Every TLD registry maintains data about registered domain names. They publish this data over the WHOIS protocol. Currently, 36 registries publish the location of their WHOIS servers using SRV records.Finding the correct WHOIS server for a domain name isn't trivial. By NsLookup.io. Licensed under CC By 4.0.
For example, the .de TLD registry publishes the location of its WHOIS server in an SRV record:
I've queried the SRV records for every TLD according to ICANN's TLD list on 2023-05-15. This show that out of the 1479 TLDs, only 36 have adopted this practice. That's less than 2.5%.
After 50 years of WHOIS, it is — ironically — still hard to know who the authoritative WHOIS server is.
This is the full list of TLDs that publish the location of their WHOIS servers using SRV records as of 2023-05-15:
