Uh-oh! It’s 20 years to the day since the introduction of one of the internet’s most well-remembered chat apps: ICQ .

It was pretty barebones in its first form, released by its Israeli student creators in November 1996, but over the next year had versions available for Windows 95, 3.1 (not everyone wanted to upgrade) and Macs (presumably System 7).

Remember this noise?

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The online chat world was a simpler one at the time, at least in terms of the market and technology used. ICQ was simple and unencrypted, and every user was assigned a number — six digits at first, more later — for ease of operation.

You could message anyone whose number you had, and you could gather them by fair means or foul, on IRC, BBS or AOL — or at school, of course, the way you’d exchange phone numbers. At first, contact lists and other info were even kept client-side, making it an early success of peer-to-peer as well as messaging. And a relatively open architecture meant it could be cloned and forked.

Who can forget the little status icons, the sense of discovery and independence, the possibilities of a platform like this? It was popular among nerds of the day (source: was one), but this type of chat app quickly outgrew its humble beginnings.

AOL Instant Messenger got its standalone in mid-1997, building on the concept and making it an easy transition from millions of AOL subscribers. Along with MSN Messenger, that pretty much blew the lid off the chat market, and prefigured today’s fractured ecosystem. (Disclosure: AOL owns TechCrunch — it was rather a different company back then, though.)

Mirabilis, the company formed around ICQ and its technologies, was bought shortly thereafter by AOL for $407 million ($287M down and $120M more contingent on performance) — an eye-popping number at the time, though we’ve gotten used to such things in the two decades since. In 2001, it had more than 100 million users.

I’m the wrong person to go into all the changes since then — the many forward-thinking features added, the sale in 2008 to what would later become the Mail.ru group, its enduring popularity in Russia and so on. You’d be better off reading this Medium post.

It’s still available, and although it’s hard to say why you should choose it over the many other offerings today, it’s sort of comforting to think that the brand and basic function of something like ICQ can endure for so long in so chaotic an environment. Oh, and the desktop version is open source.

Happy 20th, ICQ! Many happy returns.