What Is DNS?
Understand DNS records, resolvers, and how DNS lookups work.
DNS (Domain Name System) is the internet's naming infrastructure. It translates human-readable domain names like example.com into the numeric IP addresses that computers use to locate each other on the network. Without DNS, users would need to remember IP addresses instead of domain names for every website and service they use.
How DNS resolution works
When you type a domain name into a browser, a multi-step lookup process begins. Your device first checks its local DNS cache. If the answer is not cached, the query goes to a recursive resolver (typically operated by your ISP or a public DNS service like Google or Cloudflare). The resolver then queries the DNS hierarchy: root servers, then top-level domain (TLD) servers, then the authoritative nameserver for the domain, which returns the final answer.
Common DNS record types
- A record -- maps a hostname to an IPv4 address
- AAAA record -- maps a hostname to an IPv6 address
- MX record -- specifies mail servers for a domain
- TXT record -- stores text data for verification, SPF, DMARC, and other policies
- NS record -- identifies the authoritative nameservers for a domain
- CNAME record -- creates an alias that points one hostname to another
- SOA record -- contains zone metadata including the primary nameserver and timing values
- CAA record -- specifies which certificate authorities may issue certificates
DNS caching and TTL
DNS answers include a TTL (Time To Live) value that tells resolvers how long to cache the response. This reduces query load and improves performance, but it also means that DNS changes do not take effect instantly. Propagation delays depend on the TTL values of the old records and resolver caching behavior.
Why DNS matters for troubleshooting
DNS problems are among the most common causes of website and email issues. Misconfigured records can prevent websites from loading, emails from being delivered, or certificates from being issued. DNS lookup tools help administrators verify that records are correct, that changes have propagated, and that no conflicting or stale records exist.