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Intermediate

What is DNS

Full name: Domain Name System

Also known as: domain name system, DNS records, nameservers

Definition

DNS (Domain Name System) is the internet's phonebook: it turns a name like example.co.il into an IP address, and its records set where your site and email go.

Why it matters

One wrong DNS row can take down your site or your email, and changes do not show everywhere at once.

Common mistakes

Deleting or overwriting the MX records during a website move, which stops the email.

Related terms

Worked exampleIllustration

The DNS panel of example.co.il

Records

  • The bare name to the site at 192.0.2.10A
  • www as an alias of host.example.netCNAME
  • Email to smtp.google.com, priority 1MX
  • SPF: v=spf1 include:_spf.google.com ~allTXT
  • DMARC at _dmarc, a policy that tells receivers what to do with mail that fails SPF and DKIM, and where to send reportsTXT

TTL

How long resolvers may keep each answer, set per record.

Steps

  1. A day ahead, because the old TTL is one day, the owner lowers the TTL of the A record.

  2. On the day, the owner changes the A record to the new host's address.

  3. The owner checks the new answer with a public DNS lookup tool.

  4. Once the site answers from the new host, the owner raises the TTL again.

Lower the TTL at least one old TTL period before a move, and the switch takes minutes instead of a day.

Illustration

How it works

DNSThe browser asksexample.co.il?⁨The DNS phonebook⁩site-a.com203.0.113.7example.co.il192.0.2.10site-b.com198.51.100.4192.0.2.10the right server

The browser knows the name example.co.il, DNS finds its address 192.0.2.10, and the browser goes to that server.

DNS turns the name a person types into the numeric address computers use, so the browser reaches the right server.

Name, directory, building, mailbox

The directory holds one row per job: this one sends the site to its server, that one sends the email to the mail service.The name (domain)example.co.ilThe directory (DNS)Website192.0.2.10Emailsmtp.google.comThe building(hosting)The site opensThe mailbox(email)Email arrives

The directory holds one row per job: this one sends the site to its server, that one sends the email to the mail service.

The domain is the name, DNS the directory that says where the name leads, hosting the building the site lives in, and email a mailbox that can live somewhere else.

Definition

DNS is a hierarchical, distributed naming system that translates domain names into the IP addresses computers use, and holds other records about each domain. The owner sets these records in a DNS panel, usually at the registrar, the host or a separate DNS provider. The six an owner meets: A points a name to an IPv4 address, AAAA to an IPv6 address, CNAME makes one name an alias of another (typical for www), MX says where the domain's email goes, TXT holds text used for SPF, DKIM, DMARC and ownership checks by services such as Google and Meta, and NS names the company that answers for the domain. Each record carries a TTL (time to live), a valid until stamp that tells resolvers how long they may keep a cached answer.

Why it matters

Nothing travels after a change: DNS works on a pull model, and each resolver keeps the old answer until the TTL of the record it cached runs out, which is why a change can take from minutes up to the often quoted worst case of 48 hours. Since 1 February 2024 Gmail requires everyone who sends to Gmail accounts to meet its sender rules, including SPF or DKIM, and senders of more than 5,000 messages a day must also publish DMARC (a record that tells receivers what to do with mail that fails those checks) and offer one click unsubscribe. DNS hijacking usually starts with a stolen registrar or DNS account, so two step login and the registrar lock protect DNS too.

Directly related: Domain, Hosting, Server.

Improvement tips

  • Before any change, find out who holds your DNS by checking where the nameservers point.
  • Copy every existing record before an edit or a move, so a missing MX or TXT row can be restored in minutes.
  • Lower the TTL at least one old TTL period before a planned change, and raise it again afterwards.
  • Publish SPF, DKIM and DMARC for the domain you send email from, so Gmail and other providers accept your mail.

Common mistakes

  • Changing records without a copy of the old values, so nobody can undo the change.
  • Lowering the TTL only an hour before a move, while resolvers still hold the old answer for the old TTL.
  • Leaving the DNS account with a single password and no two step login.

Related terms

TechnologyBeginner

Domain

A domain is your unique name on the internet, like example.co.il, rented for a set period through a registrar. Through DNS it points to your site and email.

TechnologyBeginner

Hosting

Hosting is a service that rents you space on a server connected to the internet all the time, so your website is available to every visitor.

TechnologyBeginner

Server

A server is a computer, or a program on one, that receives requests from other programs, such as a visitor's browser, processes them and sends back an answer.

Quick check

Why can a DNS change take hours to show everywhere?

Choose an answer

Frequently asked questions

Do I need to understand DNS before I start my business?
You need to know that DNS is a short list of records that decides where your site and email go, and who can edit it. The first time you connect a domain to a website builder or to business email, you will add records there.
When does DNS first become relevant for a new business?
When you connect your domain to email or to a website. The email provider gives you MX and TXT records, the host gives you an A or CNAME record, and you enter them in the DNS panel.
How long do DNS changes take to work?
From minutes to many hours. Nothing is pushed out: each resolver keeps the old answer until the record's TTL runs out. The 48 hours people quote is a worst case from long TTLs and caching, not a fixed delay.
Should my registrar, my host or a separate provider manage my DNS?
Any of them can. What matters is that you know which one it is, that the account is in the business's name with two step login, and that you keep a copy of the records. The nameservers show which company answers for your domain.
Why does DNS matter for a business already running?
Your site, your email and the ownership checks of services like Google and Meta all depend on DNS records. One wrong edit can stop the email or send visitors to the wrong place.
What goes wrong when someone deletes DNS records?
Deleting MX records stops the domain's email. Deleting TXT records can break SPF, DKIM or a service's ownership check, so mail lands in spam or an integration stops. Keep a copy of all records before any edit.
How do I change DNS without breaking my site?
Lower the TTL at least one old TTL period ahead: if the old TTL is 24 hours, a day is the minimum. Make the change, check it with a public DNS lookup tool, then raise the TTL again.
How does DNS keep my business email out of spam?
Three TXT records prove your mail is genuine: SPF lists the servers allowed to send, DKIM publishes the key that checks each message's signature, and DMARC tells receivers what to do when those checks fail. Since February 2024 Gmail requires SPF or DKIM from all senders, and DMARC from senders of more than 5,000 messages a day.
What does DNS actually mean in plain words?
The internet's phonebook. You type a name, DNS looks up the number the computers need, and every entry carries a valid until stamp that says how long the answer may be reused.
Is changing DNS records risky?
A typo can stop your site or email, so the risk is real but manageable: copy the old records, change one thing at a time and check the result. Many providers offer ready templates for common services.
Do I need a developer to manage DNS?
Not for common setups such as connecting business email or a website builder, which come with step by step instructions. For a move between hosts or a complex setup, a developer or the host's support should do it.
What is an IP address in relation to DNS?
An IP address is the number that identifies a server on the internet, such as 192.0.2.10 in documentation examples. DNS lets people use a name instead, and the A record is the entry that links the two.

Sources: IETF RFC 1034, Domain Names, Concepts and Facilities, 1987, IETF RFC 5737, IPv4 Address Blocks Reserved for Documentation, 2010, Google, Email sender guidelines (support.google.com/mail/answer/81126), read 23 September 2026, Google Workspace Admin Help, Set up MX records for Google Workspace, and Set up SPF (knowledge.workspace.google.com), read 23 September 2026, Cloudflare Developers, DNS documentation on TTL and caching (developers.cloudflare.com), read 23 September 2026

Last reviewed: 2026-09-23

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