Plans for a successor to the originalSource engine began following the release ofHalf-Life 2: Episode Two in 2007.[1][2] The first engine tech demo was created in 2010 by remaking a map fromLeft 4 Dead 2.[2] Images of this were leaked onto the internet in early 2014.[3] At the 2014Game Developers Conference, Valve employee Sergiy Migdalskiy showed off a Source 2 physics debugging tool being used inLeft 4 Dead 2.[4] Source 2 was first made available viaSteam Workshop tools forDota 2 in 2014 prior to it being officially announced at the 2015 Game Developers Conference.[5] There, Valve stated their intent for it was to allow for content to be created more efficiently.[1][6][7][8] Valve also stated that it would support theVulkan graphics API and use a new in-housephysics engine called Rubikon, which would replace the need for the third-partyHavok tools.[4][9][10]
Gabe Newell, president and founder of Valve, said that the company were prioritizing the development of their own games before they would release the engine and itssoftware development kit to the public. This was to ensure the highest quality for developers; he added that they were intending to make the engine free to use for game developers as long as the game is published on theirSteam service.[5][11][12]
In June 2015, Valve announced that the entirety ofDota 2 would be ported over to Source 2 in an update calledDota 2 Reborn.[13][14][15][16]Reborn was first released to the public as an opt-in beta update that same month before officially replacing the original client in September 2015, making it the first game to use the engine.[17][18][19][20] Source 2 has also been used for Valve'sArtifact andDota Underlords, with the engine later being supported onAndroid andiOS for the latter.[21][22] The engine also supports the creation of games invirtual reality, being used inSteamVR Home, theRobot Repair tech demo withinThe Lab, andHalf-Life: Alyx.[23][24] Source 2 tools made specifically for creating content forHalf-Life: Alyx were released in May 2020.[25]
