What does your IP address actually reveal, and what does it not? IPv4 versus IPv6, the private addresses behind your router, how to find your own, and what websites see when you use a VPN or a proxy, with real examples.
An IP address is the numeric address assigned to every device on the internet or on a local network, and it is what lets data find its way to the right place, much like a postal address for packets. Two versions are in use: IPv4, written as four numbers such as 203.0.113.42, and IPv6, written as groups of hexadecimal digits such as 2001:db8::1. At home, each device has a private address behind the router and shares one public address on the way out. The quickest way to see your public one is the what's my IP tool, which shows the address the server sees your request coming from.
That tool reports only what actually reaches the server: the IP, your browser's user agent, the language header and, if your request passed through a proxy that added one, the X-Forwarded-For value. It does not guess your location or your provider. To see where a short link leads without connecting to it yourself, use the redirect checker; for a strong router admin password, the password generator; to write IPv6 addresses correctly inside links, the URL encoder; and to read the JSON that IP lookup services return, the JSON formatter.
Everything that travels across the internet is split into small packets, and every packet carries two addresses in its header: where it came from and where it is going. Routers along the path look only at the destination to pass the packet to the next hop, and the reply finds its way back thanks to the source. Without an address there is no conversation. Note that an address describes a device's position on a network more than its identity: the same laptop goes online from three different addresses at home, at work and in a café.
People like names; machines like numbers. When you type a site name into the browser, the Domain Name System (DNS) is asked first and returns the numeric address behind that name, and the connection is made to that number. One domain can point to several servers and to both IPv4 and IPv6 addresses. Knowing this split helps when a site will not load: the fault may lie in name resolution rather than in the server itself.
Most home and mobile connections get a dynamic address: the provider leases it for a period, and it may change when the router restarts or the lease expires. On mobile data it changes even more often. Servers, CCTV recorders and anything reached remotely usually rely on a static address that does not change, which most providers offer as a separate option.
IPv4 addresses are 32 bits long and written as four decimal numbers from 0 to 255 separated by dots. That allows about 4.3 billion addresses in total, which the growth of the internet outran: IANA handed out its last unallocated blocks in 2011. IPv6 solves the shortage with 128-bit addresses written as eight groups of hexadecimal digits separated by colons. One run of consecutive zero groups may be collapsed into ::, so 2001:0db8:0000:0000:0000:0000:0000:0001 becomes simply 2001:db8::1.
| Property | IPv4 | IPv6 |
|---|---|---|
| Length | 32 bits | 128 bits |
| Notation | Four dotted decimal numbers | Eight colon-separated hex groups |
| Example | 198.51.100.7 | 2001:db8:85a3::8a2e:370:7334 |
| Total addresses | About 4.3 billion | About 3.4 × 10^38 |
| Sharing addresses | Very common via NAT | Every device can have a public one |
| Longest text form | 15 characters | 39 characters (45 with an embedded IPv4) |
The example addresses in this article were chosen on purpose. The blocks 192.0.2.0/24, 198.51.100.0/24 and 203.0.113.0/24, along with the prefix 2001:db8::/32, are reserved for documentation by RFC 5737 and RFC 3849, so they never belong to a real device.
The colons in an IPv6 address clash with the colon that introduces a port number, so when an IPv6 literal appears in a link it goes inside square brackets: [2001:db8::1]:8080. Link-local addresses on a LAN also carry a zone identifier naming the network interface, as in fe80::1%eth0. Inside a link, that percent sign must itself be encoded as %25 (RFC 6874), a job the URL encoder handles for you.
A public address is unique on the internet and is the one websites see. Private addresses are valid only inside a local network, which is why millions of homes can use 192.168.1.10 at the same moment: those addresses never leave the building.
| Range | Type | Where you will see it |
|---|---|---|
| 10.0.0.0/8 | Private (RFC 1918) | Office networks, some routers |
| 172.16.0.0/12 | Private (RFC 1918) | Corporate networks, virtual machines |
| 192.168.0.0/16 | Private (RFC 1918) | Most home routers |
| 100.64.0.0/10 | Shared space (RFC 6598) | A provider's carrier-grade NAT |
| 169.254.0.0/16 | Link-local | What Windows assigns itself when DHCP does not answer |
| 127.0.0.0/8 and ::1 | Loopback | The device itself (localhost) |
| fc00::/7 and fe80::/10 | IPv6 local addresses | Traffic that stays on the LAN |
Your phone, TV and computer all go online through the same public address. The router rewrites every outgoing connection to use its own public address and keeps a table of which device is waiting for which reply. That process is called NAT. Its side effect: a connection started from outside cannot reach a device inside unless you set up port forwarding on the router.
If the WAN address on your router's status page falls between 100.64.0.0 and 100.127.255.255, or simply differs from the public address our IP checker reports, your provider has placed you behind carrier-grade NAT, where several customers share one public address. Everyday browsing is unaffected, but port forwarding stops working, and reaching a home camera or game server from outside becomes difficult. If you need that, ask your provider for a public or static address.
Local settings cannot tell you the address websites see; you need a server looking from the outside. Open the IP checker and it shows the address the request arrived from. Depending on your network and how the connection was made, that may be IPv4 or IPv6, and both are normal.
ipconfig. The “IPv4 Address” line is the device's local address, and “Default Gateway” is your router, usually 192.168.1.1 or 192.168.0.1.ipconfig getifaddr en0 in Terminal.ip addr in a terminal lists the addresses of every interface.Every site you visit sees the address your connection comes from; that is simply how the conversation works. What can be inferred from that single fact is more limited than many people assume.
| Can be inferred | Cannot be inferred |
|---|---|
| The public address of the connection | Your name or ID number |
| A rough region (a geolocation database guess, often city-level and sometimes wrong) | Your street address |
| Which provider or organisation the address is registered to | Your browsing history on other sites |
| Whether it belongs to a VPN or a data center | The files and passwords on your device |
The link between an address and a subscriber exists only in the provider's records and is normally disclosed only through a legal process. Your browser, however, sends other details with every request: a user agent describing the browser and operating system, an Accept-Language header listing your preferred languages, and any cookies you received earlier. What identifies you is usually not the address but these signals and the accounts you are signed in to.
A location is a guess made by looking the address up in a database, and on mobile connections it can be off by hundreds of kilometres. The tool therefore deliberately shows only what the server genuinely sees: the address, the user agent, the language header and, when present, X-Forwarded-For. Everything on the screen is a verifiable fact rather than an estimate.
Your connection most likely uses dynamic addressing. A router restart, an expired lease or switching cell towers on mobile data can all assign a new one. IPv6 devices also generate temporary privacy addresses and rotate them regularly, which is expected behavior.
The address alone gives no access to your device. The real risks are open ports, outdated router firmware and the router's default password. Close those and a known address is a small risk in practice; if your connection is ever targeted, restarting the router on a dynamic plan usually gets you a fresh address.
It is the most common local management address for home routers, and it sits in a private range, so it cannot be reached from the internet. Typing it into a browser opens the router's admin page. On first login, replace the default password with a long random one.
In its 2016 Breyer judgment, the Court of Justice of the European Union held that even dynamic addresses can be personal data under certain conditions, and privacy regulators in many countries take a similar view. That is why websites describe how they log addresses in their privacy policies.
Related reading: why a database column for IPv6 addresses needs at least 45 characters is covered in the character limits guide; generating strong passwords for your router and accounts in strong passwords and secure identifiers; and how redirects route a request in 301 vs 302 redirects.
