PuTTY

PuTTY is a free and open-source terminal emulator, serial console, and network file transfer application. It provides several programs for secure remote connections, most notably an SSH client, along with support for Telnet, rlogin, SCP, and raw socket connections. The main PuTTY executable offers a graphical terminal interface, while a family of companion utilities supplies additional capabilities for file transfer, key management, and automated connections.

PuTTY was created by Simon Tatham for Windows, with the initial release in 1999. It was designed to be lightweight, portable, and easy to deploy for remote administration of Unix-like systems. The project uses a permissive BSD-like license and is maintained by volunteers and contributors; while optimized for Windows, several ports exist for other operating systems and environments.

Key components include PuTTY (the terminal emulator), PuTTYgen (SSH key generation), Pageant (SSH authentication agent), PSCP and PSFTP (secure file copy programs), and Plink (command-line connection tool). PuTTY supports SSH1 and SSH2, session encryption, host key verification, and features such as SSH tunneling (port forwarding) and X11 forwarding when an X server is available. It also provides a variety of configuration options for keyboard handling, terminal modes, and proxy settings.

PuTTY is widely used on Windows for remote administration of servers, network devices, and other equipment. Its long history and simplicity have made it a technology baseline for secure remote access, and it remains a common alternative to more modern clients and to Windows' built-in SSH support.