Updated

Smartphone reviews often ignore an increasingly important feature: the ability to switch from one cellular carrier to another.

Here's why that capability matters.

The decline of long-term cellular contracts, together with intense price competition, means that consumers can really shop around, switching cellular providers when they find a better deal.

Secondly, there's little reason these days to buy a new phone when you make that switch. Phones aren't improving as fast as they used to—today's models are only moderately better than two-year-old phones when it comes to cameras and displays. And many phones are tougher, too. So an unlocked phone you buy today can easily last three years or longer.

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But U.S. consumers can only bring a phone to a new carrier if it can work with both network technologies used in the country. These are the CDMA system used by Verizon and Sprint, and the GSM system used by AT&T, T-Mobile, and a number of cell providers that piggyback on their networks.

Manufacturers don't generally tout this feature, but several popular phones allow you to move easily from carrier to carrier by swapping out the SIM card, an easy operation. These "unlocked," network-neutral phones also make it easier to travel internationally.

The smartphones below, which are arranged alphabetically, all did well in our ratings. Some of them have been on the market for a while and may not be readily available at carrier stores, but you can find them at other retailers. (You can also check out our advice on how to buy a used smartphone.)

This list doesn't include every option out there. You can check out the network compability of any phone using a nifty web tool called willmyphonework. You’ll need to enter information including the model number and the provider you plan to use. The site will tell you whether the phone will work and also whether it will be able to access the that provider's fastest 4G network—with some combinations of phone and network, you'll only get 3G speeds.

Apple iPhone 7

Both the iPhone 7 and iPhone 7 Plus are network-neutral, with one big cautionary note. When it comes to compatibility across networks, not all iPhones are created equal.

The iPhone models sold for Verizon and Sprint service (iPhone Model A1660 and iPhone Plus A1661) have the hardware needed to work with both GSM- and CDMA-based networks, but the reverse isn't true. Phones sold for AT&T and T-Mobile service work only on GSM-based networks. That restricts your options for switching carriers in the future.

In other respects, the Apple iPhone 7 and 7 Plus are high-class phones, edging out their predecessors, the 6s and 6s Plus in several respects. (Those phones are also network-neutral; see below.) The newer iPhones have a water-resistant case and an optical image stabilizer. The main 12.2-megapixel camera does a great job, and this generation of iPhone has a second rear camera that gives you 2X telephoto zoom.

The main caveat with the iPhone 7 models is that they lack a standard 3.5mm headset jack. The phone's ear pods (included) are designed to plug into the phone's Lightning port, which also handles charging and data syncs. You can use headphones with 3.5mm jacks by plugging them into a Lightning adapter that comes with the phones.

Apple iPhone 6s

As with the iPhone 7, if you want a truly unlocked iPhone 6s or iPhone 6s Plus, you'll need to get a Verizon or Sprint-compatible phone. These will also work on a GSM network. The AT&T/Sprint GSM phones aren't equally versatile—they can't be used on CDMA networks.

Featurewise, you can think of the iPhone 6s and iPhone 6s Plus as a cheaper, non-water-resistant version of the iPhone 7. The 12.2-megapixel main cameras are still among the best we've seen, and you'll also get top-notch battery performance—at least when compared to earlier iPhones.

You also get two things some people lament losing with the iPhone 7 model: The 3.5mm headphone jack, and a real Touch ID/Home button that reacts when you press it, even with gloves on. (On iPhone 7 models, the Touch ID/Home button is part of the touchpad, and it sometimes ignores gloved hands.)

Apple iPhone SE

Starting at $400, the iPhone SE is the cheapest phone Apple makes. As with the iPhone 7 and 6S, you need to get the Verizon or Sprint models if you care about network versatility. Those phones work on both CDMA and GSM networks. The AT&T and T-Mobile models work only on GSM networks.

The SE allows users on a budget to enjoy the benefits of the Apple ecosystem, including mobile payments via NFC and Touch ID authorization.

Its price tag may sound a little high for something we're calling a cheap smartphone, but that's Apple for you. Note, too, that the 4-inch display can seem puny in a world dominated by smartphones with displays larger than 5 inches. (However, to some small-is-beautiful consumers, the SE will seem just right.)

Google Pixel

If you’re looking for an unlocked smartphone that can combine Google’s artificial intelligence with great hardware and the ability to work on both GSM and CDMA networks, look no further than the Pixel and Pixel XL, the first Google-branded phones.

Google Assistant—the phones' built-in, Siri-like voice-activated search tool—tailors its responses according to your location, the apps you have open, and even the messages you have sent and received.

The 12.3-megapixel rear-facing camera produces some of the best still and video images we’ve seen.

The smaller Pixel features a 5-inch display while the XL offers a 5.5-inch quad HD display and a bigger battery that provides more than 32 hours of uninterrupted talk time.

And there's one advantage to the Pixel phones over other Android models: These phones are first in line for security patches, home automation, and other futuristic updates.

Motorola G4 Plus

That's a Moto G4 Plus pictured above, but Motorola actually gives you a few choices, all of them relatively inexpensive.The Moto G4 Plus, Motorola Droid Turbo 2, and Moto X Pure can all work on both GSM and CDMA networks.

These phones are also notable for their touch-free controls. For instance, chopping the phone downward twice turns on the LED flashlight. If the phone starts ringing while you’re in a meeting, picking it up switches it to vibrate mode. And if you don’t want to be disturbed, you can put the phone on the table face-down to silence calls and notifications.

The Turbo 2 and Moto X Pure have 5.4-inch and 5.7-inch displays, respectively, that present photos, videos, Web pages, and other objects with more than 500 pixels per inch of detail.

The Turbo 2’s shatterproof display is warranted against cracking for four years. The HD resolution of the Moto G4 Plus’s 5.4-inch display is just 1080P, not remarkable by today's standards but plenty good enough for most users. And it only costs between $150 and $300.

All of these Motos feature capacious batteries that can crank continuously for a full day of mixed use.

Samsung Galaxy S6 edge

Samsung loyalists will need to find a previous generation phone if they want to switch between CDMA and GSM networks.

Although it's been on the market for two years, the Galaxy G6 is brimming with features that will satisfy most smartphone users for the foreseeable future. The highlights include a long-lasting battery that can be rapidly and wirelessly recharged, and a top-notch camera with an optical image stabilizer.

The Galaxy s6 Edge features a curved Quad HD display that's both cool and practical. For instance, you can pull up your most important contacts, apps, and news sources with a sweep of your finger from either side of the display.

Not into curved screens? Take a look at the phone's sibling, the Samsung Galaxy S6, which is nearly identical except for its flat screen.

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