The early chat programs only worked on one computer. Some of the early programs written for timesharing computers in the 1960's were designed to support real-time chat. Several programs were written by people in different universities and research organizations around the United States. Since there was no network, these chat programs could only be used by those connected to the same computer. The computer terminals could be distributed throughout a building, or in different buildings at a close proximity.

EMISARI (Emergency Management Information Systems And Reference Index) was the first multi-machine chat system developed in 1971 by Murray Turoff for the US Office of Emergency Preparedness (OEP). The original purpose of the system was to help exchange information on opinion surveys between people in different locations. The first practical application was in coordinating information for President Nixon's wage and price control program to fight high inflation. Users of EMISARI accessed the system through teletypewriter terminals linked to a central computer through long distance phone lines. The EMISARI chat functionality was called the Party Line and was originally developed to replace telephone conferences which might have 30 participants, but where no-one could effectively respond and take part in a meaningful discussion. Party Line had features like a list of current participants, and an alert when someone joined or left the group. Based on his EMISARI experience, in 1975 Murray Turoff, then at the New Jersey Institute of Technology, developed one of the first conferencing systems. PLANET, developed in 1973by Jacques Vallee from the Institute of the Future was the first ARPANET chat system and enabled anybody on the network to log into the system. It was used in a series of evaluation studies, but was not distributed to the wider ARPANET community.

Talk was a basic but powerful early chat system supported by many Unix computers on the ARPANET in the 1970's. Participants in a talk conversation had to be logged in directly or over the network to the same computer, which would then provide conferencing capabilities between users. A user could ask the talk system for a list of people currently on the system, and then send a message to any of those users which would pop up on the user's terminal.

Talkers are usually stand-alone, proprietary systems that have many of the same features of IRC, and were developed at almost the same time. However, IRC is an open Internet protocol that generally runs networks of servers supporting thousands of users at once.

Internet Relay Chat IRC gave birth to the Internet chat movement and is the most widely used Internet chat system today. Invented by a graduate student named Jarkko Oikarinen at the University of Oulu, Finland in 1988 it was a much improved version of the Talk program then available on most Unix computers. Partly inspired by Jyrki Kuoppala's "rmsg" program, and partly by Bitnet Relay Chat, Oikarinen decided to improve the existing multi-user chat program on OuluBox, called MultiUser Talk (MUT), written by Jukka Pihl.

When IRC started regularly hosting users, Oikarinen asked some friends at Tampere University of Technology and Helsinki University of Technology to start running IRC servers to distribute the load. Other universities joined soon after. Markku Jrvinen made the client program more user-friendly by including support for Emacs editor commands, and before long IRC was in use across Finland on the Finnish network FUNET, and then on the Scandinavian network NORDUNET.

Oikarinen got an account on the well-known machine "ai.ai.mit.edu" at MIT, from which he recruited the first IRC user outside Scandinavia, Mike Jacobs, and also gave the IRC software to Vijay Subramaniam who passed the software to his friends Jeff Trim at the University of Denver, and David Bleckmann and Todd Ferguson at Oregon State University, who began running IRC on their machines "orion.cair.du.edu" and "jacobcs.cs.orst.edu". They emailed Jarkko and obtained connections to the Finnish IRC network, and the number of IRC servers began to grow rapidly across both North American and Europe.