Telnet is a system for text-based command line interface connections between computers. Both a local network and the Internet can be used to establish a telnet link.

A Telnet link needs a Telnet server operating on the distant computer, as well as a client program on the local computer where instructions are entered (where the commands are carried out). After establishing a connection, the command line on the client will function similarly to the server, taking commands and producing results.

In order to allow computer users at colleges and research organizations to access their room-sized mainframe computers from smaller, more opportunely placed computer interfaces, the Telnet protocol was created in 1969. It does not secure its data because it was created for use on a private network, prior to the creation of the Internet. Telnet is no longer commonly used because data, including user names and passwords, is sent as clear text and is readily readable if captured by a third party. Now, alternative methods like SSH are utilized.