Mod (computer gaming)

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2004 Banshee car modification for Grand Theft Auto: Vice City - replacement of original Banshee
Mod or modification is a term generally applied to computer games, especially first-person shooters and real-time strategy games. Mods are made by the general public, and can be entirely new games upon themselves. They can include new items, weapons, characters, enemies, models, modes, textures, levels, and story lines. They also usually take place in unique locations. They can be single-player or multiplayer.

Games running on a PC are often designed with change in mind, and this consequently allows modern computer games to be modified by gamers without much difficulty. These mods can add an extra dimension of replayability and interest. The Internet provides an inexpensive medium to promote and distribute mods, and they have become an increasingly important factor in the commercial success of some games. Developers such as id, Valve, and Epic provide extensive tools and documentation to assist mod makers, leveraging the potential success brought in by a popular mod like Counter-Strike.

Mods can significantly outshine or continue the success of the original game. Playing a mod might even become more common than playing the unmodded original. When talking about playing a game, players might have to clarify that they are referring to "vanilla Battlefield 1942", for example.

Recently, computer games have also been used as a digital-art medium. See artistic computer game modification.



A great many do not progress very far and are abandoned without ever having a public release. One of the most famous vaporware mods was Star Wars Quake, which was never released despite six years of development. 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.

Mods are made for many FPSs, most notably the series based on Quake, Doom, Tribes, Unreal Tournament, and Half-Life. RTS games such as Warcraft III, Total Annihilation and the Command & Conquer series also have many mods.

Among popular mods, none is more well known than the Half-Life multiplayer mod Counter-Strike, which was released shortly after the original game, and upwards of 1 million games per day are hosted on dedicated servers. Counter-Strike is probably the best example of a modification that turns into a retail game.

Mods in general are required to be non-commercial (free) when they include any parts from another mod, or the main game, which by their nature they always do. Some mods also become open source as well.


Mod making tools are a variety of construction sets for creating mods for a game. An early mod making tool was the Bard's Tale Construction Set, released in 1991, which allowed users to create game designs in that 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.

Later mod making tools include the The Elder Scrolls Construction Set which shipped with Morrowind, the Aurora toolset which was included with Neverwinter Nights, and the Valve Hammer Editor which is used to create maps for Half-Life and its sequel, Half-Life 2.

Mod-Friendliness of Games

The potential for end-user change in game varies greatly, though it can have little correlation the number and quality of mods made for a game. For instance the Creatures 2 computer game executable was essential an interpreter for the in-game scripting language, and could potentially have allowed almost any 2d game to be build upon its basis. Other games, such as the sims, will allow modification to certain aspects, such as adding new items and clothes, but not others, such as altering a character's skills or occupation.

In general the most modification friendly games will define gameplay variables in text or other non proprietary format files (for instance in the Civilization (game) 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, while 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 industrial-strength program Maya (software) to built new in-game objects. However, there is a free version available of Maya and other advanced modeling software. There are also free and even open source modeling programs 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 a 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 if mods are created for the game by users.

Unexpected consequences of modding

In January 2005, it was reported that in The Sims 2 modified items created by hard-core players to provide additional benefits were unexpectedly being transfered to other players through the exchange feature, leading to some apparently supernatural effects. [1] (

Example mods for selected games

Battlefield 1942

Since its release in 2002 Battlefield 1942 has spawned a large number of modifications, especially total conversions. Battlefield mods tend to focus on changing the theme and balance (such as more realistic) rather than changing the game mission (conquest game mode). The highlight of most mods are unique vehicles and there use. (See list of Battlefield 1942 mods and List of Battlefield Vietnam mods for a longer listing.)

Command & Conquer: Generals

Some examples of the less common RTS mods for this 3-D RTS.

  • Blitzkrieg II ( - A total conversion mod that recreates the setting of World War II. The player has access to a lot of the more successful units from the war, and can pick the Allies, USSR or Axis powers to play as.
  • HaloGen ( - A Halo: Combat Evolved based modification that adds the units and characters of Halo: Combat Evolved back into the RTS world of which they were originally destined.
  • Call to Arms ( - Another total conversion bringing modern warfare to the Generals engine. There are four new sides, the USA, UK, United Arab Nations, and Russia, each with the most modern equipment that that country has to offer. The mod is semi-realistic, although not on the scale of True War II (
  • Red Alert: ReGeneration ( - Yet another total conversion mod, which aims to recreate the original Red Alert in the Generals engine.
  • Pro:Gen ( - A mod that adds many of the units and abilities that were cut during development back into the game.
  • Defcon ( - A future war mod that returns to the uncaring, low precision war of the past.


Main article: Doom WAD

Mods for Doom and Doom II that add or modify game content are often referred to as WADs due to using the WAD file format. The idgames archive contains over 10,000 WADs created from 1994 to present.

There also exist several Doom source ports which significantly modify the Doom engine to add support for new modes of gameplay.


Half-Life has the largest number of mods. Mods range from simple mutators to total conversions that feature extensive game engine modifications. Many mods have significantly different gameplay and features beyond thematic changes. (See List of Half-Life mods for a longer listing.)

Quake III Arena

Some impressive mods for the Quake III engine.

  • CPMA (also referred to as Promode) A competition oriented deathmatch mod, adding the best elements from all the games of the Quake series to Quake III Arena.
  • Bid For Power A Dragon Ball Z style martial arts combat game.
  • Reaction Quake 3 ( A team-based total conversion, based on the popular Quake II modification, Action Quake 2.
  • Urban Terror Team based combat with modern firearms.
  • Generations Arena ( A class-based modification in the spirit of the original Generations mod for Quake II, which allows players to fight as a character from previous id Software games using its own weapons and more.
  • DeFRaG (computer game) A mod in which you can train your trickjump skills and compete against other people by completing all kinds of parcours with this trickjump skills.
  • Epic ( An excessive clone that allows admins to change weapon firing rate, damage, projectile speed and more while still keeping the look and feel of the original excessive.

Thief (series of games)

In Thief, mods come in the form of ' fan missions'. There are over 500 fan missions currently available. Most fan missions are original in design in regards to layout of a town, the landscape, buildings, interiors, the placement of characters and items and storyline. Many include objects, characters, music and special effects that are original with the fan mission authors. A typical fan mission will take up to 4 hours to play to fulfill the mission objectives, and they are usually replayable at higher difficulty settings.

Thief: The Dark Project (1998) has about 100 fan missions available. Thief Gold (an updated version of the first) has about 40 fan missions available. Thief II: The Metal Age (2000) has over 250 fan missions available. After the release of the third game - Thief: Deadly Shadows (2004), an editor has been released and it is expected that fan missions will be created for that game as well.

A few examples of some of the best fan missions available:

  • Calendra's Cistern
  • Calendra's Legacy
  • Equilibrium
  • Gathering at the Inn
  • The Inverted Manse
  • Raid on Washout Central
  • Ranstall Keep
  • The 7th Crystal

For a complete listing of fan missions available, visit Cheap Thief Missions ( To acquire all available fan missions without having to download them, check The Keep Of Metal And Gold (

Star Wars: Knights of the Old Republic I and II

Star Wars: Knights of the Old Republic (KOTOR) modding began when a user of the StarWarsKnights forums, named Fred Tetra created KOTOR tool which allowed access and extraction of KOTOR's textures, models, scripts, etc this allowed people edit these files and create mods. KOTOR's override folder allows easy activation of these edited files because when those files are put into the override folder the folder (as the name suggests) overrides the games original files and uses the edited files if the file is the same name and type that gthe original is.

Total Annihilation

Total Annihilation is one of the most moddable games there is, with already over 2,400 custom units, one hundred mods, and a dozen custom races available for download. Some well-known TA mods and total conversions: (See List of Total Annihilation Mods for a longer listing.)

  • Absolute Annihilation ( Compilation of elements from Uberhack, XTA, GMTA, TAUIP, UTASP, Evolva and others.
  • Uberhack First and most popular mod.
  • TA Evolva Project ( Replace original TA's 3D models with more detailed ones.
  • Axis and Allies TA ( Replacing TA units with extremely accurate World War 2 units and structures.
  • Star Wars TA ( Massive Star Wars total conversion.
  • TA: Final Frontier ( Space total conversion featuring the Arm Space Navy and Corespace.
  • TA: Independence War ( Space total conversion featuring The Federation, The Corporation, The Raiders, and The Aliens.
  • The Lost Legacy ( Massive race with over 100 units
  • The Rumad Race (
  • Emergency Pack ( A pack of smart units.

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