[6] The game takes place in a synchronised shared world, compared to the AI-driven 'drivatars' from its predecessors, with each server supporting up to 72 players.

Players have the opportunity to buy in-game houses which unlock new items, cars and game-play perks, including Horizon Promo and the ability to fast travel anywhere on the map.

[8] Returning from Forza Horizon 3, Wheelspins are prize spins with random rewards ranging from cars, Credits (in-game currency), emotes, horns, and clothing.

[10] Also returning from the past two games, British drum & bass label Hospital Records provided a soundtrack composed of 20 original tracks from various label artists, as well as an unreleased track by Fred V & Grafix titled "Sunrise", made for the game's opening cinematic.

Every four weeks, at the end of every Spring season, a new update for the game was released introducing new gameplay content, cars, and cosmetic items.

The first of these updates, at the end of October 2018, saw the addition of the Route Creator tool and a new Horizon Story, British Racing Green.

50% and 80% completion of both the Series and the current season rewards drivers with an exclusive car or cosmetic item, consisting of the Common, Rare, Epic, or Legendary rarity.

With the Series 9 update in May 2019, the developers implemented a system to prevent wallriding—the practice of driving into a curved wall on the outside of a corner instead of braking and steering, thus allowing the player to carry more speed through a corner—and high-speed collisions in online multiplayer.

The system predicts the occurrence of a collision between two cars with a large difference in speed and ghosts the faster vehicle, preventing rammings (both intentional and accidental).

[25] In July 2019, as part of the Series 11 update, a special Horizon Story was added in collaboration with BBC's Top Gear.

The missions, narrated by presenter Chris Harris, provided players with rewards including the "Track-tor" (a race-modified tractor featured in Series 25 of the show) and the Mercedes-Benz G63 AMG 6x6.

In this mode, players start by driving around the game world in a fairly slow, weak car such as a 1965 Mini Cooper.

As players roam the safe zone, they can acquire car drops that contain more powerful vehicles that randomly appear on the map.

[31][32] In the following days, a fictional car, known as the 2058 Quadra V-Tech, was included in the game as part of the release of Cyberpunk 2077.

[49] While criticising the festival system as confusing, The Guardian enjoyed the different feel of the game's cars, "Playground Games’ attention to car-modelling detail means that a garage full of 50 vehicles offers 50 slightly different experiences, and lets you develop a curated collection of favourites".

[50] Polygon criticised how the game world felt like a theme-park version of England, "everything has the faint whiff of an idealised 1950s about it, a place of ordered pub gardens and rosebushes.

[51] GamesRadar+ felt the setting of Britain wasn't as interesting as 3's Australia, but liked the online modes, saying "messing around with a group of mates was always fun in Burnout Paradise, and Forza Horizon 4 gives you everything you need to do that, if it’s your bag".

[52] GameSpot praised the new additions Forza Horizon 4 added, "You're also now able to create your own custom courses, and the series' more creative pursuits return with story missions--which feature things like stunt driving and nice homages to other racing games".

[54] On 18 January 2019, Playground Games announced that they had reached 7 million registered users after the launch of Fortune Island expansion.