What an IP address actually identifies
An IP address identifies a network interface within a particular Internet Protocol scope so packets can be delivered toward it. “Interface” matters: the Wi-Fi and mobile sides of one phone can have different addresses, and a virtual interface created by a VPN can add another. “Scope” matters too: an address that is valid inside a home network may have no meaning on the public internet.
Addresses are not permanent names. A router can assign a new local address after a reconnect, a provider can change the public address for a customer, and temporary IPv6 addresses can rotate. Conversely, one public IPv4 address may represent many devices—or even many customers—behind address translation.
How a packet uses source and destination addresses
When an app sends data, the IP packet contains a source address and a destination address. Routers examine the destination prefix and choose a next hop. Each router moves the packet closer to a network that can deliver it to the destination interface; the return traffic uses the addressing information available on the reverse path.
The source seen by the destination is not always the address Android shows on Wi-Fi. A home router may translate private IPv4 connections to its public address. A mobile carrier may add carrier-grade translation. A VPN normally presents its exit server as the public source. This is why an address checker describes the path that reached it, not every address held by the phone.
Continue with Public vs private IP addresses, compare it with IPv4 vs IPv6: what changes?, or use How IP address lookup works for the next practical step.
Public, private, and local scope
| Address type | Where it is meaningful | Typical example of who assigns it |
|---|---|---|
| Public IP | Across public internet routing | Internet provider, mobile carrier, hosting network, or VPN |
| Private IPv4 | Inside a home, office, or other local network | Router or network administrator |
| IPv6 link-local | On the directly connected link | Created for the interface under IPv6 rules |
| IPv6 unique local | Inside selected private networks | Organization or local network design |
Private IPv4 ranges are specifically reserved for private internets, so unrelated networks can reuse the same values. They are not ordinary public destinations. IPv6 uses several scopes rather than simply copying the IPv4 public/private model, which is why labeling the type is more helpful than asking whether every address is “public.”
The protocol details in this guide follow RFC 5737 — IPv4 Address Blocks Reserved for Documentation and RFC 3849 — IPv6 Address Prefix Reserved for Documentation; use those primary specifications when you need exact terminology or edge-case behavior.
IPv4 and IPv6 can coexist
IPv4 carries 32-bit addresses, commonly written as four decimal numbers. IPv6 carries 128-bit addresses written in hexadecimal groups. The larger address space is the most visible difference, but IPv6 also defines a redesigned base header and different operational behavior.
Many current networks are dual stack: they offer both protocols and let the operating system and application choose a reachable path. A website might receive an IPv6 connection while another service uses IPv4. If one protocol is absent in a test, check the current network and destination before concluding that the device never supports it.
A home Wi-Fi example from device to website
- The phone joins Wi-Fi
The router provides local configuration, often including a private IPv4 address, gateway, and DNS information.
- The app resolves a name
DNS returns address records for the destination. The app and Android select a usable IPv4 or IPv6 path.
- Traffic reaches the router
For private IPv4, the router commonly translates the connection to a public source. IPv6 may follow a different routed path.
- The website records a public source
That value can describe the router, provider gateway, or VPN exit—not the phone’s private Wi-Fi address.
Switching to mobile data replaces the first part of this path. Connecting a VPN can change the public source and resolver behavior again. Those changes are expected consequences of using a different route, not evidence that one of the original addresses was fake.
What an IP address does not tell you
- It does not prove the identity of the person using the connection.
- It does not provide a precise physical or GPS position.
- It does not show every device sharing a translated public address.
- It does not say whether application traffic is encrypted or safe.
- It does not remain constant across every network, reconnect, or VPN session.
If your goal is to troubleshoot, record the address together with the network type, time, IPv4 or IPv6 family, and VPN state. That small amount of context is more useful than treating an isolated value as a permanent identifier.