How relaible is WHOIS data from long ago?

[EbookLover]

Is whois info pretty reliable or is it kind of spotty before a certain year, say 2005 or 1999 or whatever?

Specifically what I'm trying to figure out is, if whois.sc/Domaintools shows that a .com domain was never registered before, can I take that as gospel? Or is it possible it was actually registered for a small period of time before a certain year but whois data might not have such info since it was before a certain date.

 

[Kate]

Typically they rely on zone files. So it is just a matter of comparing today's release against the previous day, spot additions & deletions, and then they try to scrape the whois record. But whois is not needed to determine if the domain name has been registered.
However the zone files do not contain all domains, like those with no name servers., domains on hold etc.

And of course the domain name may have been registered (and dropped) before they started tracking domains.
Have a look at archive.org just in case.

I think that only the registry (Verisign) could guarantee the name has not been registered before, provided that they carry the whole registration history of the TLD, that is before they were appointed as caretaker.
I am not sure we have all the records from SRI from the early days (I mean around 1986), if they even kept and archived everything properly.

 

[EbookLover]

Thanks for the explanation.

Also, archive.org isn't reliable, though, and one reason is that, until 2017, a webmaster was able to block archive.org on his site(s) via robot.txt file.