DNS Explained
Learn how the Domain Name System translates human-readable domain names into IP addresses your computer can use.
What is DNS?
DNS (Domain Name System) is often called the "phone book of the internet." It translates human-friendly domain names (like codescompiler.com) into machine-readable IP addresses (like 185.199.108.153).
Without DNS, you'd have to memorize IP addresses instead of domain names to visit any website.
How DNS Resolution Works
- You type a URL — Your browser checks its local cache. If found, done!
- Recursive Resolver — Your ISP's DNS server (or Google's 8.8.8.8) receives the query.
- Root Name Server — Directs the resolver to the TLD server (e.g., .com, .org, .net).
- TLD Name Server — Directs the resolver to the domain's authoritative name server.
- Authoritative Name Server — Returns the actual IP address.
- Response — The IP address is returned to your browser, which connects to the server.
DNS Record Types
- A Record — Maps a domain to an IPv4 address.
- AAAA Record — Maps a domain to an IPv6 address.
- CNAME — Alias for another domain (e.g., www → yoursite.com).
- MX Record — Specifies mail servers for the domain.
- TXT Record — Stores text data (used for verification, SPF, DKIM).
- NS Record — Specifies authoritative name servers for the domain.
- TTL (Time To Live) — How long a DNS record is cached before refreshing.
Public DNS Servers
- Google — 8.8.8.8 and 8.8.4.4
- Cloudflare — 1.1.1.1 and 1.0.0.1 (privacy-focused, very fast)
- OpenDNS — 208.67.222.222
DNS Security
- DNS Spoofing / Cache Poisoning — An attacker inserts false DNS entries to redirect users to malicious sites.
- DNSSEC — DNS Security Extensions add cryptographic signatures to verify DNS responses.
- DNS over HTTPS (DoH) — Encrypts DNS queries to prevent snooping.
What's Next?
Learn how web servers handle requests with HTTP & HTTPS, or explore how attackers manipulate DNS in Cyber Security.