Sony regularly released firmware updates for its PlayStation Portable system, and encouraged PSP owners to upgrade the PSP system software. To increase system software upgrades, Sony encoded their games so that some of them require newer versions of the system software. This is a list of PSP games having such requirements. All system software updates are backwards-compatible; that is, all games that work on system software version 1.5 will work on version 2.0, and so on.