Guides
Instantly see what your IP address is, plus free IP lookup, WHOIS, DNS, subnet calculator and IP converter tools.
IP Basics
What an IP address is, IPv4 structure, public/private, subnetting
IP Types & Special Addresses
Static/dynamic, unicast/multicast/broadcast/anycast, loopback and other special ranges
IPv6
IPv6 notation, differences from IPv4, transition tech (articles)
History of IP
From ARPANET to IPv4 exhaustion, the role of IANA/RIRs
Whois / RDAP / DNS
How WHOIS/RDAP works, DNS basics, reverse lookups
- How WHOIS, RDAP and DNS Work (and How They Differ)
- What Is Reverse DNS (PTR Records)?
- DNS Record Types Explained (A, AAAA, CNAME, MX, TXT, NS)
- DNSSEC Explained: Signing the DNS
- SPF, DKIM and DMARC Explained
- CAA Records: Controlling Who Can Issue Your Certificates
- DNS TTL Explained: Caching and Propagation
- What Is an ASN (Autonomous System Number)?
- BGP Routing Basics
- RPKI and ROA Explained
Linux Commands
ip, ss, netstat, dig, traceroute… old vs new commands
Windows Commands
ipconfig, netstat, and PowerShell networking cmdlets
Programming
IP fetch/validate/convert samples in Go/Python/JS/PHP/C…
Network & Security
NAT, proxies, VPNs, IP spoofing, reputation
- Proxies, VPNs and NAT: How Your IP Appears
- How to Hide My IP Address (VPN, Proxy, Tor)
- What Can Someone Find From My IP Address?
- How the SSL/TLS Certificate Chain Works
- How to Check SSL Certificate Expiry (and Never Get Caught Out)
- TLS Versions Explained: 1.0 to 1.3
- ACME and Let's Encrypt: Automatic Certificates
- HTTP Security Headers Explained
- X-Forwarded-For: Getting the Real Client IP Behind a Proxy
- CGNAT Explained: Why You Share a Public IP
- Certificate Transparency (CT) and SCTs Explained
- Certificate Revocation: OCSP, CRL and Stapling
- Can Someone Track Me by My IP Address?