IP Address Lookup

What it does

Enter any IPv4 or IPv6 address and this tool tells you what is publicly known about it: which country and approximate area a geolocation database places it in, which network operator announces it, and whether it is a special-purpose address that has no location at all. It is the same lookup a server administrator does when an unfamiliar address turns up in a log file.

The lookup runs against a database held on our own server. The address you type is not forwarded to a third-party API, so nobody else learns what you searched for.

How it works

An IP address is the number a network uses to route packets to a destination. IPv4 writes it as four decimal octets separated by dots, such as 203.0.113.5 — each octet is one byte, so no part may exceed 255. That gives roughly 4.3 billion addresses in total, and they ran out: the central pool was exhausted in 2011 and the regional registries have been rationing what remains ever since. Two things filled the gap. IPv6 uses 128 bits, written as eight groups of four hexadecimal digits, with one run of zero groups collapsible to :: — so 2001:0db8:0000:0000:0000:0000:0000:0001 is normally written 2001:db8::1. And carrier-grade NAT lets an ISP put many customers behind a single public IPv4 address.

Geolocation is a lookup, not a measurement

This is the part most sites gloss over. Nothing in a packet carries a location. Finding out where an address "is" means consulting a table someone else compiled, and that table is built from inference.

The chain starts with the five Regional Internet Registries, which allocate address blocks to organisations: RIPE NCC for Europe and the Middle East, ARIN for North America, APNIC for Asia-Pacific, LACNIC for Latin America and AFRINIC for Africa. Registry records tell you which organisation holds a block and where that organisation is registered — which is often a head office, not where the addresses are actually used. Commercial providers such as MaxMind then refine this with routing announcements, ISP-published assignment data, latency measurements and various forms of inference, down to a city-level guess.

The result is a best estimate with real error bars. Country is usually right. City is frequently wrong, sometimes by hundreds of kilometres, and for anycast or satellite addresses even the country can be wrong — the same address may be announced from dozens of cities simultaneously, so no single answer is correct. Where our database supplies an accuracy radius, the tool shows it, because a coordinate with a 500 km radius is a very different claim from one with a 5 km radius.

There is a well-documented failure mode worth knowing about. When a database can only determine the country and not the city, it may still return coordinates — historically, the geographic centre of that country. Every address it cannot place more precisely then resolves to the same point on the map. Because a great many lookups fall back to that default, the property that happens to sit at those coordinates gets treated by the internet at large as the origin of enormous volumes of fraud, spam and abuse. In the United States this caused years of harassment for the residents of a rural property near the country's centroid, and the provider eventually changed its default coordinates to points in bodies of water to break the association. The lesson generalises: a coordinate returned by a geolocation database is not evidence that anyone is at that coordinate.

The ASN is the reliable field

An Autonomous System is a network that announces its own routes to the rest of the internet using BGP — an ISP, a hosting company, a university, a large enterprise. Each is identified by an Autonomous System Number, for example AS15169 (Google) or AS13335 (Cloudflare). Unlike city-level geolocation, the ASN and operator name come from routing data that the network itself publishes to make traffic flow. If it were wrong, the network would break. That makes the operator field the most trustworthy thing on the page: it will tell you reliably whether an address belongs to a UK consumer ISP, a mobile carrier, or a cloud host — which is often the question you actually wanted answered.

Addresses with no geography

Before touching any database, the tool checks the address against the IANA special-purpose registries. These blocks have a meaning that is a property of the address itself and not of anyone's dataset, so they need no lookup and can never go stale. A private or loopback address has no location by definition — it means something different on every network it appears on — so the tool says so rather than reporting a misleading near-miss from an adjacent range.

The three that matter most in everyday use are RFC 1918 private space (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) — the addresses your own devices use behind a router; RFC 6598 shared address space (100.64.0.0/10) — carrier-grade NAT, which looks public but is not; and loopback (127.0.0.0/8 and ::1), the machine talking to itself.

Worked example

Enter 127.0.0.1 and the tool answers without consulting the database at all. It matches 127.0.0.0/8, so it is classified as loopback: localhost. Has no geography and never will — the classifier answers without touching the database. Because the classification is a fact about the address rather than a database entry, this result is identical on every server in the world and will not change with a database refresh.

Contrast that with an ordinary routable address such as 8.8.8.8. The classifier declines to classify it and defers to the database, which reports AS15169 and Google as the operator. The ASN is stable — it has been Google's for well over a decade — while the city and coordinates are an estimate that can shift between database releases.

Common uses

• Reading server logs: working out whether a burst of requests came from a residential ISP, a datacentre, or a known crawler. The ASN answers this; the city usually does not matter.
• Fraud and abuse triage: checking whether a sign-up or payment came from the country a customer claims, and whether the address belongs to a hosting provider — often more informative than the geography itself.
• Diagnosing your own network: confirming whether an address is private, CGNAT or genuinely public, which determines whether inbound connections and port forwarding can work at all.
• Checking a VPN or proxy: verifying that traffic is leaving via the exit node you expect, in the country you expect.
• Content and compliance questions: understanding why a service thinks you are in the wrong country, which is nearly always a database error rather than anything you have done.

Frequently asked

How accurate is IP geolocation?

Country is usually correct. City is much weaker — commonly wrong, and wrong by a long way on mobile connections, business circuits and any network behind carrier-grade NAT, where one public address may serve an entire region. Coordinates should be read as "somewhere within this radius", never as an address. Anycast addresses have no single true location at all. If a decision matters, use the ASN and the country; treat the city as a hint.

Can an IP address identify a person?

Not on its own. It identifies a connection at a point in time, and that connection is usually shared — by everyone in a household, everyone on an office network, or thousands of customers behind CGNAT. What it does do is give the ISP a starting point: the ISP holds the records that link an address and timestamp to a subscriber account, and can be compelled to produce them. That is also why, under UK GDPR, an IP address is treated as personal data — the Information Commissioner's Office is the UK authority on what that means for anyone storing them.

Why does my IP show the wrong city?

Usually because the database has no city-level data for your block and falls back to something coarser: your ISP's registered address, the nearest exchange or datacentre it does know about, or a regional default. Mobile connections are the worst case — traffic is often broken out through a gateway hundreds of kilometres from the mast you are connected to. Nothing is broken on your end and there is no setting to correct it; the fix is for the database provider to publish better data.

What is an ASN?

An Autonomous System Number identifies a network that announces its own routes over BGP. It is how the internet knows which operator is responsible for a block of addresses. Because it comes from live routing rather than inference, it is the most dependable field in any IP lookup — if you only trust one line of the result, trust that one.

Is looking up an IP address legal?

Yes. Address allocations, routing announcements and ASN records are published deliberately so the internet can function, and reading them is no different from reading a phone book. What is regulated is what you then do with the information: if you store visitors' addresses, UK GDPR applies because they count as personal data, so you need a lawful basis, a retention period and an entry in your privacy notice.

What is CGNAT and why do I share an IP address?

Carrier-grade NAT is how ISPs cope with the IPv4 shortage. Rather than giving each customer a public address, the ISP assigns addresses from the shared 100.64.0.0/10 range and translates many customers onto one public address at its own border. Nearly all UK mobile data works this way, and some fixed-line broadband does too. The consequences: your apparent location is the ISP's gateway rather than your area, inbound connections and port forwarding do not work without a workaround, and you can be blocked by a site because of what a stranger sharing your address did.

What is IPv6 and do I need it?

IPv6 is the replacement addressing scheme, with 128-bit addresses instead of 32-bit — enough that every device can have a genuine public address and NAT becomes unnecessary. You do not need to do anything: if your ISP and router support it, your devices already use it, and most connections now silently prefer IPv6 where both are available. It is why an address you see may look like 2a00:… rather than four numbers.

Where does the data come from?

Geolocation and ASN data come from the MaxMind GeoLite2 databases, which we build into a local database and query on our own server. The special-purpose classification comes from the IANA registries and is implemented directly, so it works even when no geolocation database is present. This product includes GeoLite2 data created by MaxMind, available from https://www.maxmind.com.

See how we build and verify our tools. To find the address you are currently connecting from, use what is my IP.