This article is about a type of online computer game. For other uses of the word "mud," see mud

In computer gaming, a MUD (multi-user dungeon, dimension, or sometimes domain) is a multi-player computer game that combines elements of role-playing games, hack and slash style computer games, and social instant messaging chat rooms. Typically running on a bulletin board system or Internet server, the game is usually text driven, where players read descriptions of rooms, objects, events, other characters, and computer-controlled creatures or non-player characters (NPCs) in a virtual world. They may interact with each other and the surroundings by typing commands that resemble a natural language, usually English.

Traditional MUDs implement a fantasy world populated by elves, goblins, and other mythical beings with players being able to take on any number of classes, including warriors, mages, priests, thieves, druids, etc. The object of the game is to slay monsters, explore a world rich in fantasy and with adventure, and to complete quests. MUDs are typically fashioned around the dice rolling rules of the Dungeons & Dragons (D&D) series of games.

MUDs typically have a fantasy setting, while others are set in science fiction-based universe. Still others, especially those which are based on MOOs, are used in distance education or to allow for virtual conferences. MUDs have also attracted the interest of academic scholars from many fields, including communications, sociology, law, and synthetic economies.

Most MUDs are run as hobbies and are free to players; some may accept donations or allow players to "purchase" in-game items.

The first MUDs appeared in 1977 on the PLATO system, and their popularity escalated in the USA during the 1980s, when (relatively speaking) cheap, home personal computers with 300 to 2400 baud modems enabled role players to log into multi-line BBSes. Roguelike games were also becoming popular at that time. In Europe at around the same time, MUD development was centered around academic networks, particularly at the University of Essex where they were played by many people, both internal and external to the University. In this context, it has been said that MUD stands for "Multi-Undergrad Destroyer" due to their popularity among college students, and the amount of time devoted to the MUD by the student.

The very first MUD was Oubliette, written by Jim Schwaiger, and published on the PLATO system in 1977. It was so difficult that one could not play it alone: in order for players to survive, they had to run in groups. The second MUD was also on PLATO, a game called 'Moria,' written in 1977, copyright 1978. Again, players could run in parties but in this MUD it was also possible to effectively play while only running one character.

Early MUDs from England were created in 1978 by Roy Trubshaw and Richard Bartle at Essex University on a DEC PDP-10 in the UK [1]. They chose the acronym MUD to stand for Multi-User Dungeon, and was designed to be a multi-user version of another PDP-10 game called Dungeon (or DUNGEN due to the six character filename limit), which was later commercially released by Infocom under the original development code name Zork. Zork in turn was inspired by an older text-adventure game known as Colossal Cave Adventure or ADVENT. The classic game MIST (also part of Essex University MUD) which could be played from any computer connected to JANET (a European academic network predating the internet), became one of the first of its kind to attain broad popularity.

Another early MUD was Avatar, written in 1979 by Bruce Maggs and Andrew Shapira, both high school students using the PLATO system at the University of Illinois. This MUD was 2.5-D game running on 512x512 plasma panels of the PLATO system, and groups of up to 15 players could enter the dungeon simultaneously and fight monsters as a team.

In the early 1980s Alan E. Klietz wrote a game called Milieu using Multi-Pascal on a CDC Cyber, which was used by high school students in Minnesota for educational purposes. Klietz ported Milieu to an IBM XT in 1983, naming the new port "Scepter of Goth" (also spelled "Sceptre of Goth"). Goth supported 10 to 16 simultaneous users, typically connecting in by modem. Scepter of Goth was one of the first commercial MUDs, as franchises were sold to a number of locations. Scepter (as well as unfinished advanced MUD by Klietz called ScreenPlay) was first owned and run by GamBit (of Minneapolis, Minnesota), founded by Bob Alberti. GamBit's assets, including Scepter and ScreenPlay, were then sold to InterPlay (of Fairfax, Virginia). InterPlay eventually went bankrupt, making Scepter no longer available. In 1984, Mark Peterson wrote "The Realm of Angmar", beginning as a clone of Sceptre of Goth.

A version of MUD is still running at www.british-legends.com and versions of its descendant MUD2 run at www.mud2.com and www.mudii.co.uk. Two versions of Avatar, one from ~1979 and one from 1984, are still running at www.cyber1.org. Moria is also available, but the system owners have yet to be able to procure a working copy of Oubliette.

These text-adventure games (both single and multi-player) drew inspiration from the paper-and-pencil based role-playing games (RPGs) such as Dungeons & Dragons which were approaching their peak popularity at this time, especially with the release of Advanced Dungeons & Dragons (AD&D) in 1977.

This strong bond between RPGs and MUDs continued through the years with the release of dozens of AD&D modules and series of related books and stories (i.e. Forgotten Realms and Dragonlance). Influences also came from the gamebooks such as Fighting Fantasy, Choose Your Own Adventure and Lone Wolf, and also other RPGs such as Vampire: The Masquerade, and Middle-earth Role Playing (or MERP).

Other MUDs that appeared around 1985 included Mirrorworld, run by Pip Cordrey and developed and written by Tim Rogers, Lorenzo Wood and Nathaniel Billington, and SHADES. SHADES was a commercial MUD accessible in the UK via the Prestel system. Mirrorworld was the first MUD to feature rolling resets.

Another popular MUD was AberMUD written in 1988 by Alan Cox, also known as Anarchy, named after the University of Wales Aberystwyth. Avalon, the Legend Lives, started in 1989, was the first MUD to combine a consistent fantasy story-line with a commercial venture.

In 1989, TinyMUD introduced the ability for the players to easily participate in creating the online environment, as well as playing in it. The TinyMUD code spawned a number of descendants, including TinyMUCK and TinyMUSH, which added more sophisticated programmability. (MUCK versions 2 and higher contain a full programming language named MUF, or Multi-User Forth, while MUSH greatly expanded the variety of commands and functions available and allowed them to apply to all objects.) Some use the term "MU*" to refer to TinyMUD, MUCK, MUSH, MUSE, MUX, and their kin; others simply allow the term "MUD" to apply universally. "MUVE" is a recent coinage, intended to stand for Multi-User Virtual Environment. UberMUD, UnterMUD, and MOO are some other MUD servers that were at least partially inspired by TinyMUD but are not direct descendants.

Also in 1989, and inspired by TinyMUD and AberMUD, LPMud was developed as a more game-oriented MUD that allowed participants to program the behavior of its "monsters."

In 1991, the release of DikuMUD, which was inspired by AberMUD, lead to a virtual explosion of hack-n-slash MUDs based upon its code. DikuMUD inspired several derivative code bases as well, including CircleMUD, Merc, ROM, NiMUD and SMAUG.

In 1994 Peterson had again rewritten his game to be compatible with MS-DOS (the basis for many dial-in BBS systems), and renamed it Swords of Chaos. For a few years this was a very popular form of MUD, hosted on a number of BBS systems, until widespread Internet access eliminated most BBSs.

Though seeing some decline in the past few years due to the advent of graphical MUDs and other networked games, the MUD scene is still very much alive on the Internet, and can be accessed via standard telnet clients, or specialized MUD clients that give a more pleasant user experience. Anyone wanting to play these games online can find them listed at various web portals such as the ones in the external links section of this article.

A graphical MUD is a MUD that uses computer graphics to represent parts of the virtual world and its visitors. The foremost of these is Habitat, written by Randy Farmer and Chip Morningstar for Lucasfilm in 1985. Graphical MUDs require players to download a special client and the game's artwork. They range from simply enhancing the user interface to simulating 3D worlds with visual spatial relationships and customized avatar appearances.

After the increase in computing power and Internet connectivity during the late nineties graphical MUDs became better known as MMORPGs (massively multiplayer online role-playing games). Unlike earlier MUDs, most MMORPGs are commercial ventures. See list of MMORPGs for examples of this type of game.

A lesser known variant is the talker, typically based on ew-too, summink, sensi-summink, playground, and plenty of other code bases. The talker is essentially a MUD, with most of the complex bits of code stripped away, leaving just the communication level commands -- hence the name talker. People who use these tend to be called spods. The spod tends to be something of a long-term fanatic. Where many mudders may move on after a year or two, people who use talkers typically have been doing so for a decade or more. Talkers are significantly easier to run than an average MUD, since they don't incorporate very much artificial intelligence, and they are usually much more user friendly, since there is not often much fighting as a focus. In other words, whole families of husbands, wives, children, and siblings have been known to spod in certain circles. They also use very little network traffic, and use simple protocols, making them ideal for setting up quietly at work. Talker applications predate MUDs by many years, although some of the early ones were used to play Dungeons & Dragons over computer networks. Talkers and some other MUDs use InterMUD to chat with users on completely separate MUDs.

The spod has earned a place in the Jargon File.

Another lesser known variant of a MUD are RPI MUDs, Role-Play Intensive Multi-User Dungeon. RPI MUDs center themselves around playing out specific roles as if the role were real. Realism is often blended in with fantasy in these types of MU*s. In general, the objective of the game is not to complete computer-generated quests or to hack-and-slash monsters in order to gain levels and equipment, but to collaborate with fellow players to create complex and multi-layered storylines in a cohesive gameworld. RPIs are very different from other MU* because of this.

The majority of RPI MUDs are levelless and classless, focusing instead on skills and crafts that players may pursue during the lifetime of their characters. RPI's tend to focus more on role-playing against the world or environment, often going as far as to request their players to engage in role-play with inanimate creatures and objects. OOC (Out of character) communications are often restricted. This contrasts with other forms of mud role-playing styles such as storytelling and freestyle mushes in which role-play is conducted between players and OOC communications are more important.

RPI MUDs could be considered giant plays where the setting or world is the theater, and the players are the actors as well as the viewers. RPIs are a newer branch of MUDs in general, but have still been around for a long period of time.

The term Complex Combat MUDs covers a wide variety of games. Generally, it means that a game does not have an automated 'kill' system - rather, there is a system of balances which require user input. When coupled with an 'affliction' or 'stancing' system or some sort of tactical fighting mechanism, this is a very engaging and exciting way of doing combat. Avalon is said to be the first MUD to implement such a system, but this has been taken up by many other games since.

Another distinguishing factor of Complex Combat MUDs is that they sometimes allow client-side triggers and scripting (often considered an unfair advantage in other games), since the 'balance' system ensures that writing a script to handle fighting would be extremely difficult, but some more basic scripts make fighting more exciting for both participants, and add an extra dimension to combat.

• Category:MU* servers
• Category:MU* games
• MUD client
• Mobile (MUD)
• MUSH
• For an academic look at MUDs, see Sherry Turkle's writings
• MMORPG – Massive Multiplayer Online RPG
• MOO

• mudlists.com: Large selection of available online RPGs
• Mud Connector.com: Extensive list of available MUDs
• Top Mud Sites: Ranking of the most popular MUDs
• Some history and reviews from Richard Bartle's "Interactive Multi-User Computer Games" report
• Confessions of an Arch-Wizard Mud History: Michael Lawrie's account of the early years of MUD and MIST
• Virtual(ly) Law: The Emergence of Law in LambdaMOO
• Intermud Protocols: Information about most intermud protocols
• Intermud.org: Information about the I3 and IMC2 intermud communication protocols
• Mud Magic.com: MUD software downloads, discussion, game listings, and documentations.
• ftp.game.org: Hierarchal archive of MUD source code
• The MUDline: A timeline of MUD history.
• Mapping MUDs: 3-Dimensional modelling of a MUD
• The Gaming Center: one of the largest free gaming based bulletin board systems in existence today.
• Early MUD history
• A Classification of MUDs by Martin Keegan, Grandmaster Data Services Ltd, Cambridge, U.K.
• Erwin S. Andreasen: Home of the MUD Personality Test, 16k MUD competition, and other resources.
• Taiwan Mud List: A watch list about informations, status of Taiwan Muds.