is a Japanese peer-to-peer

Peer-to-peer

Peer-to-peer computing or networking is a distributed application architecture that partitions tasks or workloads among peers. Peers are equally privileged, equipotent participants in the application...

 file-sharing (P2P) application designed for use with Microsoft Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

 (not to be confused with the video game franchise Perfect Dark

Perfect Dark (series)

Perfect Dark is a science fiction video game franchise created and developed by Rare. The series debuted with the Nintendo 64 video game Perfect Dark in 2000, which received strong acclaim from critics and players, leading to the franchise's expansion. In 2002, Rare was acquired by Microsoft Game...

). It was launched in 2006, its author is known by the pseudonym . Perfect Dark was developed with the intention for it to be the successor to both Winny

Winny

Winny is a Japanese peer-to-peer file-sharing program which claims to be loosely inspired by the design principles behind the Freenet network, which keep user identities untraceable...

 and Share

Share (P2P)

is the name for a closed-source P2P application being developed in Japan by an anonymous author. Since the author of Winny was arrested, Share was developed as its successor, also focusing on higher security...

. As of version 1.02, code-named "STAND ALONE COMPLEX", there is support for the program to run in English, an option that can be selected when the program is installed.
Presently, since Perfect Dark is still being actively developed, the author does not ask that the program's users at this point become dedicated "users" of the software.