DNS, the Domain Name System, helps software find information associated with a domain name. When you open a website, your device typically asks a recursive resolver for a record; the resolver may use a cached answer or follow the DNS hierarchy to a server authoritative for the requested zone. It then returns the answer—or an error—to your device.
What DNS is—and what it is not
DNS is a distributed naming system organized as a hierarchy. It stores different kinds of information in resource records associated with names. It is not one central server, nor is it simply a permanent directory that translates every website name into one IP address.
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A DNS query identifies both a name and the type of information requested. Some queries support website connections; others support services such as email. The DNS standards describe the namespace and records, name servers, and resolvers as major components of the system. IETF RFC 1034 sets out the concepts, while IETF RFC 1035 specifies implementation details.
How a DNS lookup works
Consider a simplified example: a user enters www.example.com. The exact route can vary depending on cached data, aliases, delegation, the record type, and errors; not every lookup makes the same number of network requests.
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- The device asks a recursive resolver. A stub resolver on the device sends a request to the recursive resolver configured for it, often through the network or service settings.
- The resolver checks its cache. If it has a suitable unexpired answer, it can return it without repeating the upstream lookup.
- If needed, the resolver follows referrals. A root server directs it toward the relevant top-level domain (TLD); a TLD server can direct it toward the authoritative name servers for the domain.
- An authoritative server supplies zone data. The server responsible for the relevant zone returns the requested record or information about an alias. The resolver may need to follow that alias to find the final data.
- The resolver replies to the device. It returns the answer or an error and may cache the data for later queries.
Root and TLD servers generally guide resolvers through referrals; they usually do not provide the final record for a website name. The recursive resolver does lookup work on the client’s behalf, while the authoritative server serves records for the zones it is responsible for. Cloudflare’s DNS overview explains these roles, and ICANN’s overview of DNS root service operations describes how root servers direct resolvers toward TLD servers.
Recursive resolver vs. authoritative name server
| Role | What it does | Data it uses | Typical place in a lookup |
|---|---|---|---|
| Recursive resolver | Finds an answer or returns an error on behalf of the client. | May use cached data and gather information from other DNS servers. | Receives the client’s request and handles the lookup. |
| Authoritative name server | Provides DNS data for the zone it serves. | Authoritative records for its zone. | Supplies requested zone data when the resolver reaches the relevant authority. |
What DNS records contain
Different record types answer different questions. For example:
- A and AAAA: provide IPv4 and IPv6 address records, respectively.
- MX: provides information used to route email for a domain.
- CNAME: identifies an alias for another name.
These examples are not an exhaustive list. A query for a domain does not necessarily ask for an address, and an alias or delegation can lead to additional names and lookups.
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Why DNS caching matters
Resolvers cache DNS data for a configured lifetime. Reusing a valid cached answer can make later lookups faster and reduce the need to repeat the upstream path. Once that lifetime expires, a resolver may need to obtain fresh data.
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This is why a DNS change may not appear to everyone at the same moment. The time depends on record lifetimes and resolver behavior, so there is no universal propagation time. A resolver with an older cached answer may continue using it until its cache entry expires.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What DNSSEC protects—and what it does not
Ordinary DNS does not by itself provide strong authentication of responses. DNSSEC adds data-origin authentication and integrity protection: a validating resolver checks signatures on DNS data and follows a chain of trust through signed delegations to a configured trust anchor. ICANN explains the distinction in its DNSSEC overview.
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DNSSEC does not encrypt DNS queries or responses, conceal which domain a user visits, or prevent every DNS-related threat. Its purpose is to help a validating resolver check that DNS data is authentic and has not been altered.
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