Save compatibility allows worlds from older versions of Dwarf Fortress to be played on newer versions of Dwarf Fortress. Generally, Dwarf Fortress versions are backwards-compatible, which means that older saves can be imported into newer versions without problems. However, many new features and some bug fixes do not apply to older saves. This occurs because the changes affect world generation or the raw files.
Generally, Dwarf Fortress versions are not forwards-compatible, which means that newer saves cannot be imported into older versions, with a few exceptions for very minor releases. This is rarely necessary, however; if a newer version introduces a bug that makes the game unplayable, a hotfix for the newer version is usually released shortly after.
Sometimes, a release "breaks save compatibility". This means that all older saves do not work with the release. Save compatibility is usually broken when major changes are made, such as when the major component of the version number is increased. Sometimes, due to save file corruption bugs, save compatibility is broken despite the change made being minor.
Recent save compatibility breakages include:
- Version 0.40.03 broke save compatibility with all previous 0.40 versions because of a save file corruption caused by historical births being assigned to player fortresses and a problem with large city walls.
- Version 0.40.02 broke save compatibility with 0.40.01 because of a save file corruption caused by a malfunctioning autosave feature.
- Version 0.40.01, because it was a major release, broke save compatibility with version 0.34.11 and all previous versions.
- Version 0.34.02 broke save compatibility due to a major save corruption bug caused by malfunctioning buildings.
- Version 0.34.01, as with most major releases, broke save compatibility with version 0.31.25 and older.
- Version 0.31.01, being a major release, broke save compatibility with version 0.28.181.40d and previous versions.
- Version 0.27.169.32a was the first major release that broke save compatibility with older saves (from version 0.23 and older).