Forza Horizon 4 servers support up to 72 players.
Unlike the earlier Horizon games’ more limited online structure, Forza Horizon 4 uses a synchronised shared world. A server instance can contain as many as 72 players, allowing drivers to explore the map, encounter one another and join activities within the same evolving environment.
The number refers to the shared server population, not necessarily the number of competitors in every race. Individual events can use smaller groups, while the wider world continues to host other players. That distinction helps explain why a 72-player server does not mean every race has 72 cars on the starting grid.
The game’s shared world is set in a fictionalised Great Britain and includes changing seasons. In the separate Eliminator mode, introduced in December 2019, the headline format also involved up to 72 players in a battle-royale-style event.