In 2018, six years after Strelok fought his way to the heart of Chernobyl, the Zone remains a dangerous place...

S.T.A.L.K.E.R.: Anomaly is a free and standalone fangame based on the S.T.A.L.K.E.R. series, developed by fans using a customized fork of the X-Ray Engine that powered the original S.T.A.L.K.E.R. games. It uses the assets from and combines the maps of the first three games in the series to create the largest version of the Zone seen yet.

Like the official games, S.T.A.L.K.E.R.: Anomaly is a first-person shooter with RPG elements and an emphasis on survival. The player must eat and drink to stave off hunger and thirst, sleep regularly to avoid weariness, and maintain their weapons and armor to ensure that they keep functioning reliably when they are needed most. The repair system has been deeply expanded, with dozens of new items added to the game to aid in maintaining, repairing, and upgrading equipment.

There are nine different factions to choose from when creating a character: Loners, Bandits, Clear Sky, Duty, Freedom, Mercenaries, the Military, Ecologists, and the Monolith. Three additional factions, Renegades, Sin, and UNISG, can each be unlocked by completing each of the first three chapters of the campaign. Each faction has their own headquarters in the Zone that the player can start from as well as their own dynamic questlines to follow. However, the factions that are hostile to all but their own (such as Monolith) cannot trigger the main story campaign of Anomaly.