| Release date |
Title |
Developer |
Platforms |
Source code |
Notes    
|
| 7 Oct 2004 |
 Source 2004 |
Valve Corporation |
PC: Windows |
 GitHub (unofficial archive)
(gamecode only) |
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 application
GitHub (unofficial archive)
(gamecode only) |
Released with the release of 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 application
GitHub (unofficial archive)
(gamecode only) |
Also known as "The Orange Box engine branch". Released with the release of The Orange Box (Half-Life 2: Episode Two, Team Fortress 2 and Portal). Half-Life 2 and Half-Life 2: Episode One was 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 |
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) |
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 Mac update in May 26, 2010 (Half-Life 2 and it's 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
GitHub (unofficial archive)
(gamecode 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 remake several maps.
The full source code for this branch alongside Team Fortress 2 (Source 2013) was leaked in 2020. |
| 7 May 2013 |
 Source 2013 Singleplayer
 Source 2013 Multiplayer |
Valve Corporation |
PC: Windows, macOS, Linux
Mobile: Android (Nvidia Shield)
Consoles: Nintendo Switch |
GitHub (Singleplayer, HL2 20th anniversary)
GitHub (Multiplayer, legacy) |
Released in 2013, during the transition to the new content distribution system called SteamPipe (which has it's 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 has been 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 2020.
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 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), 64-bit support, and more...; Aside from Template:Tf, Half-Life 2: Deathmatch runs on this branch after 20th anniversary update, then in February 18, 2025, all remaining Source 2013 Multiplayer games, aswell as SDK Base 2013 - MP, have been upgraded to this branch. |
| Release date |
Title |
Developer |
Platforms |
Source code |
Notes
|
Available doc translations 
