A Massively Multiplayer Online Game (also called MMOG or
MMO) is a computer game which is capable of supporting hundreds
or thousands of players simultaneously. By necessity, they are played on
the Internet, and feature at least one persistent world. Some argue that
small player-count games, with 200 and fewer players, are also part of
the genre; the persistent world is probably the only "hard" requirement.
MMOGs can enable players to cooperate and compete with each other on a
grand scale, and sometimes to interact meaningfully with people around
the world. They include a variety of gameplay types, representing many
video game genres. Many MMOGs require players to invest large amounts of
their time into the game. Most MMOGs require a monthly subscription fee,
but some can be played for free.
There are a number of factors shared by most MMOGs that make them
different from other types of computer games. MMOGs create a persistent
universe where the game continues playing regardless of whether or not
anyone else is. Since these games strongly or exclusively emphasize
multiplayer gameplay, few of them have any significant single-player
aspects or client-side artificial intelligence. As a result, players
cannot "finish" MMOGs in the typical sense of single-player games. Some
MMOGs, such as Star Sonata, do have an end condition that
includes awarding a "winner" based on a player's standing in the game at
Most MMOGs also share other characteristics that make them different
from other multiplayer online games. MMOGs host a large number of
players in a single game world, and all of those players can interact
with each other at any given time. Popular MMOGs might have thousands of
players online at any given time, usually on a company owned server.
Non-MMOGs, such as Battlefield 1942 or Half-Life usually
have less than 50 players online (per server) and are usually played on
private servers. Also, MMOGs usually do not have any significant mods
since the game must work on company servers. There is some debate if a
high head-count is the requirement to be a MMOG. Some say that it is the
size of the game world and its capability to support a large number of
players that should matter. For example, despite technology and content
constraints, most MMOGs can fit up to a few thousand players on a single
game server at a time.
To support all those players, MMOGs need large-scale game worlds, and
servers to connect players to those worlds. Sometimes a game features a
universe which is copied onto different servers, separating players, and
this is called a "sharded" universe. Other games will feature a single
universe which is divided among servers, and requires players to switch.
Still others will only use one part of the universe at any time. For
example, Tribes (which is not an MMO) comes with a number of
large maps, which are played in rotation (one at a time). In contrast,
the similar title PlanetSide uses the second model, and allows
all map-like areas of the game to be reached via flying, driving, or
MMORPGs usually have sharded universes, as they provide the most
flexible solution to the server load problem, but not always. For
example, the space sim Eve Online uses only one large cluster server
peaking at over 32,000 simultaneous players.
There are also a few more common differences between MMOGs and other
online games. Most MMOGs charge the player a monthly or bimonthly fee to
have access to the game's servers, and therefore to online play. Also,
the game state in an MMOG rarely ever resets. This means that a level
gained by a player today will still be there tomorrow when the player
logs back on. MMOGs often feature ingame support for clans and guilds.
The members of a clan or a guild may participate in activities with one
another, or show some symbols of membership to the clan or guild.
However, the boundaries between multiplayer online games and MMOGs
are not always as clear or obvious. (2002) and Diablo II are
usually called online role-playing games, (RPGs) but are also sometimes
called MMORPGs (a type of MMOG).
Information Courtesy of