upward compatibility; forward compatibility
Technical term for compatibility with higher-tier or newer systems. Often contrasted with 上位互換性 (backward compatibility).
This software has forward compatibility, so files created in the new version can be opened in the old version.
downward compatibility; backward compatibility
Often used incorrectly to mean backward compatibility. The correct term for backward compatibility is 上位互換性. This sense is marked as incorrect usage.
See also: 上位互換性
Using 下位互換性 to mean compatibility with older devices is often considered a misuse.