An early and primitive form of messaging systems was developed on private computer networks, like the PLATO system in the early 1970s. Later, UNIX talk messaging systems were used widely by academics and engineers in the 1980s and 1990s. They were used to communicate across the internet.

The first general instant messenger was ICQ. It combined a list, or presence, of contacts with sending messages. In November 1996, ICQ was introduced. It was awarded two patents, from the U.S. patent office.

Now there are many variations of instant messaging. They were developed in many places, each with its own protocol. This resulted in users having many instant messaging applications, simultaneously. This requires several networks to be available. Or, users have a client supporting many protocols, such as Trillian, GAIM or Miranda cients.

There are bulletin board systems (BBS) which are single line. A single caller online and the system operator (sysop) typically chat with each another. As either typed, it appeared real-time for the other person. It was an instant message equivalent.

Many instant messaging services now offer Voice Over IP, web and video conferencing services. Web conferencing services include both video conferencing and instant messaging features.