ICQ allows the sending of text messages, URLs, multi-user chats, file transfers, greeting cards and more.

ICQ users are identified by numbers called UIN, distributed in sequential order (though it is rumored there are gaps in the sequence). New users are now given a UIN of well over 100,000,000, and low numbers (six digits or less) have been auctioned on eBay by users who signed up in ICQ's early days.

AOL acquired Mirabilis and ICQ in 1998. AOL's OSCAR network protocol used by ICQ is proprietary, but a number of people have created more or less compatible third-party clients, including:

• centericq - supports ICQ, Yahoo!, AIM, MSN, IRC and Jabber
• Fire - supports ICQ, Yahoo!, AIM, MSN, IRC, and Jabber
• Gaim - supports ICQ, Yahoo!, AIM, MSN, IRC, Jabber and Gadu-Gadu
• GnomeICU (previously GtkICQ)
• Licq
• mICQ
• Miranda IM - plugin based, supports ICQ, Yahoo!, AIM, MSN, IRC, Jabber, Gadu-Gadu, BNet, and others
• Trillian - supports ICQ, Yahoo!, AIM, MSN, IRC, Jabber and others
• YSM

The Instant Messaging community wishes to remove the proprietary protocol of IMs like ICQ and create a single instant messaging format, called Unified Instant Messaging under the IPv6 Protocol, involving AOL, Microsoft, and Yahoo.

AOL has recently begun making its ICQ software more AIM-like by adding AIM Smilies, as well as introducing cross AIM/ICQ communication. Users on ICQ are able to communicate with AIM users, however such capability is in beta stages.

External Links

• The Official ICQ Website
• Press release announcing the acquisition of ICQ by AOL
• ICQ protocol database
• Unified Instant Messaging over IPv6: A brief introduction on Instant Messaging and its products, followed by a description of some Peer-to-Peer systems and platforms. Then the IETF standards on Instant Messaging are presented. Finally, a framework for Agent-based Unified Instant Messaging over IPv6 is proposed.