Public IP
Public IP Address
The globally unique, internet-routable address your ISP assigns to your router — the address every website and server sees when your household connects to the internet, shared by all devices on your LAN via NAT.
Your public IP address is assigned by your ISP and is visible to every server you connect to. It sits on the WAN side of your router. When any device on your network initiates a connection to the internet, your router rewrites the source IP from the device's private address to your public IP (NAT). The destination server sees the public IP and sends its response back to it. Your router then looks up its NAT table and forwards the response to the correct internal device. Most households have one public IPv4 address shared by all devices.
Public IP vs private IP
| Property | Public IP | Private IP |
|---|---|---|
| Assigned by | ISP | Your router (DHCP) |
| Globally unique | Yes | No (reused across networks) |
| Routed on internet | Yes | No |
| Visible to websites | Yes | No |
| Typically changes | Yes (dynamic) or No (static) | Sometimes (DHCP lease) |
Static vs dynamic public IP
Most residential connections use a dynamic public IP — it can change when your modem reconnects or on a periodic schedule set by your ISP. Business plans and paid add-ons offer a static (fixed) public IP that never changes. Static IPs are needed for hosting servers, remote access (if not using a VPN), gaming servers, and any service where others must reach you by IP. If your router's WAN IP is in the 100.64.0.0/10 range, your ISP is using CGNAT — you're sharing an IP with other customers and can't use port forwarding without contacting your ISP.
Frequently Asked Questions
Is my public IP address the same as my device's IP address?
No. Your device has a private IP (192.168.x.x) assigned by your router. Your router has a public IP assigned by your ISP. Websites see your public IP — to find it, search "what is my IP" or run a speed test.
Does my public IP address change?
Usually yes — residential ISPs assign dynamic IPs that change on reconnect or on schedule. Static IPs (fixed) are available as paid add-ons or on business plans. Dynamic DNS (DDNS) services let you use a hostname that automatically tracks your changing IP.
What is CGNAT and how does it affect my public IP?
CGNAT shares one public IPv4 address among multiple ISP customers. If your router's WAN IP starts with 100.64–100.127, you're behind CGNAT. Port forwarding won't work. Request a dedicated IP from your ISP or use IPv6 to work around it.