Guide
Public vs private IP addresses
Learn the difference between public and private IP addresses, which ranges are reserved, how NAT connects them, and how to find each one on your network.
On this page
The core difference
A public IP address is globally unique and routable across the internet. A private IP address is only meaningful inside one local network; routers on the public internet are required to drop packets addressed to it. Your router holds both: a public address facing your ISP, and a private one facing your devices.
Think of it as an office building. The public IP is the street address that mail arrives at; the private IPs are the internal room numbers that only the mailroom understands.
Reserved private ranges
| Range | Addresses | Typical use |
|---|---|---|
| 10.0.0.0/8 | 10.0.0.0 – 10.255.255.255 | Large corporate and campus networks |
| 172.16.0.0/12 | 172.16.0.0 – 172.31.255.255 | Medium business networks, Docker defaults |
| 192.168.0.0/16 | 192.168.0.0 – 192.168.255.255 | Home routers and small offices |
| 100.64.0.0/10 | 100.64.0.0 – 100.127.255.255 | Carrier-grade NAT (shared ISP space) |
| 169.254.0.0/16 | 169.254.0.0 – 169.254.255.255 | Link-local fallback when DHCP fails |
| 127.0.0.0/8 | 127.0.0.1 and friends | Loopback — the device talking to itself |
| fc00::/7, fe80::/10 | IPv6 unique-local and link-local | The IPv6 equivalents of the above |
If our checker reports a private address, the request never reached the internet the way you expected — usually a misconfigured proxy, a captive portal or a local test environment.
How NAT bridges the two
Network address translation lets many private devices share one public address. When your phone opens a connection, the router rewrites the source address to the public IP and records the mapping in a translation table. Replies come back to the public address, and the router uses the table to deliver them to the right device.
The side effect is that inbound connections have nowhere to go by default — which is why hosting a game server or security camera requires port forwarding, and why CGNAT connections cannot do it at all.
How to find each address
Your public address
Open the home page. The large number is what the internet sees.
Your private address
- Windows: open Command Prompt and run
ipconfig; look for IPv4 Address. - macOS: System Settings → Network → Details, or run
ipconfig getifaddr en0. - Linux: run
ip addr showorhostname -I. - iOS / Android: Wi-Fi settings → tap the connected network → IP address.
When each one matters
Use the private address to reach a printer, NAS or dev server on your own LAN, and to set DHCP reservations. Use the public address for firewall allowlists, remote access rules, API restrictions and DNS records. Mixing them up is the single most common cause of "it works at home but not from outside" support tickets.
Not sure which type you are looking at? Paste it into the IP lookup tool — reserved ranges are identified instantly.
Frequently asked questions
Is 192.168.1.1 a public IP address?
No. It sits in the reserved 192.168.0.0/16 private range and is normally the LAN address of a home router. It cannot be reached from the internet.
Can two networks use the same private IP?
Yes, and they usually do. Millions of homes use 192.168.1.10 simultaneously because private addresses only need to be unique within their own network.
Do I need a public IP to browse the web?
You need one, but it can be shared. NAT and CGNAT let many users browse through a single public address.
Keep reading
Check any other IP address
Investigating a suspicious login, a spam email header or a server log entry? Run any IPv4 or IPv6 address through the same geolocation and proxy checks.