The game, initially released as a mod in January 1999, and created by Daniel "Sven Viking" Fearon, enables players to play together on online servers to complete levels, many of which are based on the Half-Life universe but include other genres.

The modification enables a server to be hosted, so many players can cooperate (along with any allied non-player characters) to complete levels against creatures and other enemies that are controlled by the computer.

The game can also be played in single-player mode, taking advantage of improvements over the original Half-Life that were made by the modifications, particularly the artificial intelligence used by non-player characters.

[2] Fearon was sent a copy of Half-Life by Valve prior to its official release, and while playing it, he toyed with the game's code, figuring out how to spawn enemy creatures in multiplayer maps.

Though they had developed a large number of assets for the mod, they were hindered by the lack of the SDK, which had been pushed back along with the release of Half-Life 2.

[3] The two got official approval from Valve to release Sven Co-op on Steam as a standalone title in 2012, though opted to wait nearly a year to announce this in July 2013 to give their team time to develop a hotfix for the current version of the mod.