IP Address
Internet Protocol address
A unique numerical label assigned to every device on a network — your internet identity.
An IP address is a unique numerical label assigned to every device on a network. IPv4 addresses look like 192.168.1.1; IPv6 addresses look like 2001:db8::1. Your ISP assigns you a public IP address visible to the internet; your router assigns private IP addresses to devices on your home network.
IPv4 address structure
An IPv4 address is 32 bits long, written as four decimal numbers (octets) separated by dots — for example, 203.0.113.45. Each octet ranges from 0 to 255, giving a theoretical total of about 4.3 billion unique addresses. In practice, large blocks are reserved for private use, special purposes, and infrastructure, leaving roughly 3.7 billion publicly routable addresses — a pool that was officially exhausted by IANA in 2011.
Public vs private IP ranges
Three IPv4 ranges are permanently reserved for private (non-routable) use. Traffic using these addresses never appears on the public internet; your router translates between them and your single public IP using NAT.
- 10.0.0.0/8 — 10.x.x.x; 16.7 million addresses; common in enterprise and ISP carrier-grade NAT
- 172.16.0.0/12 — 172.16.x.x through 172.31.x.x; used by some routers and Docker
- 192.168.0.0/16 — 192.168.x.x; the range used by virtually every home router
Special addresses
- 127.0.0.1 — loopback (localhost); traffic to this address never leaves the device; used for local development and self-testing
- 169.254.x.x — APIPA (Automatic Private IP Addressing); assigned automatically when a device cannot reach a DHCP server; seeing this address means your device failed to get an IP from your router
- 255.255.255.255 — limited broadcast; sends to all devices on the local network segment
IPv6: the successor
IPv6 uses 128 bits, written as eight groups of four hexadecimal digits separated by colons: 2001:0db8:85a3:0000:0000:8a2e:0370:7334. This provides 340 undecillion (3.4 × 1038) addresses — enough to assign billions of addresses to every person on Earth. Most ISPs now dual-stack (assign both an IPv4 and IPv6 address) and most major websites support IPv6. Devices on IPv6 connections often reach IPv6-enabled services faster because they bypass NAT entirely.
How your device gets an IP address
DHCP (Dynamic Host Configuration Protocol) is the standard mechanism: when your device connects to a network, it broadcasts a request; your router's DHCP server responds with an available IP address, subnet mask, gateway, and DNS server. This lease typically lasts 24 hours for home networks, after which the device renews it (and usually gets the same address back).
Static IP assignment skips DHCP — you manually configure the address on the device or reserve it in the router's DHCP table by MAC address. Static assignment is useful for printers, NAS devices, and anything you need to reach by a predictable local address.
Finding your local vs public IP
Your local (private) IP — the one your router assigned — can be found in your device's network settings, or by running ipconfig (Windows) or ifconfig / ip addr (macOS/Linux). Look for the address in the 192.168.x.x, 10.x.x.x, or 172.16–31.x.x range.
Your public IP — what the internet sees — is visible by searching "what is my IP" in any browser, or visiting a tool like SpeedTestHQ. This is the address your ISP assigned to your router's WAN port.
Dynamic vs static public IP
Most residential plans use a dynamic public IP: it can change whenever your modem reboots, after a DHCP lease expires (often 24–48 hours), or when the ISP reassigns addresses. For most users this is invisible — browsing, streaming, and gaming all work regardless.
A static public IP never changes. You would need one if you host a web or game server at home, use a VPN that whitelists by IP, or need reliable remote desktop access without a dynamic DNS service. ISPs typically charge $5–15/month extra for a static public IP on residential plans; business plans often include one.
Frequently Asked Questions
How do I find my public IP address?
Search 'what is my IP' in any browser — the result page shows your current public IP. This is the address websites see when you connect. Your router's admin page shows your public IP under WAN status.
Does my IP address show my location?
Your IP can be traced to your ISP and roughly your city or region — not your exact address. ISPs maintain records linking IPs to account holders, accessible to law enforcement with a warrant. For precise location, GPS or Wi-Fi geolocation is required.