Building everything from scratch
Before the licensed engine era, making a game required building the systems that ran the game as well as the game itself. A studio making a 2D platformer in 1988 needed to write sprite rendering code, collision detection, level loading, input handling, audio playback, and save file management before any game-specific code could be written. These systems were not trivially difficult — sprite rendering that ran at 60 frames per second on 1988 hardware required careful optimisation — and they were largely the same from one platform game to another. Every studio was rebuilding equivalent systems rather than building on shared foundations, because there were no shared foundations commercially available.
The custom engine was not merely a technical necessity but a competitive advantage: a studio with a rendering engine that produced superior visuals than competitors had a product that players could see was different from alternatives. Sega's R360 (1990) hardware, id Software's Doom engine (1993), Silicon Graphics's Reality Engine — each was a competitive differentiation as much as a production tool. The engine was part of the product's identity, and the decision to build or license was a decision about whether the engine's technical distinction was part of the commercial proposition.
Quake and the first licensing era
id Software licensed the Quake engine to other studios beginning in 1996, establishing the commercial model that engine licensing would follow for the subsequent decade: a flat fee or royalty arrangement that gave the licensee access to the engine's source code, the ability to modify it for their own product, and technical support from id's engineering team. The Quake engine licensees included Ritual Entertainment (Sin), Raven Software (Hexen II), and Valve (Half-Life) — games that used the Quake engine's rendering and physics systems as their foundation and built game-specific systems on top.
Half-Life's engine — GoldSrc, Valve's substantially modified version of the Quake engine — was in turn licensed to other studios and used as the basis for Counter-Strike's engine infrastructure. The chain of derived engines — Quake begetting GoldSrc begetting the Counter-Strike engine — illustrated how licensing enabled studios to build on existing work without requiring the engine author's direct involvement after the initial license agreement. The engine became infrastructure that studios could inherit and modify without rebuilding from the bottom, which reduced the time to production for studios that didn't need to differentiate on engine technology.
Epic Games' Unreal Engine, first licensed with the original Unreal (1998), pursued a more aggressive licensing strategy than id Software. Where id licensed the Quake engine with relatively limited commercial ambition, Epic positioned Unreal Engine as a commercial product unto itself, investing in the engine's quality and documentation as a business priority independent of the games Epic made with it. By Unreal Engine 3 (2006), Epic's licensing business was generating significant revenue from games across multiple platforms and genres — shooters, role-playing games, racing games — that had no connection to Epic's own game development output. The engine had become a standalone business within Epic's structure, and the commercial games Epic made with the engine (Unreal Tournament, Gears of War) served partly as showcases for the technology's capabilities to prospective licensees.
Unity and the democratisation
Unity Technologies launched Unity 1.0 in 2005 targeting the Mac game development market — a small, underserved market where the available engines were Windows-only and expensive. The initial version was modest in capability compared to Unreal Engine 3 but significantly more accessible: the editor interface was designed around visual drag-and-drop composition of scenes rather than text-based configuration, the scripting language (JavaScript and later C#) was more accessible than Unreal's C++ requirement, and the pricing was radically different — free for basic use, with paid tiers for commercial developers above a revenue threshold.
Unity's free tier was the most significant commercial decision in the engine's history. By making a functional game engine available without upfront cost, Unity eliminated the financial barrier that had prevented individual developers and very small studios from using commercial engine technology. An independent developer who couldn't afford Unreal's licensing fees could build a complete game in Unity without paying until the game generated revenue, and the revenue threshold was high enough that a game needed to reach commercial success before Unity's fees became significant. The model was simultaneously a subsidy for independent development and a commercial strategy: Unity acquired the loyalty of a generation of developers who had learned to make games in Unity and who would, if their projects succeeded, become paying customers.
By 2015, Unity was the engine used in more mobile games than any other, and by 2020 it was used in approximately 50 percent of all mobile games and a significant proportion of PC and console games. The democratisation that Unity represented — the ability of small teams or individual developers to make complete, commercially viable games without building engine technology — changed the composition of the games industry. The independent developer movement of the 2010s, which produced games including Monument Valley, Hearthstone, Pokémon GO, and Hollow Knight, was built primarily on Unity's accessibility. The engine that had been designed to serve Mac developers became the infrastructure on which a significant portion of the commercial game market ran.
What engine licensing changed
The licensed engine's most significant consequence was the separation of engine development from game development as disciplines. A studio that licensed Unreal Engine didn't employ engine programmers; it employed game programmers who worked within the engine's existing systems. The skills required changed: expertise in low-level rendering code, memory management, and platform-specific optimisation — the skills that defined the best engineers in the pre-engine era — became less relevant than expertise in the specific APIs and design patterns of the engine being used. Unreal developers were Unreal developers; Unity developers were Unity developers; the skills were partially transferable between engines and partially specific to each engine's architecture.
The engine's consolidation — a market where two or three engines were used in the majority of games — also created systemic vulnerabilities that the pre-engine era hadn't had. A bug in Unreal Engine that affected all games built on it simultaneously was a bug affecting hundreds of studios and thousands of players at once. Unity's 2023 pricing change — an announcement that Unity would charge a fee per installation above certain revenue and download thresholds — produced immediate and severe backlash from developers who had built businesses on assumptions about Unity's pricing model that the company was now changing retroactively. The scale of the backlash was proportionate to the scale of the dependency: a generation of developers had built studios and businesses on Unity's pricing model, and a change to that model was a change to the economic foundation of their businesses. Engine licensing had made game development more accessible and had simultaneously made a significant portion of the industry dependent on the commercial decisions of two or three engine companies whose interests were not always aligned with the developers using their products.