DNS (Domain Name System) translates human-readable domain names into IP addresses. When you type google.com, DNS figures out that means 142.250.185.78 and sends your request there.

It’s the phone book of the internet.

How it works (simplified)

1. You type example.com in your browser
2. Your computer asks a DNS resolver: “What’s the IP for example.com?”
3. The resolver checks its cache. If not cached, it asks the root servers → .com servers → example.com’s nameservers
4. The nameserver responds: “It’s 93.184.216.34”
5. Your browser connects to that IP address
6. The result is cached so the next request is instant

This whole process takes milliseconds.

DNS record types

Record	What it does	Example
A	Maps domain to IPv4 address	example.com → 93.184.216.34
AAAA	Maps domain to IPv6 address	example.com → 2606:2800:220:1:...
CNAME	Alias to another domain	www.example.com → example.com
MX	Mail server	example.com → mail.example.com
TXT	Text data (verification, SPF, etc.)	v=spf1 include:_spf.google.com
NS	Nameserver for the domain	example.com → ns1.provider.com

A records are the most common — they point your domain to a server IP.

CNAME records are aliases — www.example.com points to example.com, which has the actual A record.

Common DNS tasks

Point a domain to a server:

Type: A
Name: @           (or example.com)
Value: 93.184.216.34
TTL: 3600

Point www to the same place:

Type: CNAME
Name: www
Value: example.com
TTL: 3600

Verify domain ownership (Google, Vercel, etc.):

Type: TXT
Name: @
Value: google-site-verification=abc123...

DNS propagation

When you change DNS records, the change doesn’t happen instantly. Old records are cached by DNS servers worldwide.

• TTL (Time To Live) controls how long records are cached
• Low TTL (300 = 5 min): changes propagate fast, more DNS lookups
• High TTL (86400 = 24 hours): changes are slow, fewer lookups

Before making changes: lower the TTL to 300 a day in advance. After the change propagates, raise it back.

Checking propagation:

# Check from your machine
dig example.com
nslookup example.com

# Check from specific DNS server
dig @8.8.8.8 example.com
dig @1.1.1.1 example.com

Or use dnschecker.org to check from multiple locations worldwide.

Common DNS issues

“DNS not propagated yet” — wait. It can take up to 48 hours (usually much less).

“Site not working after domain change” — check with dig:

dig example.com +short
# Should show your server's IP

“Email not working” — check MX records:

dig example.com MX +short

“SSL certificate error after DNS change” — the new server needs its own SSL certificate. If using Let’s Encrypt, it needs DNS to be pointing to it first.

DNS providers

Your domain registrar usually provides DNS, but you can use a dedicated DNS provider for better performance:

• Cloudflare — free, fast, DDoS protection
• Route 53 — AWS, reliable, integrates with AWS services
• Google Cloud DNS — similar to Route 53
• Your registrar — Namecheap, GoDaddy, etc. (fine for simple setups)