The difference at a glance
A public IP address is routable on the internet. It represents the connection that websites and online services communicate with. Your internet provider, mobile carrier, employer or VPN service normally assigns that address.
A private IP address works only inside a local network. A home router gives private addresses to phones, laptops, televisions and other connected devices so they can communicate without each one needing a separate public IPv4 address.
Common private address ranges
Standards reserve several IPv4 ranges for private networks. Addresses in these ranges are not routed across the public internet, although the same private address can be reused independently in millions of homes and offices.
- 10.0.0.0 through 10.255.255.255
- 172.16.0.0 through 172.31.255.255
- 192.168.0.0 through 192.168.255.255
- IPv6 commonly uses unique local or link-local addresses for local communication
How a router connects the two
Most home and small-office routers use network address translation. The router keeps track of connections from private devices and translates them to a shared public IPv4 address. Replies are then sent back to the correct device.
Carrier-grade NAT applies the same idea at a larger scale. A mobile or broadband provider may let several customers share a public IPv4 address, which means the address visible online may not belong exclusively to one household.
Which address should you use?
Use your private address when configuring a device or service inside your own network. Use your public address when checking what websites see or when diagnosing an internet-facing connection.
Publishing services from a home network requires careful router and firewall configuration. Opening ports can increase security risk, so use authenticated, updated software and avoid exposing administrative interfaces directly to the internet.