Will that unlocked phone work with your wireless carrier? Here’s how to tell

The days of immediately signing up for a new device when your phone contract is up are over. These days, a decent smartphone can see more than a couple of summers, so why upgrade when there’s life in the old dog yet? Switching to a new carrier with your existing phone is an excellent way to save money, and thanks to phone unlocking, easier than ever.

But, as much as we hate to be the bearers of bad news, there may be reasons you can’t move to a specific carrier — and those reasons may be your smartphone’s bands. While many smartphones are capable of working on most smartphone bandwidths available in the U.S., there are some that cannot, and the last thing you want to do is lock into a new contract and then find out your phone is incompatible with the carrier’s choice of bands.

Figuring out whether an off-contract phone is compatible with your network doesn’t have to be intimidating, however. This guide will be able to tell you all you need to know.

What are smartphone bands?

First off, it’s important to know what bands are. Smartphone “bands” — short for bandwidth — are the frequencies your carrier uses to communicate with your phone. Your phone needs to be able to communicate with your carrier in order for your phone’s basic functions to work. Think of it like walkie-talkie channels: If your carrier is using channel four, but your phone can only access channels one to three, well, you’re not going to get very far. Smartphone bands work the same way, and they govern your phone signal for texts and calls, your 4G connection, and even your 5G connection — if you’re lucky enough to have access to 5G.

GSM and CDMA

Just to make things slightly more confusing, the U.S. also has access to two different network standards, with each carrier using one, but not the other. The first, GSM, stands for “Global System for Mobiles” and is used primarily by T-Mobile and AT&T. It’s also the more popular network standard internationally, which may be something to keep in mind if you’re planning on venturing outside the U.S. with your cell phone.

CDMA (Code Division Multiple Access) is used by Sprint, Verizon, and U.S. Cellular, and outside of the U.S., it’s far less common than GSM. But that doesn’t matter much inside the U.S. when the big carriers are split between GSM and CDMA. However, with T-Mobile’s acquisition of Sprint, that carrier’s CDMA network is currently being decommissioned, and bands are either being sold off or transferred to T-Mobile.

So this is all very informative, but what does it mean for you? Well, GSM and CDM don’t play well together. In fact, they don’t play at all. If your phone is set to work on GSM, it won’t work with CDMA, and vice versa. Thankfully, most phones work with both when unlocked, but some notable brands only work with GSM — so it’s important you know which your phone works with.

What is an unlocked phone?

In the simplest of terms, an “unlocked” phone is a phone that’s compatible with one or more cellular networks.

You may have bought an unlocked phone directly from the manufacturer or retailer, or you may have unlocked a phone that was previously locked to a single carrier. This is usually done at the end of a contract, and it’s completely legal to do. We have a full guide on unlocking your phone if you need a hand with that.

The benefits of an unlocked phone are pretty clear — you can use it on any carrier you want. However, don’t make the mistake of thinking that this means bands don’t matter. The bands your phone can access are determined by its hardware, and all unlocking does is allow your phone to do something it was held back from doing through locking.

How to check if your phone is compatible

All right, time to get down to brass tacks: How do you find out what your phone is capable of? Well, the easiest way is to use an online database like WillMyPhoneWork to look up your phone and intended carrier to see whether they’ll play nice. However, that tool has its limits, and you may find the latest phones and those with 5G compatability missing. We’re sure those devices will be added eventually, but in the meantime, there are other ways to figure out which bands your phone has.

There are a few things you’ll need to know. First is, of course, your phone’s model. Depending on the phone, it may also be worth knowing your phone’s model number. You can find that by going to your Settings, then hitting About Phone. You can then usually find the information you need next to Model Number.

Then, head over to a website like GSMArena. From there, search for your phone and access GSMArena’s entry for your phone. If your phone has different configurations for different model numbers, then you’ll be able to select individual model numbers above the spec sheet. Select your model, if required, then open the drop-down list for Technology under Network. This will list all your phone’s network bands. After that, it’s simply a case of cross-referencing with the network bands your chosen carrier provides.

Here’s the list of 3G bands offered by the four major carriers in the U.S.:

Here’s a chart that includes the 4G bands and frequencies of all four major U.S. carriers:

Note: Bolded bands in the 4G LTE Bands section are the carrier’s main bands, and your phone will need to be compatible with at least one of these bands to be compatible with the network.

Finally, if you’re lucky enough to have access to 5G in your area and have a 5G-capable phone, here’s the technology your phone will need to access each carrier’s 5G network.

A note on Sprint

You may have noticed that Sprint is missing from the tables above. That’s because, as a result of T-Mobile’s acquisition of the brand, Sprint’s networks are currently in the process of being decommissioned, and the band access will either be sold to other brands or folded into T-Mobile’s coverage. We have included those bands moving to T-Mobile in the tables above.

Sprint’s use of CDMA will also be shut down, so Verizon or U.S. Cellular will be your only choices if your phone has CDMA-only access.

MVNO

If you’re someone who is currently using a mobile virtual network operator or MVNO, the means of determining your smartphone’s adaptability is the same … for the most part. Providers such as Metro PCS, Cricket, and Google Fi retail service atop larger telecoms, riding on the backs of major networks like T-Mobile and Verizon. After you recognize which network your MVNO uses to perform service, referring to that parent network’s frequencies and bands is the most dependable and safest way to conclude whether or not your unlocked handset is supported.