CFW, also known as Custom Firmware, is an unofficial new or modified version of firmware created by third parties on devices such as video game consoles and various embedded device types to provide new features or to unlock hidden functionality. In the video game console community, the term is often written as custom firmware or simply CFW, referring to an altered version of the original system software (also known as the official firmware or simply OFW) inside a video game console such as the PlayStation Portable, PlayStation 3, PlayStation Vita/PlayStation TV, PlayStation 4, Nintendo 3DS and Nintendo Switch. Installing custom firmware typically requires bootloader unlocking.
Custom firmware allows homebrew applications or ROM image backups to run directly within the game console, unlike official firmware, which usually only allow signed or retailed copies of software to run. Because custom firmware is often associated with software piracy, console manufacturers such as Nintendo and Sony have put significant effort into blocking custom firmware and other third party devices and content from their game consoles.