Animal Crossing: New Horizons added Dream Islands in version 1.4.0.
Released on July 30, 2020, the update introduced dreaming through Luna, a tapir who appears when the player lies down in a bed. Players could upload a copy of their island and visit other players' uploaded islands without changing the real island or taking items home.
Dream visits are separate from ordinary online multiplayer. Visitors explore a snapshot-like version of an island, while the owner’s actual progress, villagers, buildings, and items remain protected. Each uploaded island receives a Dream Address that other players can use to find it.
The feature required a Nintendo Switch Online membership and an internet connection. Version 1.4.0 also added the first Fireworks Shows and new seasonal Nook Shopping items, which is why it is sometimes remembered as the second Summer Update rather than specifically as the Dreaming update. Later patches fixed problems connected with dreaming, but they did not introduce the feature itself.