My American SIM IP Shows Another City: A Simple Explanation

Many of our customers are in China, Vietnam and other countries far from America. They buy a line in one US city, test it with a lookup website, and see a different city. Or they see only a state name. Then they write to support, worried that something is wrong. This page explains the reason in simple words. In short: the SIM really is in the city you chose, but lookup websites do not measure where a SIM is. They guess from network records, and those records follow the carrier's network, not our building. Below we explain how the guess works, show a real example from our hardware, list the other things websites check besides the IP, and tell you what to do if the result does not fit your work.

Where is the SIM, and where does the website think you are?

The SIM card sits inside a modem in our rack, in the US city you picked. That modem connects to cell towers near the rack, like any phone in that city.

But the website on the other end never sees the tower. Your traffic travels inside the carrier network to a big regional center, called a gateway. At the gateway it goes out to the internet. Many real phones in the region go out through the same gateway and share the same group of public addresses. This sharing is called carrier-grade NAT. So the address a website sees belongs to the gateway, and the city a website shows is the gateway's area. Usually that is the same metro as our rack. Sometimes it is only the state. Sometimes it is a bigger city nearby, where the carrier keeps a hub.

How a lookup website finds a city

An IP address is only a number. It has no GPS inside. Lookup websites buy their answers from location databases. The well-known ones are ipinfo, MaxMind GeoIP2, DB-IP and IP2Location.

Each database collects clues. The carrier registers each block of addresses with an office address. Internet routing shows where a block is announced. Some networks publish a small file, called a geofeed (standard RFC 8805), that says which region each block is for. Databases also test response times and collect location reports from apps. Then each database makes its own best guess.

Because the clues point to the gateway, the guess stops at the city or state level. It never shows a street, a zip code or a part of town. If a seller promises you a mobile IP that shows an exact street, do not believe it.

A real example: Boston

We keep Verizon and AT&T modems together at our site in Boston. Same building, same shelf, same towers. When we look up the Verizon addresses, the databases say Boston. When we look up the AT&T addresses, the databases say New York.

Why? AT&T collects much of its mobile traffic in a few big hub cities. Because of that, an AT&T address often shows a larger city than the place where the SIM really is. For this area, that bigger city is New York. Verizon's network sends Boston traffic out in a way the databases connect to Boston. So the carrier you choose can change the city you see, even in one building.

Why two lookup websites give two answers

Each database uses its own clues and updates on its own schedule. Carriers also move blocks of addresses from one market to another. So one website may say the city, a second may say only the state, and a third may say a nearby city.

Your result can also change when you rotate to a new IP, or when a database is refreshed. The modem stays where it is the whole time. In smaller markets a carrier sometimes serves several states with one pool, so a new address can even show a neighbouring state. This is normal. Real phones in that city get the same results, and people keep using TikTok, Instagram and other apps on them every day. Platforms accept a mobile IP that moves around inside one carrier network, because a person who flies to another state looks the same way.

Important for buyers abroad: your browser also gives a location

Websites do not look only at the IP. They also read your browser. This part matters most for customers outside America.

Your computer clock may be set to Beijing or Hanoi time. Your browser language may be Chinese or Vietnamese. The HTML5 location feature in the browser asks your device for its position, using GPS or nearby Wi-Fi, and it ignores the proxy. WebRTC can show your real local address if it is not blocked. If a website sees an American carrier IP but an Asian timezone, that does not match, and the website may become careful.

The fix is an antidetect browser. In GoLogin or Undetectable.io, set the profile to take its timezone and location from the proxy. Then the clock, the location and the IP all say America. One more rule: do not open the same account from two different places at the same time. That is what platforms flag, not a normal IP change.

What to do, step by step

Follow these steps after you buy a line.

• Ask yourself what your work needs. Do you need one exact US city, or is any address in the right state or anywhere in America enough?
• Test your IP with the free checker on our Tools page. Then test it on ipinfo.io, and on browserleaks.com/ip, which shows several databases in one place.
• Look at which city most answers show. Trust the majority, not one website.
• If the city does not fit your work, write to support. Changing to another city or another carrier is free. You can move the location yourself in the dashboard, or we can choose the carrier that shows the city you need.

Frequently asked