Games that can only be played while connected to a wide area network like the internet. All online games have two necessary components: a server and a client computer, with larger games having multiples of each, though usually the number of client computers is far greater than servers.
Many games throughout the history of gaming have been exclusively online. The earliest form of online games are arguably the Play-by-Post Games, originally referring to snail-mail and covering games such as Chess; they moved online with the advent of email and forum servers, the quicker response times and computer automation let to text-based muliti-player games like the Multi-User Dungeon (M.U.D.), related to the single-player Interactive Fiction. As computer graphics expanded into 2D and 3D rendering, video-games had wildly varying limits on the maximum amount of players in a single virtual-space, with newer games trending towards smaller groups as hardware development was focused on graphics-quality.
This changed with the development of Massively Multiplayer Online games, or M.M.O.s for short, showcasing large numbers of players beyond typical multi-player gaming for LANs. One way this is accomplished is by having multiple servers, each hosting a different section of the in-game world. MMOs started with the Role-Playing Game genre and have since branched out to others, including First-Person Shooters and Real-Time Strategy genres.
- MMOG (Massively Multiplayer Online Game; more commonly abbreviated as MMO)
- MUD (Multi-User Dungeon)
- Play-by-Post Games
- Virtual Worlds
- Web Games