Samsung Galaxy S8

Best answer: If you didn't buy a phone that was advertised as unlocked the best way to make sure is to try a SIM card from a different carrier. If you don't have access to one, you can likely turn to the carrier you're expecting to switch to in order to try.

Why buy unlocked?

You've probably heard a lot of talk about using MVNO carriers as a way to find a cheaper alternative for service. It's something that's gaining popularity and while it isn't exactly mainstream just yet, it's getting there. We think that's great because having even more choices can't be a bad thing. And even if you go with one of the "big" carriers, having the ability to switch whenever you want puts the power in your hands.

But no matter which carrier you want to switch to, you'll need to make sure you have a SIM-unlocked phone. That means you can use a SIM card from any company and as long as the hardware is compatible with the network, it just works.

While some of us already know if our phones are unlocked or how to check, here's what you need to know if you are looking for a little help.

Where did you buy it, and how?

In the U.S., Verizon is the only carrier that sells nearly all of its smartphones unlocked. What we mean here is that if you walk into a Verizon store or use its website and buy a phone made for Verizon with the branding on it, it's probably going to be SIM unlocked anyway. Note that this doesn't mean you should buy a Verizon branded phone to use on a different network, because SIM unlocked doesn't mean fully compatible. We just mean that Verizon is okay with you putting another SIM in the phone and letting the hardware try to connect to a different network.

The other three networks, as well as Best Buy or other third-party carrier resellers that sell devices with financing plans on behalf of carriers, are not as reliable when it comes to selling unlocked phones. Some phones are, some aren't — but every one of them can be unlocked, because that's the law.

If you bought your phone from Amazon, B&H or another online retailer, the listing has information on if it was unlocked. If you don't remember, a quick revisit of the listing will let you double check. Of course, if you bought your phone directly from the manufacturer and if it was listed as unlocked, it will be. All phones sold directly from Google are unlocked, and many phones from other manufacturers like Samsung and Motorola are sold directly and SIM unlocked, too.

For the rest of the phones out there, there's really only one fool-proof way to check: try it.

Use a SIM card from a different carrier

You'll see websites that claim you can check if your phone is unlocked online. While that might be true, these services cost money and are often incorrect. I'll come right out and say it: don't bother.

Instead, you can call your carrier or the carrier or MVNO you're thinking of switching to. Companies keep a database of IMEI numbers that says which phones are compatible, unlocked, or blacklisted. You might not have any luck here, though, because the person answering the phone might not be able to give you that information — they either don't have access to it or they aren't allowed to tell you over the phone. It's worth a try if you don't have access to a SIM card from a different company, though.

Skipping all of that, the easiest way to find out if your phone is unlocked is to just put in a SIM card from another carrier. And it doesn't have to be a SIM card connected to an active account — the phone will try to initiate a connection with any SIM card in place. The process is as follows:

  1. Make a phone call using your current SIM card, if possible. This is to check that the phone is working properly. (Call your mom and tell her hello; she'll appreciate it.)
  2. Shut off the phone and remove the SIM card. Look in the manual or online if you're not sure how to do this, and if you need a SIM card removal tool, a paperclip usually works fine.
  3. Put the new SIM card in your phone and power it back on.
  4. If you're greeted with a dialog box telling you to enter a SIM unlock code, your phone is SIM locked to the carrier it was originally purchased from.
  5. If you don't see an unlock code prompt, check that it says you have service if you used a valid SIM card. If you do, your phone is probably unlocked. Try making another phone call. (Mom won't mind two calls on the same day.)

If you can't call using the new SIM card, you'll probably get a recorded message with some error code. You can jot down the code and check online to see why the call can't be completed so you know if it's because of a SIM lock or because of incompatible hardware. Having a phone that is wholly incompatible with another network is unlikely nowadays, but it's worth checking.

If you don't have access to another SIM card, you can also take your phone into a carrier store and tell them you're thinking of switching carriers and want to check if it's unlocked. Don't feel bad about telling a little white lie to a carrier — they tell them to us all of the time. They should be able to help you put in a SIM card and check.

If your phone is SIM-locked, don't fret. Carriers are required to SIM unlock your phone provided it has been paid for in full and your account is in good standing. Each carrier has slightly different rules in terms of how long you have to own the phone and how long your account has to be open for, but you can give customer service a call and they'll help you out. Here's some information for the major U.S. carriers:

When you don't need a SIM-unlocked phone

At the top of this article, we said in most cases you do need a SIM-unlocked phone to try another carrier. That's true, but there is one popular use-case where it doesn't matter: using a carrier-branded phone on that carrier's own MVNO. T-Mobile, Verizon, Sprint and AT&T all operate their own MVNOs or self-branded prepaid services, and those SIM cards will work in the "locked" phones of the same carrier — at least, provided the carrier doesn't explicitly block those devices.

Be sure to check compatibility before making the switch, but know that you don't have to have an explicitly unlocked phone in order to use their lower-cost options.

Our pick

Samsung Galaxy S10+

The best Android phone today is also available unlocked.

Samsung has pared back all of its carrier-specific models and now offers a single unlocked version for the entire U.S. You can buy this fantastic Galaxy S10+ and use it on any carrier you choose — and it'll even work internationally.

Unlocked for less

Google Pixel 3a

A great unlocked phone with an exceptional camera for less money.

The Pixel 3a takes much of what makes the Pixel 3 great and wraps it in plastic for a much more affordable package. The camera is fantastic, and everything else gets the job done for the price. And it's only available unlocked.

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