Persistent world

A persistent world is a shared, computer-simulated environment that keeps existing, and keeps its state, when the people using it log off. Richard Bartle, co-author of the first MUD, wrote in his 2003 book Designing Virtual Worlds that a virtual world's environment "continues to exist and develop internally (at least to some degree) even when there are no people interacting with it; this means it is persistent". In a 2010 history of the form he gave a shorter test: "if you stop playing then come back later, the virtual world will have continued to exist in your absence".

Several definitions of virtual worlds use persistence to separate them from ordinary multiplayer games. A first-person shooter match or a game show ends and starts again from scratch, while a persistent world such as a MUD or a massively multiplayer online role-playing game (MMORPG) keeps at least part of its state between sessions and across server restarts. In virtual reality, the same questions arise for social VR platforms and VR MMOs, which decide what world and player data to keep between sessions. In augmented reality, a related use of the word describes virtual content that stays fixed to a real place across sessions, users and devices, usually through spatial anchors and shared cloud maps.

Reviewed 6 October 2026. Checked every quotation, date and number against Bartle 2003/2010, Nevelsteen, Vaz Salles et al., Guo et al., Scargill et al., Massively, CCP, VRChat, ARCore, ARKit, Meta, Magic Leap, Microsoft and news sources; DOIs confirmed via Crossref. About review dates.

Definition

Bartle's 2003 list of the conventions that most virtual worlds share ends with "The world is (at least to some degree) persistent." He contrasted virtual worlds with neighboring forms: "a single-player game is not shared; a first-person shooter isn't persistent." In 2009 the MMO news site Massively described its own "persistence test" for deciding which games to cover, and summed up the ideal as "One persistent world holding thousands of players simultaneously, a world that continues even when you log off." By that test the Xbox Live game show 1 vs. 100 failed, although more than 70,000 people could play it at once, because "game shows are never persistent. Contestants change, games reset, and new prizes are made available to be won."

Kinds of persistence

Kim J. L. Nevelsteen, then of Stockholm University's Department of Computer and Systems Sciences, built a technical definition of a virtual world by applying grounded theory to sample technologies, and split persistence into separate properties.

Term	Meaning in Nevelsteen's analysis
World persistence	The world "continues to exist and is available to the players when they want to access it" (Bartle's criterion)
Data persistence	World data is not lost if the system fails; it applies to "all data spaces that hold non-ephemeral data"
Game world persistence	Events and activities in the game world that do not "reset" and are not interrupted by real-world events; Nevelsteen treated it as a cultural rather than technical property
Pseudo-persistence	Persistence that is simulated "without raising awareness to the player", for example by scheduling play times around down times or by loading world data only when the players who need it are online

Nevelsteen argued that Bartle's 2003 wording, which required the world to "develop internally" without players, is superior to the 2010 version, because a world can be kept in existence through player interaction alone, which only simulates world persistence. In his analysis, the only properties that seemed to separate video games from virtual worlds were that a virtual world cannot be paused and that it persists; since some games could be said to meet the first, he quoted Carina Girvan's description of persistence as the "defining characteristic with which to distinguish between video games and virtual worlds".

Degrees of persistence

Bartle treated persistence as a matter of degree: it "relates to the amount of a virtual world's state that would be retained intact were the whole system to be shut down and restarted." Every virtual world persists something, he wrote, but what it persists varies.

What survives a restart	Examples given by Bartle (2003)
Initial state of the world plus records for individual player characters	AberMUDs
The above plus what characters were carrying	DikuMUDs
Certain classes of objects, such as player characters' corpses	EverQuest
The entire world state	Ultima Online
The entire world state plus all incrementally added functionality	MOOs

Bartle noted that saving more state costs time and storage, but said this was not the usual reason designers chose a low degree of persistence. Adventure-style worlds often contain multi-stage puzzles with world-wide effects ("you can't unlaunch a rocket or unexplode a bomb"), and designers want to reuse that content for many players; "Full persistence in this situation would be a bad thing, because persistence is all about not reinitializing." Comparing worlds on a grid of persistence against who is allowed to build, he found that "the more people who can add content directly to a virtual world, the more of that world will tend to persist."

How it works

Server state and storage

In a 2009 study for the VLDB conference, Cornell University researchers Marcos Vaz Salles, Tuan Cao, Benjamin Sowell, Alan Demers, Johannes Gehrke, Christoph Koch and Walker White described MMOs as "persistent virtual worlds" that, unlike single-player games, "must persist across user sessions": players expect their achievements to be reflected when they rejoin, and losing player data in a crash is unacceptable. The core of such a game is a simulation loop running at about 30 or 60 Hz; to keep up, the active game state is held in the server's main memory, and "Disks are used only to provide persistence or to store information about inactive (e.g., logged off) characters." Updates that need full transactional guarantees, such as item trades, go to a standard database back end, while far more frequent updates such as character movement are handled inside the simulation. The authors cited EVE Online as processing nine million item insertions per day that required transactional behavior, and recommended that MMO developers checkpoint game state with a copy-on-update scheme and a double-backup disk organization.

Bartle described the same pattern in 2003: a world runs on a cluster of sub-servers that have access to "a shared character database that stores the persistent data relating to players' characters", and large worlds usually keep a separate database for environment data.

Shards, regions and instances

Operators split large worlds to handle load. Nevelsteen distinguished two methods. With regions, the space is divided into areas served by different groups of servers, but players can still move through all of it. With shards, players are assigned to separate copies of the world that "do not synchronize with each other", and they cannot move between them. An instance, such as a dungeon created for one group's run, can be treated as a temporary shard. In World of Warcraft, each realm is a shard; later updates let players from different realms play the same instance dungeon together, with the results synchronized to each player's own realm, while the realms themselves still do not synchronize with each other. Bartle reported that EverQuest reached 40 server clusters in 2000, averaging around 1,500 simultaneous players on each at peak time.

EVE Online, developed by CCP Games, runs all players in a single shard. In an article first published in Game Developer magazine, the CCP team wrote that "a single shard should be the natural choice of any MMO developer" because players are the main content, and a single shard gives them "a shared history as a whole society rather than a disjointed one based on smaller server populations." All data is read from and written to "a single database that binds the whole world together", and CCP said the main bottleneck was database I/O, which led it to move the entire database to solid-state drives. According to Nevelsteen, EVE Online is one shard that is statically divided into regions, with one server process per solar system.

Resets and pseudo-persistence

Worlds that do not persist their full state reintroduce content through resets. Bartle described two approaches. In a sudden reset, the region (usually the whole world) is closed and reinitialized; this "is sometimes referred to as the Groundhog Day approach, because players relive the same day repeatedly". In a rolling reset, content such as monsters is put back piecemeal while the world stays open, a process usually called spawning or respawning. Rolling resets, he wrote, support "much higher degrees of persistence".

Nevelsteen used pseudo-persistence to describe online games that only imitate a persistent world. He classified multiplayer Diablo, where players gather in a lobby and then play dungeon instances that are created for one run and reset, as pseudo-persistent. Summarizing a 2015 Game Developers Conference talk by Justin Truman, he described Destiny as a universe of instances called "bubbles", each supporting six players and twenty-five software agents, with a "WorldServer" that persists all character and progression data in the cloud. He concluded that Destiny was still only pseudo-persistent, because the bubbles themselves are copies of space that lack persistence.

History

The first MUD was written by Roy Trubshaw in MACRO-10 on a DECsystem-10 at the University of Essex in autumn 1978; when Trubshaw left Essex, Bartle took over full control of the game. In his 2010 history, Bartle wrote that the PLATO game Avatar (1979) had all the features expected of a virtual world except that "Its only failing is in its poor persistence, but then MUD1 was only marginally better in that regard." He described the earlier Oubliette (1977), which Avatar was created to beat, as "not truly persistent". In Designing Virtual Worlds he wrote that Oubliette "had persistent characters, but was not a persistent world."

The phrase itself was used as a genre label. According to Bartle, when graphical worlds appeared, "At first the new games were called persistent worlds, but when the enormous numbers of simultaneous players they were attracting became their defining feature this changed to MMORPGs". Researchers kept persistence in their definitions of virtual worlds; it appears in Mark W. Bell and Sarah Robbins-Bell's 2008 definition ("a synchronous, persistent network of people, represented as avatars, facilitated by networked computers") and in Bartle's 2010 definition of a virtual world as "an automated, shared, persistent environment".

Persistent worlds in VR and AR

Headset-based worlds

Bartle separated the two ideas in 2003: virtual reality "is primarily concerned with the mechanisms by which human beings can interact with computer simulations", while the attraction of a virtual world is "what awaits when they enter a virtual world, not the means by which they do so." Nevelsteen likewise noted that only some VR environments meet the definition of a virtual world. Headset-based multi-user platforms show the same design choices as earlier online worlds.

VRChat runs each world as separate instances, which its official wiki describes as "unique sessions for a world"; users in one instance can see and interact with each other but not with users in other instances of the same world. Instances may run for up to seven days, and long-running instances reset automatically. On 21 November 2024 VRChat added a Persistence feature to its Udon scripting system with SDK 3.7.4, which "allows you to build VRChat worlds that store data between sessions". It offers two kinds of per-player storage: PlayerData, a key-value store, and PlayerObjects, objects created for each player whose synced variables can be made persistent. Each world may store 100 KB of PlayerData and 100 KB of PlayerObject data per player on VRChat's servers, and the data is available on all platforms and in all instances of the same world.

The VRMMO Zenith: The Last City uses shards. When Ramen VR stopped new development in July 2024, the studio said it would "keep Zenith: The Last City and Zenith: Infinite Realms shards running for the foreseeable future".

Several social VR platforms have closed. Microsoft shut down AltspaceVR on 10 March 2023 and advised users to download their data before that date. Rec Room announced on 31 March 2026 that the platform would go dark on 1 June 2026; from the announcement, no new accounts or friend requests could be made and creators could no longer share monetized content.

Persistent AR content

In augmented and mixed reality, "persistent" usually refers to virtual objects that reappear in the same physical place in a later session or on another device. Scargill, Chen and Gorlatova wrote in 2021 that the most common type of AR experience was then "single-session", meaning that "virtual content does not persist once an application is closed", and that keeping holograms in place across sessions with spatial anchors depends heavily on visual conditions and on their consistency "over multiple days, weeks or months". The major platforms provide this through anchors and saved maps; the spatial anchor and AR Cloud articles cover the mechanisms in detail.

Platform	Persistence mechanism
ARKit (Apple)	ARWorldMap, available from iOS 12, saves ARKit's map of a space; an app can restore it later and use its anchors "to place the same virtual content at the same positions from the saved session, if the app launches in the same physical environment"
ARCore (Google)	Cloud Anchors "can be used to persist AR experiences in the real world" and share them across Android and iOS devices; a hosted anchor's lifetime is set in days, up to 365 days with keyless authorization or one day with an API key; visual data uploaded when hosting is discarded within 24 hours
Meta Quest (Meta Horizon OS)	The Anchors API lets an anchor's position "be persisted and discovered across sessions and shared with other users, both synchronously and asynchronously", with storage on the device or on Meta's servers
Magic Leap 2	Anchors stored on the device are available for multiple sessions in the space where they were created; in AR Cloud mode they can be reached from different devices localized to the same space; each anchor has an expiration timestamp; Magic Leap deprecated AR Cloud on 22 January 2025, and its configuration instructions now cover only customers who bought an Enterprise license with AR Cloud before that date
Azure Spatial Anchors (Microsoft)	Cloud anchor service whose lifecycle ran from 25 February 2019 until its retirement in November 2024
visionOS 26 (Apple Vision Pro)	"Persistence lets widgets and windowed apps stay where you placed them, even if you restart your Apple Vision Pro"; released 15 September 2025

When the widget system was announced in June 2025, Road to VR reported that Vision Pro windows "will relocate when the headset is recentered or rebooted", while the new widgets "will always stay in that place, even if the headset is restarted."

Research

Academic work on persistent worlds spans game studies, databases and human-computer interaction. Bartle's Designing Virtual Worlds analyzed persistence as a design dimension alongside who is allowed to change the world, and set out the sudden and rolling reset strategies. Nevelsteen's grounded-theory definition, published in Computer Animation and Virtual Worlds, separated world, data and game world persistence and introduced pseudo-persistence to classify games that only imitate it; he also concluded that the metaverse "will be necessarily mixed", in the sense of mixed reality. The VLDB study by Vaz Salles and colleagues treated MMO persistence as a database durability problem and compared checkpoint recovery algorithms in a simulation model fed with update traces generated synthetically and from a prototype game server.

For AR, Guo, Canberk, Murphy, Monroy-Hernández and Vaish built Blocks, an iOS app whose collaboratively built structures "persist, i.e., they do not disappear from session to session", tied either to a physical location or available anywhere. A back end maintained the state of users, maps and blocks, and the app preserved each block's position, size, color and ownership over time. In a three-day field study on a company campus, 68 participants used it in 222 sessions and added 6,970 blocks, and one participant said location-specific blocks added "a magical element of there being a persistent world taking place in parallel to what you see all day." Scargill and colleagues limited their measurements of hologram stability in smartphone AR to single sessions, and said they were adapting the method to measure holograms designed to persist across sessions with spatial anchors.

See also

• Virtual world
• Metaverse
• Social VR
• VRMMO
• Spatial anchor
• AR Cloud
• Mirror world
• Collaborative virtual environment