Resources  / Checking what is live

How we know a name is live

Once we know which addresses could imitate you, the next question is which of them somebody has actually bought and switched on. That sounds like a simple lookup. It is not, and getting it wrong in either direction is expensive: a false alarm wastes your time, and a missed registration is the one that gets used.

Why asking once gives the wrong answer

• Old answers

  Many of the servers that answer “does this address exist?” remember old answers. A name deleted last month can still look alive.

• Answers that are always yes

  Some servers answer every question with an advertising page of their own. To them, every name exists.

• Failures that look like “no”

  A server that is busy or broken can reply with something that reads exactly like “this name does not exist”.

• Endings that answer for everything

  A few domain endings reply for every possible name, registered or not.

How we get the right one

1. 1 Never trust one answer A change is never decided by one server. When anything looks different, the same question goes to many independent servers at the same moment, and one wrong answer is outvoted.
2. 2 Ask them from different places Servers run by the same network often share a memory, so their agreement proves nothing. We choose servers from different networks.
3. 3 Go to the source when it matters Every domain ending is run by a registry that keeps the official record of which names exist. When the answers disagree, or something seems to have changed, we ask the registry directly.
4. 4 A failure is not an answer An error or a silence counts as “we do not know yet”, never as “not registered”.
5. 5 Hear it twice A name only changes from quiet to live (or back) when the same answer comes back twice in a row, unless the official record has already settled it. One stray answer never becomes an alert.
6. 6 Check the checkers We regularly test the servers we rely on with questions whose answers we already know. A server that gets them wrong is dropped.

Registered is not the same as dangerous

A registered name can sit empty for years, parked with a registrar and doing nothing. We tell those apart from names that have a website or can send mail, because that is the difference between a name that could be used against you one day and one that could be used against you today. The risk score is built on that difference.

Why this works

No single source on the internet can be trusted to tell the truth about every name. Many independent sources that agree, backed by the official record when they do not, can. It is slower than asking once, and it means that when we tell you a name has gone live, it has.