr 2024	Team Fortress 2 branch	Valve Corporation	PC: Windows, Linux	GitHub (Game code only)	Also referred as Source SDK 2013 Multiplayer v2. It is a updated version of Source 2013 Multiplayer, developed from updates to Team Fortress 2, which have incompatible  ABIs, i.e. mods/tools compiled for will not work under without updating interfaces. It adds features such as VScript, WebM (replaces Bink on x64), 64-bit support, and more...; Aside from Team Fortress 2, Half-Life 2: Deathmatch runs on this branch after the 20th Anniversary update, then in February 18, 2025, all remaining Source 2013 Multiplayer games, as well as SDK Base 2013 - MP, have been upgraded to this branch.
Release date	Title	Developer	Platforms	Source code & SDK	Notes

Third-party

Release date	Title	Developer	Platforms	Source code	Notes
11 Mar 2014	Titanfall branch	Respawn Entertainment	PC: Windows Consoles: Xbox 360, Xbox One, Xbox Series X/S, PlayStation 4, PlayStation 5, Nintendo Switch	Not publicly available.	Released in 2014 with the release of Titanfall, and later modified further starting with Titanfall 2 and Apex Legends. Runs on heavily modified version of the Source engine, forked from the Portal 2 engine branch.
6 Mar 2020 5 May 2015 (early access)	Xengine	Crowbar Collective	PC: Windows, Linux		Known for being used in Black Mesa. Forked from Source 2013 Multiplayer, with additions from Team Fortress 2. The engine is also hybrid of Portal 2 engine branch and Left 4 Dead engine branch. It featured completely new lighting systems (CSM, Deferred lighting), and many other features listed here.
7 Jan 2024	Strata Source	Strata Source (formerly Chaos)	PC: Windows, Linux		Strata is a modified version of the CS:GO engine branch that combines the features of both Counter-Strike: Global Offensive and the Portal 2 engine branch, along with many improvements that bring Source close to modern standards.
Release date	Title	Developer	Platforms	Source code	Notes