ICQ is one of the first popular instant messaging clients for computers. It was first developed by a group of Israeli developers who saw a lack for a medium to locate and connect different computer users in real time through the internet. The company and program were acquired by AOL (Then a subsidiary of Time Warner) in 1998 and made the protocol compliant with AOL Instant Messenger.

ICQ Version 3.02 is compatible with Mac OS 8.1-8.5 and 3.2 Beta 5 is compatible with OS 8.6. Version 3.4.23 is compatible with OS 9-X.