Mirabilis enjoyed first-mover advantage, attracting millions of early Internet users enticed by the proposition of chatting with friends and family in real-time.

This number (I somehow still remember mine by heart some 20 years later), along with custom handles and an attached email address, were used to search for other users on the platform. Users were issued a unique User Identification Number, or UIN, upon registration. ICQ offered a number of innovative features including multi-user chat, async offline messaging, resumable file transfers and a searchable directory. Incredibly enough, ICQ has also outlasted its chief competitors: AIM shut down at the end of 2017, Yahoo's communications program bit the bullet in mid-2018 and Microsoft laid its Messenger client to rest in 2014.

Launched after less than two months of development from Israeli company Mirabilis, it predated and influenced many of the popular chat programs of the era including AOL Instant Messenger, Yahoo! Messenger and MSN Messenger.

Microsoft's trailblazing Windows 95 was barely a year old, Nintendo had just introduced the N64, and those with a reason to have a cell phone actually used it to talk on. ICQ, short for the phrase 'I Seek You,' laid the groundwork for standalone instant messaging clients when it arrived in November 1996.

What is icq number