The term multiplayer comes from the phrase "multiple players" and describes a game several people can play together. In some computer games, multiple players can play the same game together by connecting their computers together with a local network or by using the Internet.
GTA 1 and GTA 2 were released with multiplayer support both for the PC only, but GTA 3, GTA VC and GTA SA were not. GTA LCS and GTA VCS have multiplayer support both for the PSP only. GTA 4 is currently the only GTA that has native multiplayer support on all its platforms.
Various projects have been released or are being developed by fans of the GTA series to add multiplayer gaming to GTA 3, GTA VC and GTA SA. Some fans have created other projects to improve the multiplayer systems for GTA 1 and GTA 2.
The original Grand Theft Auto was released with a multiplayer system by DMA Design (now called "Rockstar North"), but most players find it too difficult to use. It features two gameplay modes:
- Deathmatch - players kill each other by any means. The first player to reach the required number of kills wins the game.
- Cannonball Run - players must drive through a series of checkpoints to the finish. The first player to reach the finish wins the game.
This edition allows 1-4 players in each multiplayer game.
There is a multiplayer project out called GTADS that allows users with decent ping (<150ms) to play GTA 1/London with one another. It is currently in its Beta Release 1.13.
Grand Theft Auto 2 was released with an all-new multiplayer system by Rockstar Games. It is a big improvement over GTA 1, featuring specialized multiplayer levels with new game modes. However, it is still difficult for most users to set up games, especially when trying to play on computers behind routers and firewalls.
There are three gameplay modes:
- Deathmatch - players kill each other by any means to gain "frags". If a player kills himself or herself, he or she gets one or more "frags" deducted. GTA 2 does not allow negative numbers of frags. There are two ways a Deathmatch game can end:
- A player reaches the required number of kills and wins the game.
- The time limit runs out, in which case the player with most kills wins the game. If both players have the same number of frags, the game is a draw.
- Tag - One player starts off "it", that player can't pickup weapons, can't see arrows and their car burns quickly. Whoever kills that player will then become "it". The player who has been "it" the longest when the time limit runs out is the winner.
- Points - each player tries to gain more points than the others. Points are given in the same way as the regular game, although killing another player gives a large points bonus. There are two ways a Points game can end:
- A player reaches the points limit and wins the game.
- The time limit runs out, in which case the player with most points wins the game. If both players have the same number of points, the game is a draw.
There are various fan made levels that add racing or cannonball run style gameplay. Custom levels can have new game modes but it has yet to be fully taken advantage of.
There are three projects created by fans to improve the multiplayer system in GTA 2. These projects concentrate on making it easier to find other GTA 2 players, as well create games and join games:
One of the (yet incomplete) projects focuses on the same without opening multiple ports and possibly incorporating stats in the future:
The default GTA 2 multiplayer maps support 2-6 players. Custom maps/scripts can support from 1 to 6 players.
GTA 2 uses simple tick mechanism similar to one used in GTA 1 to synchronize games. The engine was built with this in mind so that if you always use same controls, the game will always perform the same way (even random functions depend on this), so GTA 2 only transfers player key input and a tick message to advance 1 frame. Sometimes it skips frames on high latency, which means the sync is near perfect, but needs very low latency (anything below 100 - 120 ms packet roundtrip is playable). For more players sum the pings to get the latency the game will run at. This means over cable or DSL GTA 2 is playable with three or fewer players and on LAN it is easily playable with six because of low latency/ping.
Grand Theft Auto III was released without multiplayer support, it only featured single player gaming. There are hints within the game files (like menu screens) showing that multiplayer was planned to be included, but never made it into the final build of the game.
Several projects have been created by fans to bring multiplayer to GTA 3, including:
GTA Vice City was released without multiplayer support, it only featured single player gaming. Projects which have been created by fans to bring multiplayer to GTA VC include:
- gtaTournament 
- VC-MP on GTAForums
- Multi Theft Auto 
- GTALC Multiplayer 
- State Of Liberty Online 
- Vice City Online 
- Networked: VC previously known as Vice City: Players 
GTA San Andreas was released without multiplayer support, it only featured single player gaming on the PC. The PS2 and Xbox releases support a basic two player mode on one console. Projects which have been created by fans to bring multiplayer to GTA SA include:
- Inactive or canceled projects:
- Active projects:
GTA Liberty City Stories was released with multiplayer support for the PSP only but not for the PS2. It supports up to six players through WiFi ad-hoc mode.
GTA Vice City Stories was released with multiplayer support for the PSP only but not for the PS2. Similar to GTA LCS, it supports up to six players through WiFi ad-hoc mode.
Grand Theft Auto IV was released with multiplayer support on all its platforms. The PS3 and XBox 360 versions support up to 16 players online while the PC version supports up to 32 players online. There are 15 modes to choose from:
- One Man Army
- Mafiya Work
- Car Jack City
- GTA Race
- Free Mode, Party Mode
- Team Deathmatch
- Team Mafiya Work
- Team Car Jack City
- Turf War
- Hangman's NOOSE
- Deal Breaker
- Bomb da Base II
Since there are huge possibilities to make multiplayer deeper than Rockstar had created, there are teams working on an expanded multiplayer for GTA IV.
- Inactive or canceled projects:
- Active projects: