[memset]

Have built a domain registrar.

The industry term for this business is called “drop catching” https://en.m.wikipedia.org/wiki/Domain_drop_catching

Domain registries provide registrars with reports of domains which are set to expire, and if you’re not a registrar yourself, you can often purchase these lists on a secondary market or use APIs built upon serving this information.

But even if you don’t have that list, you can do a Whois search for any domain and know its expiration. You could build your own database!

Note that most domains have a grace period (eg, 30 days) where the original owner can renew even after it has expired. So it’s not like you’d be able to steal someone’s domain just because of a clerical error.

[iso947]

> Note that most domains have a grace period (eg, 30 days) where the original owner can renew even after it has expired.

Back in the day Microsoft dropped the ball with passport.com, shutting down hotmail over Christmas.

https://m.slashdot.org/story/8999

https://www.doublewide.net/faq.html

You’d think Microsoft would have learnt their lesson but no, 3 years later it was Hotmail.co.uk that dropped off

https://www.theregister.com/2003/11/06/microsoft_forgets_to_...

[memset]

It turns out that grace periods (called a "redemption grace period") weren't proposed until 2003. I'm not actually sure when this process was approved by ICANN - sometime between 2003 and 2013.

The latest version of ICANN's registrar accreditation agreement, in 2013, includes grace period provisions. https://www.icann.org/resources/pages/approved-with-specs-20...