Basics Level 1

How DNS and Domains Work

How typing a URL turns into connecting to a server. Domain names, DNS records, nameservers, and why changes take time to propagate.

5 min read No prior knowledge needed

Quick Answer

When you type example.com in your browser, DNS (Domain Name System) translates that human-readable name into an IP address like 93.184.216.34 that computers use to find each other. It’s the internet’s phone book—you look up a name, you get an address.

The problem DNS solves

Computers find each other using IP addresses: 93.184.216.34 or 2606:2800:220:1:248:1893:25c8:1946.

Humans can’t remember those. We remember names: google.com, github.com, yourapp.com.

DNS bridges this gap. When you visit a website:

You type: example.com
DNS returns: 93.184.216.34
Browser connects to: 93.184.216.34

How a DNS lookup works

When you type www.example.com and hit enter:

1. Browser checks its cache
   ↓ (not found)
2. OS checks its cache
   ↓ (not found)
3. Query goes to DNS resolver (usually your ISP or 8.8.8.8)
   ↓ (not found)
4. Resolver asks root nameservers: "Who handles .com?"
   ↓
5. Root says: "Ask the .com TLD servers"
   ↓
6. Resolver asks .com TLD: "Who handles example.com?"
   ↓
7. TLD says: "Ask ns1.example.com"
   ↓
8. Resolver asks example.com's nameserver: "What's www.example.com?"
   ↓
9. Nameserver returns: "93.184.216.34"
   ↓
10. IP gets cached at every level for next time

This looks slow, but caching makes it fast. Most lookups hit a cache and return instantly.

Domain name anatomy

https://blog.example.com/posts/hello
└─┬──┘ └─┬─┘└───┬───┘└─┬┘└────┬────┘
  │     │      │     │      │
protocol│   domain   │    path
     subdomain      TLD

Part	Example	What it is
TLD (Top Level Domain)	`.com`, `.org`, `.io`	Managed by registries
Domain	`example`	The name you buy
Subdomain	`blog`, `www`, `api`	You create these (free, unlimited)

You buy: example.com You get for free: www.example.com, api.example.com, anything.example.com

DNS record types

DNS records are instructions stored at your nameserver. Different record types do different things.

A Record

Maps a domain to an IPv4 address.

example.com → 93.184.216.34

Use for: Pointing your domain to a server’s IP address.

AAAA Record

Maps a domain to an IPv6 address.

example.com → 2606:2800:220:1:248:1893:25c8:1946

CNAME Record

Maps a domain to another domain (an alias).

www.example.com → example.com
blog.example.com → myapp.vercel.app

Use for: Subdomains, pointing to hosting platforms.

Important: CNAME cannot be used on the root domain (example.com). Only on subdomains (www.example.com).

MX Record

Mail exchange—where to deliver email.

example.com MX → mail.example.com (priority 10)

Use for: Setting up email (Google Workspace, Fastmail, etc.)

TXT Record

Text data, often for verification.

example.com TXT → "v=spf1 include:_spf.google.com ~all"

Use for: Domain verification, email security (SPF, DKIM), proving you own the domain.

NS Record

Nameserver—which servers are authoritative for this domain.

example.com NS → ns1.cloudflare.com

Use for: Delegating DNS to a different provider.

Common DNS tasks

Pointing a domain to your app

Scenario: You bought myapp.com and want it to load your app hosted on Vercel/Railway/Render.

Option 1: CNAME (for subdomains)

www.myapp.com CNAME → cname.vercel-dns.com

Option 2: A record (for root domain)

myapp.com A → 76.76.21.21

Your hosting provider tells you which records to add.

Setting up a subdomain

Want api.myapp.com to point somewhere different?

api.myapp.com A → 123.45.67.89

Or point it to another service:

api.myapp.com CNAME → my-api.railway.app

Verifying domain ownership

Services like Google, Mailchimp, or Stripe ask you to prove you own a domain. They give you a TXT record to add:

myapp.com TXT → "google-site-verification=abc123..."

Once you add it and they can query it, ownership is verified.

Where to manage DNS

Domain registrar

Where you bought the domain: Namecheap, Google Domains, GoDaddy, Cloudflare.

Most registrars include basic DNS hosting. You can manage records there.

Dedicated DNS hosting

For more features (faster propagation, DDoS protection, analytics):

Cloudflare (free tier, very popular)
AWS Route 53
Google Cloud DNS

To use these, you change your domain’s nameservers at your registrar to point to the DNS host.

Your hosting provider

Vercel, Netlify, Railway often handle DNS for you if you let them manage the domain.

DNS propagation

When you change a DNS record, it doesn’t update instantly everywhere. The old value is cached.

TTL (Time To Live) controls how long caches keep the old value. Measured in seconds.

TTL	Meaning
300	5 minutes
3600	1 hour
86400	24 hours

Before making changes: Lower TTL to 300 a day ahead. Then caches expire faster when you make the real change.

Propagation time: Usually 5 minutes to 48 hours. Most changes are visible within an hour.

Check propagation: Use dnschecker.org or whatsmydns.net to see if your change has propagated worldwide.

Debugging DNS issues

“Site not loading” after DNS change

Check propagation: Has it spread to your location yet?

Flush local cache:

bash

# Mac
sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

# Windows
ipconfig /flushdns

Try a different DNS resolver: Temporarily use 8.8.8.8 (Google) or 1.1.1.1 (Cloudflare)

Check what DNS returns