Upon selecting and loading a singleplayer world, the game will check if the client has a data version newer or older than the selected world. If it does, the game will then prompt the user whether they want to back up their world before playing it if the world is older, or warn them that their world map become corrupted if the world is newer.
Every version of Java Edition since 15w32a, including minor releases and snapshots, has its own data version. The version takes the form of an ever-increasing positive integer, unlike client versions which have different parts of the version separated by periods (.). Data versions are necessary because client versions usually cannot be directly compared since they use different formats (i.e., "1.14" and "19w02a" cannot be compared). Data versions may skip numbers between major releases.
The data version is stored in two places inside the level.dat file of a world save: in the root
Data compound named
DataVersion and also in the
Version compound named
- Data: Information about the level.dat file.
- DataVersion: An integer displaying the data version.
- Version: Versioning information about when the world was last saved.
- Id: An integer displaying the data version.
The latest release version, 1.15.2, has a data version of 2230. The latest development version, 20w15a, has a data version of 2525.