Whois

The public record of a domain’s registration: registrar, dates and, where not redacted, the owner.

Use it to check registration dates and expiry before acquiring a domain or evaluating a link source.

Privacy services hide ownership on most domains now, so absence of data proves nothing either way.

It is the quickest way to see whether a site is what it claims to be, or one of twenty registered the same week.

A domain quietly approaching expiry is a risk worth catching before it lapses.