Public and private addresses
Your router gives each device at home a private address such as 192.168.1.20 or 10.0.0.5. Those only work inside your network. When a device goes online, the router swaps the private address for your public one, so every device in the house shares it. That swap is called NAT.
Some providers, especially mobile networks, share one public IPv4 address between many customers using carrier-grade NAT. Their customers get addresses from 100.64.0.0/10 on the inside. A website then sees an address used by hundreds of people at once.
Why your IP address changes
Most home connections get a dynamic address that can change when the modem restarts or the lease runs out. Mobile connections change more often. Business plans can include a static address that stays the same, which is useful for remote access and mail servers.
A VPN replaces your address with one belonging to the VPN provider. Websites then see the VPN's address and location instead of yours.
What your IP address reveals
Your provider, the network block it belongs to and a rough location, usually the city of the provider's equipment. It does not reveal your name, street address or which device you are using; only your provider holds the records that link an address to an account.
Questions
- Is my IP address the same as my device's address?
- Usually not for IPv4: your device has a private address and the router shares one public address. With IPv6 each device normally has its own public address.
- Can I hide my IP address?
- A VPN or Tor routes your traffic through another network so sites see that network's address. Your provider still sees that you connect to the VPN or Tor.