It is also a terminal emulator, serial console, and network file transfer software free and open source. PuTTY is open-source software available with source code and is developed and supported by a group of volunteers. PuTTY is primarily written and maintained by Simon Tatham, a British programmer for the Windows platform. PuTTY There is no official definition of “PuTTY.” Still, the term is commonly used as an application for both SSH and telnet and includes an xterm terminal emulator, and PuTTY is an alternative to telnet clients.