Source 2013
The 
Source 2013 engine branch (also called SteamPipe branch) is the final iteration of the Orange Box engine branch. It was introduced by Valve in 2013 to replace the archaic GCF file format with the VPK format introduced in the Left 4 Dead engine branch. Major shifts in content mounting occurred, and all Valve games using the Source 2009 and Source Multiplayer engine branches were upgraded to this branch. 
Half-Life: Source, 
Half-Life Deathmatch: Source, and 
Half-Life 2: Lost Coast was also upgraded to this engine branch from the Source 2006 engine branch. The 
custom folder was added to make modding easier and was added as a mounting path for each individual Source game.
While SteamPipe was praised for simplifying how the Source engine mounts content and including previously-unreleased Team Fortress 2 code, it also broke countless numbers of mods and worsened problems already present in the Source 2009 branch, requires more space due to some Source 2013 games (except 
, 
, etc...) containing duplicated Half-Life 2 base content, plus introducing more bugs to Half-Life: Source. It also does not have most of the features that the engine branches from the Left 4 Dead engine branch onwards had. However, the engine branch has been polished over time, with various bugs from previous Orange Box branch have been fixed (such as Dropship container gun being non-functional in Half-Life 2, NPCs eyes not blinking, etc...) and is now the main branch in use by modern non-licensed engine mods.
Sub-branches
Source 2013 is split into three sub-branches. The first two are titled Source 2013 Singleplayer and Source 2013 Multiplayer, which succeeded both 
Source 2009 and 
Source Multiplayer branches, respectively. The two sub-branches are mostly interchangeable, but they use separate codebases, and the Multiplayer branch has some features which are not available in the Singleplayer branch.
Engine updates since 2022 to the version of 
Source 2013 Multiplayer used by 
Team Fortress 2 have resulted in the creation of a new semi-incompatible sub-branch, being the 
Team Fortress 2 branch, which has its own page. All remaining first-party Source 2013 MP games (
, 
, 
, ) and SDK Base 2013 - MP have been also upgraded to this new branch in February 18, 2025, completely succeeding Source 2013 Multiplayer branch (also referred as Source 2013 Multiplayer Legacy).
Source 2013 Singleplayer on the other hand, despite also have new features (introduced with Half-Life 2 Steam Deck and Anniversary Update), mod and tools built on older SDK 2013 SP code are still compatible, however, mods that are built with older SDK 2013 SP code running on top of game built on newer SDK 2013 SP code will not have all features (Steam Input, Radial fog, Classic Particles, HUD Aspect Ratio, etc.) or function correctly. Currently, Valve has yet to release the updated source code for Source SDK Base 2013 SP.
As of 2025, all games on this branch are actively being maintained with bug fixes by Valve and third-party developers. However, for Valve games, only Source 2013 Singleplayer are being maintained, as Source 2013 Multiplayer games have been succeeded by Team Fortress 2 branch.
Tip:Despite the names, both 
and can be used for singleplayer.The Multiplayer branch provides additional features (static prop lightmaps, BSP compression, more ambient cubes per visleaf, and slightly newer code), which may be desirable over the Singleplayer branch if not using a base mod such as Mapbase and not making a single-player mod that does not modify game code.
The
TF2 branch makes some changes which break singleplayer mode, such as dysfunctional save loading[1] and attempting to load any map with maxplayers (singleplayer) and cl_localnetworkbackdoor both set to 1 ( or 
"hl2" only, does not apply to "sourcetest") will also crash the game[2].Features
Half-Life 2, introduced in 2022.New since the Source 2009 and Source Multiplayer engine branches are:
- VPK files and
customfolder - First introduced on Left 4 Dead engine branch and onwards, it was later available on Source 2013, which replaced the old GCF format. Source 2013 also adds support for reading any files from "custom" folder, which makes installing mods easier without overwriting original game files. In some Source 2013 games, such as
Black Mesa, users may need to create the custommanually. Source 2013 uses VPK version 2. 
Linux, 
Android, other OS and cross-platform support- The engine can now run on Linux, Android (for Nvidia Shield), Nintendo Switch and other operating systems/platforms. However, support for these OS outside of official games may be spotty.
- Static prop lightmaps (in all games since )(also in
) - Static props without bump maps can now use lightmaps (albeit with limitations).
- Per-texel color tint masking for models
$blendtintbybasealphais ported from the
Left 4 Dead engine branch. Source 2013 includes an exclusive additional parameter, $blendtintcoloroverbase.- BSP compression (in all games since )(also in )
- BSP maps and packed files can be losslessly compressed on both server and client.
- Direct3D 9Ex / Windows Aero DirectX Extensions (also in
) - Improve performance depending on GPU hardware and drivers. Additionally, running those games on Windows 10/11 will automatically enable fullscreen optimization, which will allow quicker Alt + Tab ⇆.
Bug:Cannot be disabled even with mat_disable_d3d9ex 0 (or Windows Aero DirectX Extensions set to "Disabled"). Applications such as Special K still reports the game using D3D9Ex (but not through FlipEx).
To actually disable D3D9Ex, you will need to use -nod3d9ex. (tested in:)- Raw mouse input
- Directly taking unchanged data from mouse drivers before it goes through operating system enhancements, meaning that mouse input will be exactly 1 to 1.
Steam Deck update
- Gamepad UI (only in
) - Introduced in 2022, Gamepad UI is a modern controller-oriented UI designed for consoles and handhelds like Steam Deck. With the new Gamepad UI, it was more scalable across any resolution (including 4K and higher), unlike the regular VGUI at the time (which, the higher the resolution, the text and UI will become smaller). VGUI (except on consoles
/
), are harder to navigate, and sometime cannot be navigate with a controller. This UI can be also enabled manually by using -gamepadui command line argument, or running the game when Steam Big Picture mode is active.
Enabling Gamepad UI will also enable Vulkan renderer. If your GPU doesn't support Vulkan or if you don't want to enable Vulkan, uses -dx9 alongside the -gamepadui command. - Vulkan renderer (only in
)(only in )(also in 
) - A low-overhead, cross-platform graphics API, successor to OpenGL.
- First introduced in 2022 with Half-Life 2 and Portal. Portal with RTX also uses Vulkan as part of the RTX Remix runtime. Using DXVK, a library used to translate Direct3D calls to Vulkan. This is disabled by default, but can be enabled in supported games by passing -vulkan into the game's launch options.
HL2 20th anniversary update
Note:These features are also available in Half-Life: Source (or mods running on Half-Life 2 base instead of SDK 2013) after Half-Life 2's 20th Anniversary update.- VGUI High DPI support (also in )
- VGUI are now properly scalable on higher resolutions such as 4K (3840x2160).
Bicubic lightmap filtering (also in )- Introduced in 2024, bicubic filtering is used on lightmaps when r_lightmap_bicubic is enabled, smoothing out aliasing caused by the lower resolution of lightmaps. It can be also enabled by setting the Shader detail to "Very High".
- Radial fog (also in
) - Unlike planar-based fog, radial fog does not strengthen or weaken the apparent amount of fog in a particular spot when you rotate the camera.
- You can either use radial fog or planar-based fog by changing env_fog_controller "Use Radial Fog (fogRadial)" KeyValues.
- Continue music playback after loading levels (also in )
- Introduced in HL2's November 26, 2024 Update, music will continue to play after the next level is loaded, instead of stopping completely like in previous versions. Can be toggled using save_transition_music console command.
Team Fortress 2 branch
Team Fortress 2 branch has its own page.
Removed features
- Patching levels with lump files (only in )
- Patching levels using lump files (to change the map entities without recompiling the map) is no longer possible in MP branch, and possibly Team Fortress 2 branch[confirm].
- Built-in VR headset support (SteamVR, Oculus VR, etc...) (only in )
- The option to enable VR headset support in Video Options, originally introduced with the release of Source 2013, was removed in later updates of Half-Life 2 (since 2022 Steam Deck update). Instead, player can install mods such as Half-Life 2 VR Mod to play in VR.
Known issues / Report bugs
To report bugs or find existing issues on this engine branch, see Source games GitHub and Source SDK 2013 GitHub issues page in order to prevent duplicate or outdated bug reports at the wiki.
Availability
Source code
Source code (game, tools) for Source 2013 Singleplayer, Multiplayer and TF2 branch is available on GitHub:
- Source 2013 Singleplayer: Source SDK 2013 GitHub repo.
- Source 2013 Multiplayer (legacy version): Source SDK 2013 GitHub repo.
- Legacy version of SDK 2013 MP code is provided to create & update tools or mods for third-party games built on older SDK 2013 MP code only.
- TF2 branch (newer Source 2013 MP): Source SDK 2013 GitHub repo.
Full source code (such as Hammer), are not publicly available, but it was leaked back in 2018.
Warning:Source code for Source SDK 2013 MP (TF2 branch) has been updated on GitHub. However, the Source 2013 SP SDK provided on Steam and GitHub currently does not include new changes from Half-Life 2 20th anniversary yet. Source 2013 MP SDK on Steam has been updated, however.
Source 2013 Singleplayer
Valve
- 2004 Half-Life: Source (formerly
, 
) - 2004 Half-Life 2 (formerly , , )
- 2005 Half-Life 2: Lost Coast (formerly )
- 2006 Half-Life 2: Episode One (formerly , )
- 2007 Half-Life 2: Episode Two (formerly ,
) - 2007 Portal (formerly , )
- 2022
Portal with RTX
- 2022
- 2013 Source SDK Base 2013 - Singleplayer (AppID: 243730 - Click to Install)
Third-Party
- 2015
Half-Life 2: Update (earlier version) - 2019 Mapbase
- TBA
Half-Life 2 RTX (Demo released on March 18, 2025.)
- TBA
- 2022
Divinia Chronicles: Relics of Gan-Ti - More...
Source 2013 Multiplayer
All first-party games and Source SDK Base 2013 MP have been upgraded to the Team Fortress 2 branch.
If you want to use legacy version of Source SDK Base 2013 - Multiplayer, to play older mods (or use tools) built prior to Team Fortress 2 branch, follow the instructions:
- 1. Open Steam, go to Source SDK 2013 Multiplayer, right click Properties
- 2. A window will open. Go to "Betas", select previous2021 beta branch.
- 3. Steam will automatically re-download the files. Once it's done, run Source SDK Base 2013 MP as normal, or use it's tools.
Third-party
- 2007
Fortress Forever (in development, will replace ) - 2007
Synergy (formerly , , ) - 2008
Empires (formerly ) - 2009
Obsidian Conflict (in development, will replace ) - 2008
Zombie Panic! Source (formerly /[confirm]) - 2011
No More Room in Hell (formerly /[confirm]) - 2013
Counter-Strike Online 2
- 2014
Fistful of Frags - 2016
BrainBread 2 - 2018
Hunt Down the Freeman (formerly ) - More...
Third-party Source 2013 branches
The following games use neither nor , but rather use custom (heavily modified) branches forked earlier versions from both Source 2013 branches, with newer features added on. As such, they may or may not include all features from newer first-party versions of Source 2013, such as LZMA-compressed BSPs or lightmapped MDLs.
- 2006 Garry's Mod (which also support some features from Alien Swarm, Portal 2 engine branch and onwards, such as partial VTF 7.5 support; formerly , )
- Also, with March 2025 update, uses some code from Team Fortress 2 branch for fixing some exploits.
- Also, with March 2025 update, uses some code from
- 2015 Black Mesa (has its own branch known as Xengine, had features such as CSM, deferred lighting and more; formerly )
System Requirements
These system requirements applies to Source SDK 2013 (and some Source 2013 game) only. Some other games may have their own system requirements.
| Windows |
||
|---|---|---|
| Minimum | ||
| Operating system (OS) | XP or later (pre-Steam Deck update) Vista, 7 or later (post-Steam Deck update) |
|
| Processor (CPU) | 1.7 GHz and/or Dual-core | |
| System memory (RAM) | 1 GB (XP) 2 GB (Vista and later) |
|
| Hard disk drive (HDD/SSD) | 10 GB (space would be increased depending how many Source SDK mods is installed) | |
| Video card (GPU) | NVIDIA GeForce 6xxx series, ATI Radeon X1600, Intel HD Graphics 3000 (with 128MB VRAM)
Direct3D 9.0 compatible video card (with atleast DirectX 8.0 compatibility level or higher) |
|
| Other | To play on XP and Vista, run the game without Steam by directly launching the hl2.exe executable. Some games may requires -game <gamename> command line. | |
 macOS (OS X) |
||
|---|---|---|
| Minimum | ||
| Operating system (OS) | OS X 10.5.8, 10.6.3 (up to 10.14.6) | |
| Processor (CPU) | 2.0 GHz and/or Dual-core | |
| System memory (RAM) | 1 GB | |
| Hard disk drive (HDD/SSD) | 10 GB (space would be increased depending how many Source SDK mods is installed) | |
| Video card (GPU) | NVIDIA GeForce 8xxx series, ATI Radeon X1600, Intel HD Graphics 3000
OpenGL 2.1 compatible |
|
| Sound (audio device) | OpenAL compatible | |
Note:By default, 32-bit executable are no longer supported after macOS Catalina (10.15), meaning that SDK 2013 will not work out of the box. User can manually build Intel 64-bit/Apple Silicon executable by following this guide.| Linux |
||
|---|---|---|
| Minimum | ||
| Operating system (OS) | Ubuntu 12.04, SteamOS 1.0 or later Other Linux distros supported. |
|
| Processor (CPU) | 2.0 GHz and/or Dual-core | |
| System memory (RAM) | 1 GB | |
| Hard disk drive (HDD/SSD) | 10 GB (space would be increased depending how many Source SDK mods is installed) | |
| Video card (GPU) | NVIDIA GeForce 8xxx series, ATI Radeon X1600, Intel HD Graphics 3000
OpenGL 2.1 compatible |
|
Note:The system requirements for Linux are unofficial, based off Windows/Mac info, as well as other Source games that support Linux, such as Portal 2.See also
References
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|---|---|---|---|---|
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