---
title: "DNS"
description: "DNS is the distributed system that translates domain names into IP addresses. Learn how resolution works, common record types, caching and TTL."
url: "https://nodea.io/en/glossary/dns"
lang: "en"
updated: "2026-07-13"
---

# DNS

> DNS (Domain Name System) is the distributed, hierarchical naming system that translates human-friendly domain names such as example.com into the IP addresses machines use.

**DNS** (*Domain Name System*) is the distributed, hierarchical naming system that translates human-readable domain names — like *example.com* — into the IP addresses computers actually connect to. Often called the internet's phone book, it is critical infrastructure in the most literal sense: when DNS fails, websites and email become unreachable even though the servers behind them are perfectly healthy.

## How DNS resolution works

When you type an address into a browser, a resolver (your ISP's or a public one such as 1.1.1.1 or 8.8.8.8) performs a recursive lookup:

1. it asks a **root server** which servers handle the *.com* zone,
2. the TLD server replies with the domain's **authoritative name servers** (its NS records),
3. an authoritative server returns the requested record — for example an [A record](https://nodea.io/en/glossary/a-record) containing the IPv4 address,
4. the answer goes back to the browser and is cached by the resolver for the duration set in the record's [TTL](https://nodea.io/en/glossary/ttl).

Thanks to caching, the vast majority of lookups never leave the resolver and complete in milliseconds — which is also why zone changes propagate gradually rather than instantly.

### Essential record types

- **A / AAAA** — IPv4 / IPv6 address of a host,
- **CNAME** — an alias pointing at another name,
- **MX** — mail servers accepting email for the domain (see [MX record](https://nodea.io/en/glossary/mx-record)),
- **TXT** — free-form text used for SPF, DKIM, DMARC and ownership verification,
- **NS and SOA** — zone delegation and zone parameters.

## DNS in practice

You touch DNS at every infrastructure change: pointing a domain at a hosting account, moving a site to a new server (updating A records), configuring email (MX plus authentication records), or fronting a site with a CDN. Records are edited in the control panel of your DNS provider or domain registrar. Operational best practices include lowering TTLs ahead of planned changes, running at least two name servers in separate locations for redundancy, and verifying records after any migration with *dig* or *nslookup*. For tamper-proof responses, zones can additionally be signed with DNSSEC.

### Why do DNS changes take time to apply?

Because resolvers cache answers for the record's TTL. Until the cached copy expires, they keep returning the old value, so a change spreads gradually across the internet. Lowering the TTL a day before a planned migration makes the switch nearly instant.

## Related

- [A record](https://nodea.io/en/glossary/a-record)
- [MX record](https://nodea.io/en/glossary/mx-record)
- [DNS Server](https://nodea.io/en/glossary/dns-server)
- [DNS propagation](https://nodea.io/en/glossary/dns-propagation)
- [TTL](https://nodea.io/en/glossary/ttl)

---

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