A mod (short for "modification") is an alteration that changes some aspects or one aspect of a video game, such as how it looks or behaves. Mods may range from small changes and tweaks to complete overhauls, and can extend the replay value and interest of the game.
The Internet provides an inexpensive medium to promote and distribute user created content like mods, an aspect commonly known as Web 2.0. Video game modding was described as remixing of games and can be therefore seen as part of the remix culture as described by Lawrence Lessig. Modding a game can also be understood as the act of seeking and installing mods to the player's game. Mods have arguably become an increasingly important factor in the commercial success of some games, as they add a depth to the original work. Developers such as id Software, Valve Corporation, Mojang AB, Bethesda Softworks, Firaxis, Crytek, Creative Assembly and Epic Games provide extensive tools and documentation to assist mod makers, leveraging the potential success brought in by a popular mod like Counter-Strike.
In cases where mods are very popular, players might have to clarify that they are referring to the unmodified game when talking about playing a game. The term vanilla is often used to make this distinction. "Vanilla Battlefield 1942", for example, refers to the original, unmodified game.
As early as the 1980s, video game mods have also been used for the sole purpose of creating art, as opposed to an actual game. This can include recording in-game actions as a film, as well as attempting to reproduce real-life areas inside a game with no regard for game play value. This has led to the rise of artistic video game modification, as well as machinima and the demoscene.
A total conversion is a mod of an existing game that replaces virtually all of the artistic assets in the original game, and sometimes core aspects of gameplay. Total conversions can result in a completely different genre from the original.
Examples of famous total conversions include Counter-Strike (1999), whose developers were hired by Valve Software to turn it into a commercial product, Defense of the Ancients (2003), which was the first MOBA to have sponsored tournaments, and Garry's Mod (2004), for which fans created thousands of game modes over its decade-long development.
Many popular total conversions are later turned into standalone games, replacing any remaining original assets to allow for commercial sale without copyright infringement. Some of these mods are even approved for sale despite using the IP of the original game, such as Black Mesa.
An overhaul mod significantly changes an entire game's graphics and gameplay, usually with the intent to improve on the original, but not going as far as a complete remake. This can also include adding revised dialog and music.
Examples of overhaul mods include Deus Ex: Revision, which was given permission from publisher Square Enix to release on Steam alongside the original game, and GTA 5 Redux, which not only improves the original game's textures, but also adds a new weather system, visual effects, and adjusts the wanted system, weapons, and vehicle handling.
An add-on or addon is a typically small mod which adds to the original content of a specific game. In most cases, an add-on will add one particular element to a game, such as a new weapon in a shooting game, A new Unit or Map in a strategy game, a new vehicle or track in a racing game, items in a game like Minecraft, or additional contents in simulation games (such as new pilotable airplanes (e.g., the Airbus A330 or Boeing 787 Dreamliner) and scenery packs for Microsoft Flight Simulator X). This can be accomplished without changing any of the original game's existing content. Many games are flexible and allow this, however that is not always the case. Some add-ons occasionally have to replace in-game content, due to the nature of a peculiar game engine. It may be the case, for example, that in a game which does not give a player the option to choose their character, modders wishing to add another player model will simply have to overwrite the old one. A famous example of this type of mod can be found for the Grand Theft Auto series wherein modders may use downloadable tools to replace content (such as models) in the game's directory. The Left 4 Dead series can also be modded with individual add-ons which are stored in a .VPK format, so that a player may choose to activate a given mod or not.
An unofficial patch can be a mod of an existing game that fixes bugs not fixed by an official patch or that unlocks content present in the released game's files but is inaccessible in official gameplay. Such patches are usually created by members of the game's fan base when the original developer is unwilling or unable to supply the functionality officially. Jazz Jackrabbit 2 has an unofficial patch which adds and fixes many of its features. One downside of this type of mod is that leaked content can be revealed. An example is the Hot Coffee mod for Grand Theft Auto: San Andreas, which unlocks a sexually explicit minigame. The ESRB changed the rating of GTA:SA from Mature (M) to Adults Only (AO). In the fourth quarter of 2005, Rockstar released a "clean" version of the game with the "Hot Coffee" scenes removed (Grand Theft Auto: San Andreas 1.01), allowing the rating of the game to be reverted to its original Mature rating. In May 2006, a similar event occurred with Elder Scrolls IV: Oblivion.
An art mod is a mod that is created for artistic effect. Art mods are most frequently associated with video game art, however modified games that retain their playability and are subject to more extensive mods (i.e. closer to total conversions) may also be classified as art games. Art mods are usually designed to subvert the original game experience. One example is the Velvet-Strike mod for Counter Strike in which the players spray-paint anti-violence messages in multiplayer games as a form of performance art. Another example is Robert Nideffer's Tomb Raider I and II patches which were designed to subvert the unofficial Nude Raider patch of the late 1990s by altering Lara Croft's sexual orientation. The origins of the art mod can be traced to the classic 1983 mod Castle Smurfenstein (a humorous subversion of Castle Wolfenstein which replaces the Nazi guards with Smurfs). The very first art mod, however, is generally considered to be Iimura Takahiko's 1993 AIUEOUNN Six Features (a modification of Sony's "System G").
After EA lost the license and ended the support for the MVP Baseball 2005, the game's modding community continues the support and releases updated roster lists every year as also alternative leagues (e.g. MVP Caribe, a total conversion).
Due to the increasing popularity and quality of modding, some developers, such as Firaxis, have included fan-made mods in official releases of expansion packs. A similar case is that of Valve Corporation, when they hired Defense of the Ancients lead designer IceFrog in developing Dota 2.
For example, in the Civilization IV expansion Beyond the Sword: two existing mods, Rhye's and Fall of Civilization and Fall from Heaven made their way into the expansion (the latter through a spin-off called Age of Ice).
Most mods do not progress very far and are abandoned without ever having a public release. Some are very limited and just include some gameplay changes or even a different loading screen, while others are total conversions and can modify content and gameplay extensively. A few mods become very popular and convert themselves into distinct games, with the rights getting bought and turning into an official modification.
A group of mod developers may join together to form a "mod team".
Doom (1993) was the first game to have a large modding community. Mods for Quake (1996) such as "Capture the Flag" and "Team Fortress" became standard features in later games in the shooter genre.
The most well-known mod is the Half-Life multiplayer mod Counter-Strike, which was released shortly after the original game. Approximately one million games are hosted on dedicated servers per day. Counter-Strike is probably the best example of a modification that turns into a retail game. Another renowned mod is Team Fortress, which was based on the Quake engine and eventually became a whole series of games: Team Fortress Classic, Team Fortress 2, and an unofficial mod made originally as a fan-made sequel to TFC, Fortress Forever.
Mod-making tools are a variety of construction sets for creating mods for a game. Early commercial mod-making tools were the Boulder Dash Construction Kit (1986) and The Bard's Tale Construction Set (1991), which allowed users to create game designs in those series. Much more successful among early mod-making tools was the 1992 Forgotten Realms: Unlimited Adventures from Strategic Simulations, Inc., which allowed users to construct games based on the game world that was launched with the Pool of Radiance game.
By the mid 1990s, modding tools were commonly offered with PC games.
Later mod-making tools include The Elder Scrolls Construction Set which shipped with Morrowind, the World Editor for Warcraft III: Reign of Chaos, the Aurora toolset which was included with Neverwinter Nights, FRED and FRED2, the mission editors for Freespace and FreeSpace 2 respectively, the Obsidian tool set for Neverwinter Nights 2, the Garden of Eden Creation Kit SDK for Fallout 3, and the Valve Hammer Editor which is used to create maps for Half-Life 2 and other games that use the Source engine.
There are also free content delivery tools available that make playing mods easier. They help manage downloads, updates, and mod installation in order to allow people who are less technically literate to play. Steam for Half-Life 2 mods is an example.
The potential for end-user change in game varies greatly, though it can have little correlation on the number and quality of mods made for a game.
In general the most modification-friendly games will define gameplay variables in text or other non proprietary format files (for instance in the Civilization series one could alter the movement rate along roads and many other factors), and have graphics of a standard format such as bitmaps. Publishers can also determine mod-friendliness in the way important source files are available (some programs collect their source material into large proprietary archives, but others make the files available in folders).
Games have varying support from their publishers for modifications, but often require expensive professional software to make. One such example is Homeworld 2, which requires the program Maya to build new in-game objects. However, there are free versions of Maya and other advanced modeling software available. There are also free and even open-source modeling programs (such as Blender) that can be used as well.
For advanced mods such as Desert Combat that are total conversions, complicated modeling and texturing software is required to make original content. Advanced mods can rival the complexity and work of making the original game content (short of the engine itself), rendering the differences in ease of modding small in comparison to the total amount of work required. Having an engine that is for example easy to import models to, is of little help when doing research, modeling, and making a photorealistic texture for a game item. As a result, other game characteristics such as its popularity and capabilities have a dominating effect on the number of mods created for the game by users.
A game that allows modding is said to be "moddable". The Elder Scrolls V: Skyrim as well as its predecessors, The Elder Scrolls III: Morrowind and The Elder Scrolls IV: Oblivion, are examples of highly moddable games, with an official editor available for download from the developer. Daggerfall was much less moddable, but some people released their own modifications nevertheless. Some modifications such as Gunslingers Academy have deliberately made the game more moddable by adding in scripting support or externalizing underlying code. Supreme Commander set out to be the 'most customisable game ever' and as such included a mod manager which allowed for modular modding, having several mods on at once.
The games industry is currently facing the question of how much it should embrace the players' contribution in creating new material for the game or mod-communities as part of their structure within the game. Some software companies openly accept and even encourage such communities. Others though have chosen to enclose their games in heavily policed copyright or Intellectual Property regimes(IPR) and close down sites that they see as infringing their ownership of a game.
For cross-platform games, mods written for the Windows version have not always been compatible with the Mac OS X and/or Linux ports of the game. In large part, this is due to the publisher's concern with prioritizing the porting of the primary game itself, when allocating resources for fixing the porting of mod-specific functions may not be cost-effective for the smaller market share of alternate platforms. For example, Battlefield 1942, ported by Aspyr for Mac OS X, had file access issues specific to mods until the 1.61D patch. Unreal Tournament 2004 does not have a working community mods menu for the Mac OS X version and, until the 3369 patch, had graphics incompatibilities with several mods such as Red Orchestra and Metaball.
Also, mods compiled into platform-specific libraries, such as those of Doom 3, are often only built for the Windows platform, leading to a lack of cross-platform compatibility even when the underlying game is highly portable. In the same line of reasoning, mod development tools are often available only on the Windows platform. id Software's Doom 3 Radiant tool and Epic Games' UnrealEd are examples of this.
Mod teams that lack either the resources or know-how to develop their mods for alternate platforms sometimes outsource their code and art assets to individuals or groups who are able to port the mod.
The mod specialist site for Macs, Macologist, has created GUI launchers and installers for many UT2004 mods, as well as solving cross-platform conversion issues for mods for other games.
In January 2005, it was reported that in The Sims 2 modifications that changed item and game behavior were unexpectedly being transferred to other players through the official website's exchange feature, leading to changed game behavior without advance warning.
After the Hot Coffee mod incident, there were calls from the industry to better control modders.
In early 2012, the DayZ modification for ARMA 2 was released and caused a massive increase in sales for the three-year-old game, putting it in the top spot for online game sales for a number of months and selling over 300,000 units for the game.
In 2015, members from the Grand Theft Auto fan site GTAForums reported instances of malware being circulated through modifications written using the .NET Framework for Grand Theft Auto V. Two of the modifications in question, namely "Angry Planes" and "No Clip", came with code for loading a remote access tool, and a keylogger for stealing Facebook and Steam account credentials. The modifications in question have since been taken out of circulation, with affected players being advised to change their social media account passwords and disinfect their computers.
Mod packs are groups of mods put into one package for download, often with an auto-installer. A mod pack's purpose is to make an easy download for downloading multiple mods, often with the goal of resolving cross-mod interactions that can happen, or to make the original game easier or more difficult.
Copyright law, as it relates to video games and mod packs, is an evolving and largely unsettled legal issue. The legal uncertainty revolves around which party is legally the 'copyright owner' of the mods within the pack -- the company that produced the game, the end-user that created the compilation, or the creators of the individual mods..
Some regard the fan use of copyrighted material in mods to be part of a "moral economy", and develop norms about the reuse of this material. Additionally, the copyright laws of many countries contain 'fair use' provisions that protect non-commercial use of a copyrighted work, though the extent to which game mods are protected by those provisions is uncertain.
In April 2015, Valve Corporation implemented a "paid mod" feature onto Steam; the first game to implement this feature was The Elder Scrolls V: Skyrim. The move resulted in a swift backlash from the modding community, and after an enormous influx of complaints of overpriced mods, content that had been published without its creator's consent, and concerns over mods that contained third-party copyrighted content (i.e, material that neither Valve nor the mod creator owned), Valve discontinued the 'paid mod' feature entirely and agreed to refund those that spent money to purchase a mod.. The removal of the system itself was also criticized.
Another factor in MVP’s favor: The game allows greater access to its innards than most titles. [...] 2K’s failure to match MVP’s approval rating despite several years of running unopposed on the PC market, made MVP the go-to game for modders even as it lost its looks relative to 2K and The Show. The community’s support peaked from 2005 through the first PC edition of 2K in 2009, tailed off for a time, and then ramped up again once Take-Two abandoned the PC market in 2013 and canceled 2K entirely last year. A decade of EA development made MVP the best baseball game on the PC market in 2005, and a decade of amateur development has helped it keep that title in 2015.