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, can be used to create replicas of Organisation XIII from their data 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 an unknown world 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.
At some point, Maleficent from the future manages to travel back in time to the Enchanted Dominion and attempts to change her fate, but is thwarted. Afterwards, she discovers from an unknown figure 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. Later, she learns from the unknown figure 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.
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 Kingdom Hearts I and Chain of Memories, in which a data version of Sora relives the adventures of the real Sora. 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 Journal datascape, 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 analyse the data. 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 Organisation 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:
Book of Prophecies 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)
Jiminy's Journal Datascape (located within Disney Castle)
Garden of Assemblage Datascape (located within Merlin's house at Radiant Garden)