How to determine if a domain is purchased or not?

Question

Domain name market

Hi all.
Tell me how to determine if a domain is purchased or not?
I found this option by checking dns records. If not, then the domain is most likely free. Here is a function that implements this in php (checkdnsrr).
But as you understand, dns may not be specified. Are there any options?

Answer 1

whois. domains are checked through whois, not dns.

Answer 2

There is an option to use the tool that is intended for this. If the domain is parked , for example, then there will be no records in the DNS, but it is not free :)