GLOSSARY · DOMAIN NAME SYSTEM
DNS
DNS is the internet's naming system. It converts names people can remember, such as example.com, into the IP addresses computers use to reach each other. It works like a distributed phone book, held by many servers, where each record answers a particular kind of question.
Why it matters
Almost every connection begins with a DNS lookup, which makes DNS a rich record of what you do online. Traditional DNS is not encrypted, so the network between you and the resolver can read the names you ask for. Wrong or poisoned DNS answers can send you to the wrong server, which is why encrypted DNS and careful resolver choice matter.
In practice
DNS holds more than addresses. Records include A and AAAA for addresses, MX for email, TXT for verification and policy, NS for name servers and PTR for reverse lookups. Changes spread as caches expire, controlled by a time-to-live value. You can inspect any of these records with the DNS lookup tool.
Related terms
- DNS resolver: A DNS resolver is the server that does the lookup work on your behalf.
- DoH: DNS over HTTPS wraps DNS questions and answers inside ordinary encrypted HTTPS traffic to a resolver, as described in RFC 8484.
- DoT: DNS over TLS encrypts DNS traffic between your device and a resolver using the same TLS security that protects websites, as set out in RFC 7858.
- Reverse DNS: Reverse DNS turns an IP address back into a name, the opposite of a normal lookup.