Dota 2 Reborn moved Dota 2 to which Valve game engine?

Dota 2 Reborn moved Dota 2 to Valve’s Source 2 game engine.

Valve announced Dota 2 Reborn in June 2015 as a major overhaul that would replace the game’s original Source-engine client. The update was not merely a visual refresh: it introduced a redesigned interface, a new approach to community-created custom games, and the technical foundation Valve wanted for future Dota 2 development.

Reborn first appeared as an opt-in beta in June 2015. It officially replaced the original Dota 2 client in September, making Dota 2 the first released game to use Source 2. The transition also enabled support for newer technologies, including the Vulkan graphics API, which later became an optional rendering path.

The move caused technical problems for some players and was followed by a temporary decline in the game’s player base. Over time, however, Source 2 became the foundation for other Valve projects, including Artifact, Dota Underlords, Half-Life: Alyx, and Counter-Strike 2. Source, the engine used by the earlier Dota 2 client, is therefore the common mix-up: Reborn replaced Source with its successor, Source 2.