FernTool

Public vs private IP address

Every device on the internet ultimately talks using IP addresses, but the address your laptop uses at home is not the address the rest of the world sees. One is private, one is public. Your public IP is on the FernTool homepage; your private IP is in your device’s network settings (here’s how to find it).

What is a public IP address?

A public IP is globally unique and routable on the internet. Your ISP assigns it to your router (or, on mobile, to a gateway shared by many users). Websites, game servers and email servers see this address when you connect. It reveals your ISP and an approximate location — typically the right country and often the right city — but not your name or street address.

Public addresses are allocated by the five regional internet registries (AFRINIC for Africa, RIPE NCC for Europe, ARIN for North America, APNIC for Asia-Pacific and LACNIC for Latin America) to networks, which then assign them to customers. That chain is why an IP lookup can tell you which organisation and ASN own an address.

What is a private IP address?

A private IP is used only inside a local network — your home, office or a cloud VPC. The same private addresses are reused in millions of networks at once, so they can’t be routed on the internet. RFC 1918 reserves three IPv4 blocks for this:

10.0.0.0/8
10.0.0.0 – 10.255.255.255 (16.7 million addresses)
172.16.0.0/12
172.16.0.0 – 172.31.255.255 (1 million)
192.168.0.0/16
192.168.0.0 – 192.168.255.255 (65,536)

Home routers almost always use 192.168.x.x or 10.x.x.x. In IPv6 the equivalent is unique local addresses in fc00::/7 (in practice fd00::/8), plus link-local fe80::/10 addresses that every interface has.

Other non-public ranges you might see

The FernTool IP lookup classifies any address as public, private, loopback, link-local, CGNAT, multicast or reserved.

How public and private IPs work together: NAT

Your router performs Network Address Translation (NAT). When your phone (192.168.1.20) requests a web page, the router rewrites the packet so it appears to come from your public IP, remembers the mapping, and sends the reply back to the right device. This is why every device at home shows the same public IP.

NAT has a side effect: devices behind it can’t be reached from outside unless you set up port forwarding on the router. That’s fine for browsing but matters for hosting a game server, a CCTV recorder or a home server.

Public vs private at a glance

Who assigns it
ISP vs your router (DHCP)
Unique?
Globally vs only within your network
Seen by websites?
Yes vs never
Reveals location?
Approximate vs no
Changes?
When the ISP reassigns vs when the router reassigns
Cost
Static public IPs often cost extra vs free

Which one do I need?

Static vs dynamic public IPs

Most home connections receive a dynamic public IP that can change when the router reconnects. A static IP stays the same and is usually a paid add-on. If you need a stable address but your ISP won’t give one, dynamic DNS services can map a hostname to your changing IP.

What about CGNAT?

On mobile networks and some fixed-wireless ISPs, your router itself gets a private-style address (often in 100.64.0.0/10) and the ISP performs a second NAT, sharing one public IP among many customers. That’s carrier-grade NAT. A quick test: compare the WAN IP in your router with the IP on FernTool. If they differ, you’re behind CGNAT. IPv6 avoids the problem altogether — learn about IPv6.

Is it safe to share my IP?

Sharing your private IP is harmless — it means nothing outside your network. Sharing your public IP reveals your ISP and rough location, and exposes your router to scans (which happen to every public IP anyway). Keep your router firmware updated and don’t forward ports you don’t need. To hide your public IP, see how to hide your IP address.

Frequently asked questions

Is 192.168.1.1 a public or private IP?

192.168.1.1 is a private IP from the 192.168.0.0/16 range. It is commonly used as a home router address and cannot be reached from the internet.

What are the private IP ranges?

10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 for IPv4, and fc00::/7 for IPv6.

Why do all my devices show the same public IP?

Your router uses NAT to share one public IP among all devices on your network.

Can someone find me from my public IP?

They can see your ISP and approximate area. Only your ISP can link the IP to your account, typically only under legal process.

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