ISI had been developing simulators since the early 1990s, for both commercial and military clients. The isiMotor2 engine powering rFactor was later licensed for use in rFpro and a range of other simulation products. The decision to omit licensed circuits and teams meant that the initial release shipped with only four fictitious tracks (expanded to seven as of version 1.087), a set of layouts within those facilities, and roughly six vehicle classes including two open-wheel and four sedan categories. Without publisher support from EA Sports — ISI's longtime partner on earlier titles — the game was funded and released independently.
rFactor was positioned as the most accurate race simulator of its time, competing against NASCAR Racing 2003 Season, Live for Speed, and GTR. Its physics engine operated at 15 degrees of freedom and modelled complex aerodynamics alongside an advanced non-linear tyre model. The tyre system simulated the relationship between slip angle, self-aligning torque, and cornering force as a function of temperature and wear — an explicit improvement over the Pacejka model that had dominated earlier simulators. Early reviewer Jon Denton, writing for AutoSimSport, noted that the tyre model did this better than anything that had come before.
A driver-swap feature was introduced in the August 2006 update, enabling multi-driver stints and making it possible to host events of up to 24 hours in length, including Le Mans-style races. The AI opponent system could be trained to learn the ideal line around a specific circuit, with notable improvements to driving speed and consistency arriving in version 1.150. Version 1.250 was released in January 2007, followed by a patch to version 1.255 build F in October of the same year.
Online multiplayer had been a strength of F1 Challenge and rFactor extended it substantially. Matchmaking ran through a central server maintained by ISI, with all available races and practice sessions visible through a web interface called Racecast. Registered drivers had access to career statistics. A headless dedicated server mode allowed a machine to host sessions without rendering graphics, and mixed grids of human and AI drivers were supported. The game's circuit structure — grouping all layouts of a given facility into a single package — reduced the duplication of track geometry that had been a maintenance burden in earlier simulators.
rFactor's plugin interface and comprehensive content-creation toolset enabled the community to produce a vast catalogue of additional cars and circuits. This openness transformed the game into the leading home for historic Formula 1 modification packages: community groups produced recreations of period cars spanning the 1960s through to the early 2000s, making rFactor the de facto standard for sim racing's historic F1 scene during the period between its release and the arrival of more recent platforms. The same engine architecture was licensed for rFpro, the professional driver-training simulator used by motorsport teams.
rFactor was a finalist for PC Gamer US's Best Racing Game 2005, ultimately losing to GTR: FIA GT Racing. Critical response praised the physics fidelity and tyre model while acknowledging that the simulation depth made the game inaccessible to casual players. Reviewer Paul Josua, writing for HonestGamers, concluded that those who did not demand flawless simulation were better served looking elsewhere — but that rFactor did a fine job for its target audience.
ISI developed rFactor 2, which added weather effects, reflections, and accurate shadows across a variety of surface textures. It was released on 28 March 2013 and continued the modding tradition of its predecessor.