The original Forza Motorsport series developed by American developer Turn 10 Studios focuses on primarily simulation racing around a variety of both real and fictional tracks, and seeks to emulate the performance and handling characteristics of many real-life production, modified, and racing cars.

From the start, Turn 10's approach to the series has been to broaden its appeal to the general audience and not limit it to racing enthusiasts, passionately highlighting car culture along the way.

[14] Every Forza title includes an artificial neural network used by its AI racers, called Drivatars, a portmanteau of driver and avatar.

In early Forza titles, the Drivatars ran on a Bayesian neural network, which calculates possible solutions to a problem and their probabilities based on player data collected from previous races before selecting the one with the highest confidence value.

Since Forza Motorsport 5, the Drivatars have used a reinforcement learning paradigm, and have recorded racing data of all players connected to the cloud as part of the Xbox Network.

Turn 10 inserted a layer of control between player and AI inputs that allows for the developers to modify Drivatar behavior so as to prevent unexpected results.

[13] Playground Games was co-founded in 2009[16] in Leamington Spa, England, by Gavin Raeburn, Trevor Williams, and Ralph Fulton, all former employees of Codemasters.

Raeburn was known for his role in developing critical hits such as the Dirt and TOCA series, but he became inspired by the open world environment of Test Drive Unlimited, and so left Codemasters feeling that it lacked the resources to fulfill his ambitions.

Other members of Playground have included former employees of Bizarre Creations, Black Rock Studio, and Sony Liverpool—all racing game companies of the United Kingdom.

At the same time, Turn 10 Studios began seeking out businsesses in hopes of finding one willing to expand and branch out its franchise.

[24]: 98–153  Common elements established by this game for future Forza titles include effects of damage on car performance,[24]: 190–192  a paint job and decal editor,[24]: 95–97  the ability to tune one's car and purchase upgrades using in-game credits won at previous races,[24]: 70–84  and assist functions that make driving easier but at the cost of bonus end-of-race credits.

Prior to the game's release, Microsoft launched Forza Motorsport Showdown, a four-part TV miniseries on Speed.

It is also the first game in the franchise to feature a cockpit camera, as well as the ability to capture, edit, and share clips of gameplay.

[25][30][31] For Forza Motorsport 4, which was released on October 11, 2011, Turn 10 Studios partnered with BBC's Top Gear to get Jeremy Clarkson to provide commentary for the new Autovista mode, which allows players to explore a certain selection of cars in great detail.

The game expanded on the Top Gear partnership by having Richard Hammond and James May provide commentary alongside Clarkson.

[34] The Autovista mode was renamed Forzavista, and new to the series are open-wheel cars and integrated cloud computing, which collects and uses driving data from connected players to shape Drivatar behavior and through which user-generated paint jobs can be downloaded.

[25][35] Forza Motorsport 6, released for Xbox One on September 15, 2015, introduces new gameplay elements such as racing in the rain or at night, an online ranking system called Leagues that matches players based on their skill level, and game-modifying cards.

The game incorporates many different gameplay aspects from previous Forza Motorsport titles, like the large variety of cars, realistic physics, and high-definition graphics.

Horizon features the physics of Forza Motorsport 4, which have been optimized to work on the more than 65 variants of terrain said to be present in the game.

The game is set in Southern France and Northern Italy, and the playing field is three times the map of its predecessor.

Additionally, its single-player and multiplayer modes have merged to allow for seamless connectivity, where other players can join in or drop out of the host's session without interrupting the latter's progress.

This expansion features a new area called "Thrilltopia" and adds orange and blue Hot Wheels track with loops, jumps, corkscrews, boost pads, half-pipes and more.

It introduces a dynamic four-season scheme that rotates on a weekly basis and changes aspects of the environment, such as rivers drying in the summer.

Also new is Forza Link, an AI assistant that tracks one's progress and preferred means of playing the game and the players they meet online.

Gameplay involved players controlling only the acceleration and braking by pressing and releasing a button or a touch screen; steering was handled automatically.

Although its visuals were praised, it was criticized for its overly simplistic controls, its implementation of the freemium model, and tedious gameplay.

[96] Forza Motorsport 5 was bought by over one third of all Xbox One owners in February 2014, which Eurogamer estimates amounts to 1.3 million copies.

[98] The first Forza Motorsport received critical acclaim for its realistic handling mechanics, paint job editor—both features that have reappeared in every subsequent version of Forza—and Xbox Live integration.

Every main title in the Forza Motorsport and Forza Horizon series has received an aggregate review score of at least 80 out of 100 on Metacritic;[73][74][75][76][77][79][80][81][82][83][84][85][86][87][88][90] the only exception is Forza Motorsport 5,[78] which at launch received criticism for featuring fewer cars and tracks compared to its predecessors (though some of the content withdrawn from the final release reappeared in the form of DLCs), as well as microtransactions in which players could purchase in-game tokens to progress faster, to the latter of which Turn 10 Studios responded by increasing rewards won at the end of a race and decreasing car prices.

[101] The concept of Forza Horizon received positive remarks for demonstrating the potential that the new series had, although the game's Drivatars' AI and sparse multiplayer were criticized.