CPR (Cubase Project) is a special file format developed by Steinberg Media Technologies and originally introduced in 2002 with the release of Cubase SX 1.0.

Cubase Project Files contain no actual audio data. Instead, they contain metadata necessary for properly rendering a project inside Cubase.

This metadata includes (but is not limited to) references to all audio files associated with the given project, information about the total number and type of tracks used in the project, and any automation settings or effects that may have been applied to those tracks, mixer settings, VST settings, and many other global preference settings.

CPR files may also be used for the creation of so-called templates - empty Cubase projects that act as preset environments for specific purposes, such as multi-track recording, surround mixing, stereo mastering etc.

Since CPR files contain no actual audio data, it's important to know that in order to open a CPR file properly on another machine, all external audio and VST files should also be transferred to that machine. Also, in order to convert CPR files to MP3 for playback on other devices, you need to open up the file in Cubase and use the File > Export > Audio Mixdown menu.