Data Worlds are worlds made from data that exist within realms known as Datascapes. A data world may be created using data from a real world, thus creating a digital replica of that world such as those produced by Jiminy's Journal or the Book of Prophecies, or may be programmed to be unique such as The Grid or Game Central Station. Datascapes were first described in Kingdom Hearts III Glossary.
Data worlds cannot be reached via Gummi ship as they usually exist within computers, so can only be accessed via an interface within the world that contains them. However, there are some exceptions to this. Ansem the Wise was able to store data containing a replica of Destiny Islands in Sora's heart, during his memory recovery in Twilight Town, which Riku accesses during his Mark of Mastery exam. Axel was also able to gain access to the simulated Twilight Town via a portal from the real world, and Sora later used this same connection to reach The World That Never Was.
Data itself also plays an important role in the Kingdom Hearts universe, as it allows for the creation and manipulation of certain situations and environments. The Mirage Arena uses data to generate enemies to battle as well as to connect people via the internet. Likewise, the Garden of Assemblage in Radiant Garden and Cid's recreation of it can be used to create data replicas of both Organization XIII and Real Organization XIII to battle. Ansem the Wise attempted to digitize Xemnas's Kingdom Hearts and store it as data in the Kingdom Hearts Encoder, but the process proved too much and his machine exploded, damaging Kingdom Hearts and sending Ansem to the Realm of Darkness.
The Master of Masters used the Book of Prophecies to create projections of the futures of worlds connected to Daybreak Town, in order for the Unions to gather Lux. After the Keyblade War, the worlds became separated from Daybreak Town, so they were recreated using their data in order for them to still be reached. A virtual Daybreak Town was created to connect the real Daybreak Town with the data worlds. The Unions would continue to live in the real Daybreak Town and access the data worlds via the virtual one. However, when Game Central Station is forcibly connected to Daybreak Town and caused glitches to appear everywhere, Brain begins to wonder if they are actually in the real Daybreak Town or the virtual one.
After Sora defeated her, Maleficent from the future manages to travel back in time to the Enchanted Dominion and attempts to change her fate, but is defeated once more. Afterwards, she discovers from Darkness that she is in a data version of the world. The Master of Masters purposefully refrained from making the world real in order to trap Maleficent and prevent her from changing what was written in the Book of Prophecies. She learns from Darkness that she can return to her own time by first escaping the datascape, which she can accomplish if she accesses the control room in the virtual Daybreak Town's clock tower. With Darkness's help, Maleficent gains access to the Ark and after a confrontation with Lauriam, uses one of the Lifeboats to return to the real world with Darkness. In the real Daybreak Town, Darkness instructs Maleficent to use the Lifeboat again to return to the future. However, unbeknownst to anyone, this sets off a fail safe which begins a countdown to the destruction of both the real and virtual Daybreak Towns.
Back in Virtual Daybreak Town, Lauriam recovers from his battle with Maleficent and overhears the other Union leaders talking about Ventus and Strelitzia. Lauriam confronts them leading to a confrontation with Darkness. Afterwards, Lauriam leads the other Union Leaders to the Lifeboats and Brain begins to work out a plan to escape the data world. He also discovers the fail safe but believes that when the data world is destroyed it should go to sleep, like the real world. Brain uses the remaining Lifeboats to allow himself, Lauriam, Ventus, and Elrena to escape, leaving Ephemer, Skuld and Player behind but promising to figure out a way for them and the other Dandelions to escape. In the real world Brain sends Lauriam, Ventus and Elrena to the future using the Lifeboats, before sending two back to the data world for Ephemer and Skuld. However he is confronted by Luxu, who informs him that the data world was designed as a prison for darkness, and that when it is destroyed it will seal itself rather than go to sleep. Ephemer and Skuld leave the data world using the Lifeboats, before using them in the real world to shelter from the destruction of Daybreak Town. When the real Daybreak Town is destroyed, the virtual one seals itself, causing all the trapped Dandelions to go to sleep, reverting to their heart forms and merging with the Chirithy's to become Dream Eaters. Player elects to forgo the transformation, instead allowing their heart to melt into a new one.
Ansem the Wise creates a data version of Twilight Town to hold Roxas while Sora is having his memories recovered. The virtual Twilight Town is located in a computer within the basement of the old mansion in the real Twilight Town. While Roxas is contained within the data world he has no memory of his life before, as Ansem alters his memories to prevent him from leaving. Eventually Roxas discovers the truth and battles Axel before merging with Sora, who wakes up in the real world. Sora later accesses the virtual Twilight Town in order to travel to The World that Never was using the portal Axel used.
During his travels, Sora learns that the computer at Radiant Garden holds a data world called Space Paranoids. Ansem created the world from data he copied from a computer system at ENCOM and used it for the town's maintenance and his personal research. Sora enters the computer and meets Tron, assisting him with freeing the data world from the control of the MCP and Sark.
After discovering an unknown message in Jiminy's Journal, King Mickey digitizes the contents of the Journal in order to discover the meaning of the message. The King creates a datascape containing worlds from Sora's first adventures, in which a Data-Sora relives Sora's adventures. Maleficent and Pete also gain access to the datascape and try to take it over.
During their Mark of Mastery exam, Sora and Riku enter the Sleeping World of The Grid, a data world created by Kevin Flynn and the world Ansem the Wise copied to create Space Paranoids. While Sora and Riku are taking their exam, Maleficent and Pete infiltrate Disney Castle and take Queen Minnie hostage in order to obtain the datascape created from Jiminy’s Journal, but are thwarted by Lea. After rescuing Sora from Xehanort, Riku inadvertently accesses the data stored in Sora's heart. There he experiences a simulation of Destiny Islands, were he meets Ven, Roxas and Xion, before speaking with a data replica of Ansem the Wise.
Ienzo learns of the Twilight Town datascape and with assistance from Pence, links it to Radiant Garden's computer in order to analyze Ansem's Code. A year after the defeat of Xehanort, everyone is still searching for Sora. Riku speaks with Leon, Yuffie, Aerith and Cid about their work in trying to locate Sora. Cid has been attempting to find information on Sora by searching the data in the Twilight Town and Radiant Garden computer systems. He discovers the real Organization XIII's data in a digital version of the Garden of Assemblage. Hoping to find a clue to the whereabouts of Sora, Riku accesses the data using a digital version of Sora.
The following is a list of known Datascapes and the data worlds they contain:
Daybreak Town Datascape (located within the Clock Tower at Daybreak Town)
Space Paranoids Datascape (located within Ansem the Wise's study at Radiant Garden)
Twilight Town Datascape (located within the Old Mansion at Twilight Town)
Datascape created from Jiminy’s Journal (located within Disney Castle)
The Grid Datascape (location unknown)
Garden of Assemblage Datascape (located within Merlin's house at Radiant Garden)