A free guide to the Domain Name System

Learn DNS

How a name becomes an address. Eight parts, from HOSTS.TXT to DNSSEC, encrypted transports, and the records you actually publish.

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Every lookup starts the same way: something asks for a name, and DNS answers with data. These lessons follow that system in order. Part 1 is the history that explains the odd corners. Part 2 is the protocol. Later parts cover registration, attacks, operations, and what is changing now.

New to DNS? Start with the pre-DNS era. If you already know what a resolver is, the resolution process is the shortest path into the machinery.

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Part 1 Origins & History of DNS

How the internet learned to remember names, from ARPANET's HOSTS.TXT file to the global Domain Name System still in use.

1.1 The Pre-DNS Era

1.2 The Invention of DNS

1.3 Early Infrastructure

1.4 The DNS Wars

1.5 Timeline of Major DNS Milestones 12 min

A timeline from ARPANET in 1969 to today, covering the standards, institutions, and disputes that shaped the Domain Name System.

Part 2 How DNS Works

How DNS answers a lookup: names, the resolution path, record types, caching, the root, zone transfers, and the wire format.

2.1 DNS Fundamentals 10 min

Names, labels, the DNS tree, zones versus domains, delegation, and fully qualified names — the parts every later lesson builds on.

2.2 The Resolution Process 12 min

Follow a DNS query step by step from browser cache through recursive resolvers to authoritative nameservers — understand how domain names become IP addresses.

2.3 DNS Record Types 15 min

A comprehensive guide to DNS record types — A, AAAA, CNAME, MX, NS, TXT, SOA, SRV, CAA, PTR, DNSSEC records, and the new SVCB/HTTPS records.

2.4 DNS Caching and TTL 11 min

How DNS caches answers at every layer, how TTL and negative caching work, and how to change records without serving stale data.

2.5 Authoritative vs Recursive Resolvers 10 min

Understanding the two types of DNS servers — authoritative nameservers and recursive resolvers — and how they work together.

2.6 The Root Zone and Root Servers 12 min

The 13 root-server identities, who operates them, how anycast spreads them out, and how the root zone is signed and published.

2.7 Zone Files and Zone Transfers 12 min

Zone file format and syntax, SOA record deep dive, AXFR and IXFR transfers, TSIG authentication, and modern zone management.

2.8 DNS Protocol Deep Dive 14 min

DNS message format, wire encoding, UDP vs TCP, EDNS(0), port 53, and message compression — understanding DNS at the packet level.

Part 3 The Domain Ecosystem

The business and operational side of domain names — how domains are named, registered, transferred, and managed across the registry-registrar system.

3.1 Domain Name Anatomy 10 min

SLDs, TLDs, subdomains, FQDNs, label rules, and internationalized domain names — every piece of a domain name explained.

3.2 TLD Types 11 min

Generic, country code, sponsored, and new gTLDs — the taxonomy of top-level domains and the expansion that changed the namespace.

3.3 The Domain Lifecycle 11 min

From registration to expiry, redemption, and pending delete — every phase a domain passes through, with timing and implications.

3.4 Registries, Registrars, and Resellers 12 min

The three-tier system behind domain registration — how registries, ICANN-accredited registrars, and resellers work together.

3.5 WHOIS and RDAP 12 min

Domain ownership lookup from the legacy WHOIS protocol to its modern RDAP replacement — history, data fields, GDPR impact, and privacy services.

3.6 Domain Transfers 10 min

Auth codes, transfer locks, the five-step transfer process, disputes, and bulk transfers — everything about moving domains between registrars.

3.7 DNS Hosting vs Domain Registration 9 min

Why domain registration and DNS hosting are separate concerns, how to use third-party DNS with any registrar, and when each option makes sense.

3.8 EPP Deep Dive 12 min

The Extensible Provisioning Protocol — how registrars communicate with registries to create, manage, transfer, and delete domain names.

Part 4 DNS Security

From foundational vulnerabilities to encrypted transport and protective DNS — how the internet's naming system learned to defend itself.

4.1 DNS Vulnerabilities 12 min

The fundamental security flaws in DNS — from cache poisoning and the Kaminsky attack to amplification DDoS, tunneling, and domain name abuse.

4.2 DNSSEC 14 min

The cryptographic chain of trust that authenticates DNS — key types, record types, the validation process, and why adoption remains stubbornly low.

4.3 DNS-over-HTTPS (DoH) 12 min

How DNS queries got wrapped in HTTPS — the protocol, browser adoption, provider landscape, and the fierce centralization debate.

4.4 DNS-over-TLS (DoT) 10 min

The first standardized encrypted DNS transport — how it works, where it's deployed, and how it compares to DNS-over-HTTPS.

4.5 DNS-over-QUIC (DoQ) 10 min

The newest encrypted DNS transport — how QUIC improves on TLS-based protocols, what RFC 9250 defines, and where adoption stands today.

4.6 DNS Hijacking and BGP Attacks 11 min

When attackers bypass DNS itself: registrar compromise, BGP hijacking, route manipulation, and other attacks on internet routing.

4.7 Protective DNS and Threat Intelligence 12 min

Using DNS as a defensive weapon — threat blocking, response policy zones, CAA records, and DNS monitoring for security operations.

Part 5 Modern DNS Infrastructure

How DNS powers today's internet — from CDNs and load balancing to containers, edge computing, and zero-configuration networking.

5.1 CDN and DNS 10 min

How content delivery networks use anycast, GeoDNS, and EDNS Client Subnet to steer each user toward a nearby edge server.

5.2 DNS Load Balancing and Failover 11 min

Round-robin DNS, weighted answers, health-check failover, and the real limits of balancing traffic with DNS records alone.

5.3 Split-Horizon DNS 9 min

Internal vs external DNS views — how organizations serve different answers to different clients based on network location.

5.4 Dynamic DNS (DDNS) 10 min

Automatic DNS updates for changing IP addresses — from RFC 2136 protocol mechanics to consumer DDNS services and enterprise deployments.

5.5 Multicast DNS and DNS Service Discovery 10 min

mDNS, DNS-SD, and zero-configuration networking — how your devices find printers, AirPlay speakers, and each other without any server.

5.6 DNS in Containers and Kubernetes 12 min

CoreDNS, Kubernetes service discovery, pod DNS policies, Docker's embedded DNS, and service mesh DNS with Consul and Istio.

5.7 Serverless DNS and Edge Computing 10 min

Programmable DNS at the edge, policy written as code, and how serverless workers change where each DNS decision is made.

Part 6 The Domain Industry

The business, governance, and legal side of domains — from ICANN policy and gTLD programs to domain investing, valuation, privacy, and legal disputes.

6.1 ICANN Governance 12 min

What ICANN is and isn't, how it's structured, the policy development process, the IANA transition, and the controversies that have defined internet governance.

6.2 The New gTLD Program 12 min

How ICANN's 2012 expansion created hundreds of new top-level domains — the process, controversies, brand TLDs, and what comes next.

6.3 Domain Investing and the Aftermarket 12 min

How domain investing works: hand registrations, drops, auctions, parking, famous sales, and the aftermarket that trades names.

6.4 Domain Valuation Methodologies 11 min

How domain names are valued — comparable sales, heuristic scoring, AI approaches, automated tools, and why pricing domains remains more art than science.

6.5 Domain Privacy and Proxy Services 11 min

Why domain privacy matters, the difference between privacy and proxy registration, GDPR's seismic impact on WHOIS, and ICANN's ongoing policy battles.

6.6 Legal Aspects 13 min

Domain dispute resolution — UDRP, URS, the ACPA, trademark law, reverse domain name hijacking, and the cases that shaped the rules.

6.7 Country Code Politics 12 min

The geopolitical drama of ccTLDs — delegation battles, the .io controversy, Soviet .su, country TLDs gone global, and what happens when nations vanish.

Part 7 Practical DNS for Developers

Hands-on DNS for people who ship software: publish a zone, fix mail, debug lookups, and automate the records you rely on.

7.1 Setting Up DNS for a Website 12 min

The complete practical walkthrough — from buying a domain to serving your first page, with every DNS decision explained.

7.2 Email DNS 14 min

MX, SPF, DKIM, and DMARC: the DNS records that decide whether a message reaches the inbox or is rejected outright as spam.

7.3 DNS Debugging Tools 14 min

Master dig, nslookup, drill, dog, and online diagnostic tools — with practical debugging scenarios and output walkthroughs.

7.4 Common DNS Misconfigurations 12 min

The mistakes everyone makes — CNAME at apex, missing trailing dots, lame delegation, and more — with diagnosis and fixes.

7.5 DNS Automation and Infrastructure as Code 13 min

Manage DNS with Terraform, OctoDNS, and DNSControl so zone changes are reviewed in Git and applied the same way each time.

7.6 API-Driven DNS Management 13 min

Programmatic DNS control with provider APIs such as Cloudflare and Route 53, and how that differs from registration lookups.

7.7 DNS and CI/CD Pipelines 13 min

Automated SSL provisioning, blue-green deployments, canary releases, and zero-downtime migrations — DNS as a deployment primitive.

Part 8 The Future of DNS

Where DNS and domain naming are headed — from blockchain-based alternatives to quantum-resistant cryptography and the rise of AI agents.

8.1 Decentralized Naming 12 min

Blockchain-based alternatives to DNS — ENS, Handshake, Unstoppable Domains, Namecoin, and whether they'll ever replace the traditional domain name system.

8.2 AI Agents and DNS 11 min

How autonomous agents discover and authenticate each other, and why DNS is becoming the discovery and identity layer they use.

8.3 Encrypted Client Hello (ECH) 10 min

The last privacy gap in HTTPS — how ECH encrypts the SNI field, its deployment status, and implications for DNS, CDNs, and censorship resistance.

8.4 SVCB and HTTPS Record Types 10 min

The newest DNS record types defined in RFC 9460 — service binding, HTTPS records, eliminating redirects, and distributing ECH keys.

8.5 The Next Billion Domains 10 min

Growth projections, the fastest-growing TLDs, domains in developing markets, AI-generated names, and the rise of programmatic domain registration.

8.6 Quantum Computing and DNS 11 min

How quantum computers threaten DNSSEC's cryptographic foundations, post-quantum cryptography standards, and the timeline for preparing DNS infrastructure.