DNS (Domain Name System) is the internet's phone book: it converts readable names such as example.com into IP addresses that computers use to connect.
How a query happens
- The browser asks the resolver configured in your system.
- Without a cached answer, the resolver queries the root servers, then the TLD server and finally the domain's authoritative server.
- The answer is returned and cached for the TTL defined on the record.
Main record types
- A: the domain's IPv4 address.
- AAAA: the IPv6 address.
- CNAME: an alias pointing to another name.
- MX: mail servers.
- TXT: verification strings and policies such as SPF and DMARC.
- NS: the domain's authoritative servers.
When something goes wrong
If one site fails while others work, DNS may be the cause. Use the DNS Checker to see the resolver's real answer and status (NOERROR or NXDOMAIN). Stale cache and high TTLs commonly explain changes that seem to have no effect.