Half-Life: Source

Half-Life: Source is a port of Valve's original acclaimed game Half-Life to their new Source engine used for Half-Life 2. It was initially only available in the Silver and Gold Edition Steam packages when buying Half-Life 2, and in the Collector's Edition retail disc package. Later, it could be bought separately through Valve's Steam game delivery system, where it comes with Half-Life: Deathmatch - Source.

It takes advantage of vertex and pixel shaders to create realistic water effects, and can now portray realistic physics effects. It also has new menus, improved lighting and soft shadows, ragdoll character animations, and a 3D skybox replacing the old 16-bit color pre-rendered bitmap skies. The storyline, weapons and levels remain the same as in the original version.

Unlike other Source engine games, Half-Life: Source was scarcely updated after release. Several updates to the Source engine repositories, which this game also uses, introduced bugs that were not present in the release version nor the original Half-Life, especially with the 2013 SteamPipe update. On 17 November 2023, Valve removed Half-Life: Source from Steam searches due to its lack of support and their decision to make the anniversary update of Half-Life the definitive version of the game, but it is still available for purchase regardless, explained by the use of its assets in fan-made Source engine modifications.