Everyone knows the names of the main carriers in the US—AT&T, T-Mobile, and Verizon—but many others are floating around as well. Google Fi Wireless is one of the more popular alternatives to the Big Three, but you may be wondering how it actually works. We’ll spill Google’s secrets.

What is Google Fi?

If you’re wondering which network Google Fi uses, you probably already know it isn’t your typical cell phone carrier. It’s what’s called a “mobile virtual network operator,” or MVNO for short. Think of it as a cell phone company that’s renting space on the networks of bigger carriers like Verizon and AT&T. This is a great deal for everyone involved: the big carriers get extra money, and Google Fi can offer service without the hassle of building its own towers. Other popular MVNOs in the U.S. include Mint Mobile, Tello, Ting, and Visible.

What Network Does Google Fi Use?

Google Fi has actually used several network providers over the years. It started out in 2015 as “Project Fi” and used three different carriers: T-Mobile, Sprint, and U.S. Cellular. The headlining feature was the ability to switch between these carriers to find the best signal. But this only worked on a few phones. Later, Fi worked on more phones, and when T-Mobile bought Sprint, this switching feature wasn’t as important anymore.

Now, Google Fi only uses T-Mobile’s network (U.S. Cellular stopped working with them in 2023). So, you’ll have good coverage where T-Mobile is strong. This is great because T-Mobile has one of the best networks in the U.S., which is why many other MVNOs use it as well. Google Fi customers can get 5G in different kinds: mmWave, Low Band, and Mid-Band.

What About Roaming?

One of the shortcomings of MVNOs is coverage while roaming outside of your country. Google Fi roaming is (mostly) easy. When you travel outside the US, Canada, and Mexico, your phone will automatically connect to a compatible network. You can talk, text, and use data just like you do at home. There are no complicated settings or manual switches needed.

If you have Google Fi’s “Flexible” or “Unlimited Plus” plans, data rates are exactly the same home and away. Texts are also still free, but calls are $0.20 per minute. Google Fi’s third plan, “Simply Unlimited,” does not include international calls, texts, or data. Check out our full explainer on Google Fi for more information about plans.

Since Google Fi uses T-Mobile’s network, you’ll get good coverage in many places. You have the option to only pay for the data you use, which is great if you don’t need a lot. If you like having control over your phone plan and you live in an area with good T-Mobile coverage, Google Fi is a nice option.