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A gamemaster (simplify as GM, also known as game master, game manager, game moderator or referee) is a person who acts as an organizer, officiant for questions regarding rules, arbitrator, and moderator for a multiplayer role-playing game. They are most common in co-operative games in which players work together and are less common in competitive games in which players oppose each other.
The role of a gamemaster in a traditional role-playing game is to weave the other participants' player-character stories together, control the non-player aspects of the game, create environments in which the players can interact, and solve any player disputes. The basic role of the gamemaster is the same in almost all traditional role-playing games, although differing rule sets make the specific duties of the gamemaster unique to that system.
The role of a gamemaster in an online game is to enforce the game's rules and provide general customer service. Also, unlike gamemasters in traditional role-playing games, gamemasters for online games in some cases are paid employees.
 History and variants of the term
The term gamemaster and the role associated with it could be found in the postal gaming hobby. In a role-playing game context, it was first used by Chivalry & Sorcery. The term may have also been in use by Flying Buffalo in the 1975 game Tunnels and Trolls, with previous usage in a wargaming context including Guidon Games 1973 ruleset, Ironclad. In typical play-by-mail games, players control armies or civilizations and mail their chosen actions to the GM. The GM then mails the updated game state to all players on a regular basis.
Each gaming system has its own name for the role of the gamemaster, such as "judge", "narrator", "referee", "director", or "storyteller", and these terms not only describe the role of the gamemaster in general but also help define how the game is intended to be run. For example, the Storyteller System used in White Wolf Game Studio's storytelling games calls its GM the "storyteller", while the rules- and setting-focused Marvel Super Heroes role-playing game calls its GM the "judge". The cartoon inspired role-playing game Toon calls its GM the "animator". A few games apply system- or setting-specific flavorful names to the GM, such as the Hollyhock God (Nobilis, in which the hollyhock represents vanity), or the most famous of such terms, "Dungeon Master" (or "DM") in Dungeons & Dragons.
 Gamemasters in traditional role-playing games
The gamemaster prepares the game session for the players and the characters they play (known as player characters or PCs), describes the events taking place and decides on the outcomes of players' decisions. The gamemaster also keeps track of non-player characters (NPCs) and random encounters, as well as of the general state of the game world. The game session (or "adventure") can be metaphorically described as a play, in which the players are the lead actors, and the GM provides the stage, the scenery, the basic plot on which the improvisational script is built, as well as all the bit parts and supporting characters. Gamemasters can also be in charge of RPG board games making the events and setting challenges.
GMs may choose to run a game based on a published game world, with the maps and history already in place; such game worlds often have pre-written adventures. Alternatively, the GM may build their own world and script their own adventures.
A good gamemaster draws the players into the adventure, making it enjoyable for everyone. Good gamemasters have quick minds, sharp wits, and rich imaginations. Gamemasters must also maintain game balance: hideously overpowered monsters or players are no fun. It was noted, in 1997, that those who favor their left-brain such as skilled code writers usually do not make it in the ethereal gamemaster world of storytelling and verse.
 The four major "hats"
- Author: The GM plans out (in the loosest sense) the plot of the story of which the Player Characters will become heroes (or villains, or rich, or whatever); creating (or adapting, or just choosing) the setting, populating that region with villains and other NPCs, and assigning them any necessary backgrounds, motivations, plans and resources.
- Director: During the game, while each of the other players typically controls the actions of one of the Player Characters, the GM decides the actions of all the NPCs as they are needed. The GM may also direct a particular "NPC" that travels with the party (commonly known as a GMPC), but this may occasionally be open to abuse since the Game Master having a "pet" NPC may compromise his neutrality.
- Referee: In most Tabletop RPGs, the rules are supplied to resolve conflicting situations (avoiding the "Bang! you're dead!"/"No, you missed!" quandary). The GM is expected to provide any necessary interpretation of those rules in fuzzier situations. The GM may also approve or provide House Rules in order to cover these corner cases or provide a different gaming experience.
- Manager: The least officially prescribed portion of GMing, and thus the part that takes people the most by surprise. The GM is typically the one to organize the game in the first place, find players, schedule sessions, and figure out a place to play, as well as acting as a mediator and having to balance the needs and desires of all participants — sometimes having to divine the real desires of indecisive or self-deluded players.
 Gamemasters in online games
A gamemaster's duties in an online game are to act as a moderator or customer service representative for an online community. A gamemaster in such a game is either an experienced volunteer player or an employee of the game's publisher. They enforce the game's rules by banishing spammers, player killers, cheaters, and hackers and by solving players' problems by providing general customer service. For their tasks they use special tools and characters that allow them to do things like teleport to players, summon items, and browse logs that record players' activities. Gamemasters in MUDs are often called "wizards". Often, players who feel dissatisfied with the game will blame the GMs directly for any errors or glitches. However, this blame is misdirected as most GMs are not developers and cannot resolve those types of problems.
The now defunct America Online Online Gaming Forum used to use volunteers selected by applications from its user base. These people were simply referred to as OGFs by other members, and their screennames were indicative of their position (i.e., OGF Moose, etc.). While membership in the Online Gaming Forum had only one real requirement (that is, be a member of AOL), OGFs were given powers quite similar to AOL "Guides" and could use them at will to discipline users as they saw appropriate.
World of Warcraft has employees of Blizzard Entertainment that serve as gamemasters to help users with various problems in gameplay, chat, and other things like account and billing issues. A gamemaster in this game will communicate with players through chat that has blue text and they will also have a special "GM" tag and Blizzard logo in front of their names.
Miniconomy, a smaller text-based MMO has a team of Federals, experienced players that help moderate the game and interactions.
Transformice, an MMORPG, has a team of volunteer moderators called Mods who are experienced players that help moderate the game and interactions.
Note that a few games, notably Neverwinter Nights and Vampire: The Masquerade – Redemption, are video game adaptations of tabletop role-playing games that are played online with one player acting as a traditional gamemaster.
 Gamemasters in online chats
Sometimes, tabletop gamemasters simply can not find players interested in either the same setting, product line, or play style in their local neighborhood. The advent of the personal computer has brought a moderate solution to this in the form of online chat programs. This enables gamemasters to find players online, and for them to meet via chat rooms, forums, or other electronic means. This, in contrast to a normal table top game or a game meant to be played online, creates many more duties for a prospective gamemaster. It is wise to write out descriptive text ahead of time, and since the gamemaster cannot rely on his acting skills to get the personality of NPCs and monsters across, the need for music (often considered a distraction in a normal table top game) becomes much greater, as background music helps to set the mood for other players. The gamemaster must also keep hard copies of all the players' characters himself, since he can not glance at them as he would in a normal game. Moreover, all players must rely on the honor system when determining the outcome of events through dice rolls, as the die is only visible to the player who most benefits from lying about it.
There are also some benefits. The use of Wiki software can allow gamemasters to easily keep track of notes and characters that appear during play, as well as character sheets and other useful tools for the players. They may evolve into the equivalent of a home-made gaming supplement. Scripting software allows complicated mechanics that include many tables or a lot of math to be resolved at a push of the button, while teleconferencing allows the players and gamemaster to communicate through voice, video, and a shared whiteboard. The use of technology to enable online play is growing, as can be seen from products like the D&D Insider.
 See also
- Tresca, Michael J. (2010), The Evolution of Fantasy Role-Playing Games, McFarland, p. 63, ISBN 078645895X
- Wham, Tom; Lowry, Don (1973). Ironclad: Civil War Naval Rules. Belfast, Maine: Guidon Games. p. i.
- Pendleton, Jennifer. (August 18, 1997) Los Angeles Times. Trends:Nice Work If You Can Master It. Section: Business; Page 6.