What system hides enemy units outside allied vision in Dota 2?

The system that hides enemy units outside allied vision in Dota 2 is called fog of war.

Fog of war keeps most of the map concealed unless a location is visible to a hero, allied unit, building, or other source of team vision. This makes information a strategic resource: players must scout routes, watch objectives, protect vulnerable heroes, and infer enemy movements from what is absent from the minimap as well as what is visible.

The mechanic comes from the broader real-time-strategy tradition and is central to Dota 2’s gameplay. Wards, summoned units, heroes, towers, and certain abilities can reveal areas, but vision is temporary or limited by range. Fog of war is often confused with True Sight. True Sight detects invisible units, whereas ordinary vision determines which parts of the map are visible at all. Smoke Screen and Phase Shift are hero abilities, not map-wide visibility systems.