Canon

Canon refers to the "official" parts of a story. Here, it refers to facts (events, characters, locations etc.) that are considered to "officially" appear in the GTA universe.

Description
The games within an Era are considered to share one general storyline and universe. For example, the games within the 3D Universe all share canon, with interconnecting storylines. Whilst there are overlaps between eras (e.g. Liberty City in 3D Universe and Liberty City in HD Universe), these are taken to be influences rather than the same thing.

Each universe can be considered a completely separate 'canon' of places, people, and events that exist in the same universe. Locations that appear in multiple universes are completely rebuilt, rather than just updated. Each successive universe the franchise and may  the "canon" established in a previous universe. A previous universe would be like a mythical universe that never really existed and is treated as such (e.g. Grove Street Families in GTA V). However, some things do appear in multiple universes, including company brands, vehicles, placenames, weapons, and in-series celebrities (e.g Lazlow, Fernando Martinez, Cris Formage and other radio station characters).

Player's Choices
Whilst canon is easy to define in books and films, computer games are more tricky, as the exact sequence of events is different every time it is played. For example, there may be a choice of which mission to proceed to next, or different people may be killed in a shootout. Some missions may fail if a vital character is killed, allowing it to be replayed until they survive; whilst others will allow the character to completely die and not appear in later missions.

In Grand Theft Auto IV, the story includes choices that the player can make, which significantly alter the storyline, such as whether to kill a character or let them survive. This is all treated as canon, but with multiple options available.

Grand Theft Auto V also includes player-determinated choices in certain missions and three different endings for the storyline. However, unlike GTA IV, most choices regarding optional deaths are only treated as canon if the mission objectives tells/encourages the player to do it, as in the most recent content updates in Grand Theft Auto Online, set years after Grand Theft Auto V, most of the characters that were optionally killed in the previous game appeared alive and a few years older (e.g. Lacey Jonas, Simeon Yetarian, Patrick McReary, Tyler Dixon etc). In two instances, GTA Online has also confirmed that only one of the three possible endings in GTA V is canon, even mentioning the events of said ending.

The events of each content update of Grand Theft Auto Online were also proven to have canonically happened in order of release date, no matter what order the player decides to play them. This is shown at various moments in the game's story:
 * English Dave referencing Solomun's introduction mission from the After Hours update (2018) during the The Cayo Perico Heist update (2020).
 * Kenny Dixon Jr. mentioning the Pacific Standard heist from the Heists update (2015; set in 2013) and The Diamond Casino Heist from the eponymous content update (2019) during the Los Santos Tuners update (2021).
 * DJ Pooh mentioning the scene where him and Dr. Dre found out his unreleased music was stolen in the introduction of The Cayo Perico Heist update (2020), during the The Contract update (2021).

Canonicity of Grand Theft Auto Online to the HD Universe
Grand Theft Auto Online has been confirmed to be canon to the HD Universe since its original release in 2013. Many of the events that happened in the game's original contact missions were mentioned during the events of Grand Theft Auto V, such as working for Lamar and Lester, and killing witnesses for Martin Madrazo. As the game releases updates, the timeline of the game is currently moving in real-life timing, with each new update being set in its year of release. Recently, with the release of The Contract update in 2021, the developers have also confirmed what is the official aftermath of Franklin Clinton's story, eight years after the events of GTA V, and the game's canon ending.

As a story-driven online multiplayer game, all player-created characters share the exact same story. However, storywise, the GTA Online Protagonist is only one canon character following one story, while the other surrounding players are only treated as random friends/enemies. Both character genders are treated as canon, as the game has some dialogue referring to them as either male or female, but mainly the pronoun "they" is used.

During missions, the Host takes the role of the "protagonist", while the players they have invited take the role of their "associates". If a player who owns a property (a Nightclub, for example) visits someone else's property of the same type and/or location, the characters inside will act like they never met the player (example: Lazlow calling the player a "weirdo" or "a nobody" in the Nightclub).

In certain Freemode missions, including Business Battles and Heist Preparations, the other players in the session will take the role of the player's rivals.

With the 2017 The Doomsday Heist update, players raised doubts about the canonicity of GTA Online to the HD Universe due to the addition of futuristic elements to the story, including flying cars, an AI trying to overtake the humans, and the player saving the world from a missile launch; despite many of these events having previously happened in the Grand Theft Auto series, with the GTA London Protagonist saving the whole of Great Britain from an intercontinental ballistic missile launch, and a cult of Domestobots operating independently around Bone County in Grand Theft Auto: San Andreas.

The player's properties are sometimes referred to as being unique in the dialogues, meaning that in terms of a story and narrative, there is only one existing Terrorbyte designed by Paige Harris that stores one Oppressor Mk II, only one existing Kosatka operated by Pavel, only one Celebrity Solutions Agency owned by Franklin Clinton, only one Nightclub operated by Tony Prince, etc.

While the havoc caused by players in Freeroam is not necessarily treated as canon, there are many meta-jokes in the storyline that will refer to those players, such as Pavel referring to the "people on the flying bikes" and KDJ mentioning "people chasing each other in rockets".

Anachronism and Oversights
The Luigi's Sex Club 7 appearance in the Grand Theft Auto: San Andreas short film "The Introduction" is a chronological error, as in 1998 (the setting of Grand Theft Auto: Liberty City Stories), the club is known as Paulie's Revue Bar, while when it is shown in The Introduction (set in 1992), it is still known as Sex Club Seven. The reason for this is because GTA Liberty City Stories was developed after GTA San Andreas.

There are many instances in the series where a location that should exist in one period of time does not appear, for example, Maisonette 9 and Hercules nightclubs not appearing in GTA IV despite being set at the same time as The Ballad of Gay Tony, Benny's Original Motor Works not appearing in GTA V, despite GTA Online: Lowriders being set shorty before GTA V, or the Mount Chiliad Launch Facility entrance not appearing in GTA V despite dialogue saying it was built during the Cold War in the 1960s.

Non-Canon
Unofficial modifications are not canon - this could include adding in characters/vehicles that don't exist in the GTA universe (at that time), missions that never occurred, or granting access at different stages of the game. Some fans write missions and stories that are not canon, and these are referred to as Fan Fiction.