Every news story about online privacy includes a line about how "your IP address can be used to track you." Marketing for VPNs and privacy tools leans hard on this — the implication being that anyone who sees your IP can pull up your name, your address, and your browsing history. The reality is more boring and a lot more useful to know.
An IP address tells someone a few things. None of those things are your identity. This is what's actually on offer.
What an IP address actually identifies
An IP address is the address of a network interface, not a person. The device that made the HTTP request to load a page is sitting behind some piece of networking equipment, and that equipment has an IP. That's all the IP is — a return address for the next packet.
For a home connection, all 30 of your devices — phones, laptops, smart fridge, doorbell — share a single public IP through NAT (Network Address Translation). The destination sees one IP for the whole house. It can't tell which device made the request, or which person was holding it.
For mobile data, the situation is worse (or better, depending on your perspective). UK mobile operators use Carrier-Grade NAT, where thousands of subscribers share one public IP. From the destination's point of view, you and fifteen thousand strangers all look like the same client. This is why services that try to enforce a per-user rate limit by IP — login attempt limiters, free-tier API quotas — sometimes lock out entire mobile networks for a few minutes when one user trips the threshold.
What's roughly inferable
From an IP, the following are derivable to reasonable accuracy:
- Country. Nearly always. The regional internet registries (ARIN for North America, RIPE for Europe, APNIC for Asia-Pacific, LACNIC for Latin America, AFRINIC for Africa) publish which IP ranges they've allocated to which countries. Getting the country wrong is rare.
- ISP. Usually. The WHOIS record for an IP range names the organisation that holds the allocation — typically your ISP, sometimes a hosting company if you're on a server, sometimes a VPN provider.
- City. Sometimes. Commercial geolocation databases (MaxMind GeoIP, IP2Location, ipinfo.io) infer city from a mix of WHOIS data, traceroute patterns, and user-submitted corrections. They're right roughly 60-70% of the time at city level, occasionally very wrong — the database might place you in the city where your ISP's regional centre lives.
- Time zone and autonomous system number. Trivially derived from the above. ASN is useful for blocking traffic from known VPN providers if a service wants to.
What is NOT inferable
None of the following can be derived from an IP address alone:
- Your name.
- Your street address.
- Your browsing history on other sites.
- Your account at any service.
- Which other devices are on your network.
- What you were doing five minutes ago.
All of those require correlation with other logs — your ISP's customer record, a service's user database, a cookie set by an ad network. Law enforcement can subpoena an ISP to map an IP-plus-timestamp to a customer, but ordinary site operators don't have that access. The IP on its own is roughly as identifying as a postal code.
This matters because the privacy concern around IPs is real but mis-framed. The problem isn't that your IP uniquely identifies you. The problem is that your IP, combined with the cookies, the fingerprinting signals, and the cross-site tracking, is one more correlation key that ad networks use to connect your activity across domains. Hiding the IP alone doesn't fix that.
Public vs private IPs
The IP your laptop sees on its own network (192.168.1.42, 10.0.0.5, 172.16.0.20) is a private IP. These ranges — 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16, along with the IPv6 fc00::/7 equivalent — are reserved for local networks and cannot route on the public internet. Your router translates between the private IP your laptop has and the public IP your ISP gave it.
This is why a quick "what's my IP" check shows something very different from what your OS reports. Both are correct; they're answering different questions. Your OS reports the IP your machine has on its local segment; an external check reports the IP the world saw when your router talked to a remote server.
IPv6 changes this story a bit. Each device on an IPv6-enabled network gets its own globally-routable address, so there's no NAT in between. In principle that makes per-device identification easier; in practice, most operating systems implement IPv6 Privacy Extensions (RFC 8981), which rotate the interface ID periodically — your phone's IPv6 address changes every few hours, even without leaving the network.
VPNs, proxies, and what they actually hide
A VPN replaces the source IP on your traffic with the VPN exit node's IP. To the destination, your traffic looks like it came from the VPN. What this hides: your real IP and, by extension, your rough geographic location and ISP. What it doesn't hide:
- Anything in the application layer. Cookies, fingerprint, login state. A logged-in Google account is still logged in, VPN or no VPN — Google identifies you by the session cookie, not by the IP.
- The fact you're on a VPN. Most commercial VPN exit IPs are well-known and blacklisted by geographic-restriction services. Netflix has worked very hard at this; so have most banks.
- Traffic the VPN doesn't tunnel. Some VPNs only route IPv4 and leak IPv6. Others have DNS leaks where the DNS query goes to your ISP's resolver even though the rest of the traffic goes through the VPN.
The honest summary: VPNs are useful for hiding your geographic location from a website, dodging geo-restrictions, and stopping your ISP seeing what sites you visit. They are not a cloak of invisibility.
When to use the what-is-my-ip tool here
The what is my IP page is useful for a few specific things: confirming your VPN is on by checking the displayed IP matches the expected exit country, finding the public IP you need to enter into a firewall allow-list, or checking whether IPv6 is reachable from your connection. It reads the IP straight from the request your browser made, with no third-party geolocation lookup.
Related reading
If you're trying to work out whether IPv6 is reaching you, the check if IPv6 is working guide walks through the diagnosis. To look up the IP addresses behind a domain, the DNS lookup tool is the fastest route. For the rest of what a site can see about your browser — APIs, codecs, screen size, language — the browser diagnostic is the matching read.