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What is an 'unlocked' phone? (And why do I care?)

Unlocked. It's a word you'll see used a lot on websites about mobile technology, and most people writing about it will be sure to let you know that it is a good thing™. And it is (See? told 'ya). But unlocked can mean different things — that are all good things — depending on what, exactly, we're talking about.

Maybe you're wondering about being able to unlock the bootloader on the phone you want to buy next. Or maybe you'll need to SIM unlock your phone so you can take that trip abroad and not pay AT&T ten-cents a minute and a handful of dollars each time you check your email. Both are important, and we're going to talk about the differences.

The bootloader

HTC Bootloader

To many of us, the words "unlocked bootloader" bring images of wonderful far-away lands where unicorns play Half-Life 3 and flash ROMs at night around the campfire. Or something like that — maybe that's just me. An unlockable bootloader is important to those of us who want to modify the software that came installed on our phone.

A bootloader is a program that loads an operating system when a computer is powered on. Usually, it does its thing in the background and loads things to the normal user state, but a bootloader can also bring up other interfaces, like recovery or fastboot. It's what runs first every time you turn your phone on, and is usually set up so that only "official" software can be installed and will run.

The bootloader on your phone came locked from the factory. This is a good thing, because having a bootloader that's not locked will allow modification to the software, and is not secure at all. But the ability to modify the software on our phones is precisely why many of us want an unlocked bootloader.

Here's where things get a little dicey. We've seen that most manufacturers are OK with allowing you to unlock the bootloader (using a token or key they supply) as long as you're OK with potentially voiding your warranty. This is a good thing. This is what freedom smells like and all that. Seriously, once we've paid for a phone it should be ours to break as we like.

Seriously, once we've paid for a phone it should be ours to break as we like

The people who own and operate the network that your phone runs on (this is mostly a U.S. thing) feel differently. They want to decide exactly what software is running on the phones and tablets that use their network. And that's their right. Besides potential issues custom software could create on the network itself, they have customer service and warranty concerns to manage. It's their network, and they get to try and decide (for the most part) what can be running on it. The way they (try) to make this happen is by offering their own version of a phone that can't be easily bootloader unlocked.

Remember, if your phone has a carrier name or logo printed on it, they are the ones it was built for. They sold it to you, not HTC or Samsung or Motorola or anyone else. While they may be more than happy to pass you off to the manufacturer if you have issues, it's still their product.

The easy solution to make sure you have a phone with an unlockable bootloader is to find out before you buy. Depending on the crafty guys and gals who are able to defeat encryption schemes with workarounds and find a method to unlock the bootloader on a phone that someone doesn't want you to unlock is always possible, but never certain.

For most people out there (some of us are waayyyy out there) this isn't a big issue. But it might be an issue for you.

SIM unlocked

SIm unlocked

SIM unlocking, or network unlocking, has nothing to do with a bootloader or custom ROMs. It's just a way to allow your phone to use a different network than the one whose name is on the door where you bought it. This is mostly a North America thing, where carriers sell phones that won't operate on other carrier networks.

Usually, support for other networks is built into your phone, and you can unlock the SIM to use them. You can do this a couple of different ways.

The first, and easiest, is to call the people who sold you your phone and tell them you need it SIM unlocked. They can give you a code you enter when you insert a different carrier's SIM card that will allow you to use the phone on other networks. Usually, if your account is in good standing and you have a need to get your phone SIM unlocked, they will help you out. But not always — each carrier has different qualifications for when it will give you an unlock code.

The good news is that some carriers are moving away from this practice, at least in part.

Another method is to use an unlocking service. You'll find them online, and once you tell them what model of phone you want SIM unlocked and pay them a bit of cash (usually around $20) they'll send you a code — just like the carrier would — to SIM unlock the phone. This is usually a code directly from the network provider, who sells them in bulk for folks to resell. This works great as long as you're using a trustworthy company. Use the forums to help find a trustworthy company.

Another method is via root or custom ROM. You might need an unlocked bootloader (read all that above), too. Essentially, you're installing software or modifying existing software so that the phone is SIM unlocked. This is legal, but not nearly as easy as getting a code to enter when you pop in a new SIM.

The good news is that some carriers are moving away from this practice, at least in part. Once we have nationwide, cross-carrier voice over LTE calling and CDMA networks are repurposed as pure data channels, any phone with the right radio frequency bands can run on the Verizon network. The others will follow, because commercials with lightning bolts and shiny people will tell you how great it is, and they will want to be great, too. Sprint also sells most new phones as SIM unlocked. AT&T and T-Mobile, who use SIM cards for both voice and data, still love to network lock their phones. Canadian carriers also love to lock you in.

You might never need to worry about network unlocking your phone. Once you've found a network provider that works best for you, you'll be buying phones compatible with their network, and using them on their network. Unless you're traveling outside your home country, you don't need to SIM unlock your phone. And even then, most carriers offer service while you're abroad if you're willing to pay for it. The important thing is that you understand what your options are, and how to do it if you need to do it.

Jerry Hildenbrand
Jerry Hildenbrand

Jerry is an amateur woodworker and struggling shade tree mechanic. There's nothing he can't take apart, but many things he can't reassemble. You'll find him writing and speaking his loud opinion on Android Central and occasionally on Twitter.

86 Comments
  • Sim locking a phone sadly isn't just a US thing. Operators here usually lock theirs, especially Orange, even if you buy it outright from them. Vodafone is hit and miss. Some phones are locked some are not. Telekom usually doesn't lock their phones unless its a special model made under their own branding. Posted via the Android Central App
  • Here in New Zealand only the sub $100 phones are SIM locked. It costs $30 to get it unlocked within 12 months. Posted via my Motorola Startac
  • In Canada, ALL the phones are sim locked. No exceptions. Posted via the Android Central App
  • Same in Isarel
    Carrier phones come unlocked since 2011 Posted via My G2
  • You know, just call your carrier, have then put on the Global plan and just do it that way. I don't want to worry about losing a SIM card or putting a new one on, etc. These articles always piss me off because like 80% of Americans never leave thier STATE. Posted via the Android Central App
  • Is that really something to get pissed off about?
  • +1 Posted via the Android Central App
  • I agree. Why in the world, would someone's view on this, piss him off.
  • In terms of convenience, the carrier's Global plans are hard to beat. However, there are two primary advantages, IMO to having a US phone that is sim unlocked. 1. Price and Monetary savings--prepaid and local sims normally offer more data and better calling rates for cheaper prices. 2. Peace of mind knowing that I am not on my carrier's plan and risking exorbitant charges if my phone does something unexpected or if my usage changes. When I put that prepaid sim in my phone, I knew what I was paying ahead of time and that I would be unable to go over my allowance.
  • I agree, most Americans don't travel outside the USA. I on the other had do about twice a year and having a sim unlock and whatsapp save me tons o money. I get a local sim and for two weeks unlimited data, text, phone cost me abt $12. way better than getting global data thru my USA carrier Posted via AC app on my X 14
  • They piss me off because 80% of the people here know damn well what the difference is, otherwise they wouldn't be here. Yet the bloggers insist on catering to the dumbass morons too simple minded to use google
  • New Normals are showing up on the site daily. Don't hate these articles. They're there so you don't have to deal with Newbies to Android. I praise these articles because Normals know how to use a browser and search. And the AC website is exactly that. Keep these articles coming, they help me stay sain....! Still using the Sprint GSIII on FreedomPop Unlimited for $19.99
  • +1 Posted via the Android Central App
  • too simple minded to use google? you saw this article because you frequent this site. others googled it! dummy.
  • Well, that explains it.
  • Seems like a silly thing to get upset about. It's valuable to some users like me and others who don't purely buy phones from their network provider.
    Sim locked phones matter to me, because I almost always have at least two phones, one work and one personal.
    I use AT&T for work and T-mobile for personal and I like to swap phones around, sometimes I'll buy a new personal phone and make my old personal phone my work phone or vice versa Not to mention if you don't get your phone from the carrier store, it enables you to use a AT&T phone on t-mobile or vice versa.
    There are a lot of special cases outside of the typical american who upgrades once every two years on contract and never takes out his sim card. Hell my current work sim card has probably been moved between at least 10 phones in the past 3 to 4 years.
  • It sounds like you knew everything that is written in this article before it was posted, which is lightyear's point. The readers of Android Central are already aware of this information; it doesn't have much value to the frequent readers of this site because it doesn't tell us anything new.
  • It is worth pointing out that recent Samsung phones that are "sim unlocked" may still not work with some foreign sims due to Samsung attempts to prevent even sim free/unlocked phones being used in certain countries. Many sim - free Samsung phones have a sticker on the outside of the box warning of this due to customers being somewhat less than happy that their Samsung is not quite as unlocked as they thought.
  • Actually, not all phones are bootloader locked from the factory. I recently learned that all T-Mobile G3s come unlocked.
  • I think you're making a mistake in the difference between unlockable (aka unencrypted) and unlocked.
  • I thought that too, but it's actually unlocked from the factory. No unlocking needed.
  • You lie. A family member of mine has that exact device and it came locked....just unencrypted.
  • Didn't believe it either, and I even have a rooted, romed, Verizon G3. http://www.droidforums.net/threads/lg-g3-all-variants-rooted-factory-unl... Posted via the Android Central App
  • So it still required root, based on reading that? The explanation is just as confusing. If not, it's a horrendous security hole to ship a phone with the bootloader already unlocked. Posted via the Android Central App
  • Yeah I find it hard to believe that G3 came unlocked from the get go which will be a security blunder. Even nexus don't come unlocked out of the box, you need to unlock it using fastboot oem unlock command. Posted via the Android Central App
  • It didn't. They are wrong.
  • Just a confusing explanation.
  • The explanation says unlockable not unlocked.. Posted via the Android Central App
  • Which is why it's confusing. http://www.androidheadlines.com/2014/09/lg-g3-users-start-petition-chang...
  • i'm on t-mobile, with a g3, it came out of the box bl unlocked. i currently have it rooted with blisspop...didn't have to bump it to do so...it came out of the box bl unlocked...the t-mobile g3 was the only g3 that was that way
  • I have a T-mobile LG G3 and it was most definitely bootloader and sim locked when i got it, cost me about $7 to get a sim unlock code and the bootloader was "unlockable" via "fastboot oem unlock" command in ADB, it was not already unlocked though
  • This. A family member of mine has the same device and I also had to unlock it for them. It's unencrypted, but very much in the locked state.
  • To the common smartphone users, this 'unlocked' term can be even more confusing. My wife's friend bought an AT&T iPhone from someone who said it was unlocked, but didn't understand that no matter how unlocked a GSM phone is, it won't work on her CDMA Verizon plan.
  • Indeed, network compatibility is also a hurdle. Less and less a problem over time here in the US, but still an issue. Posted via the Android Central App
  • Sony other manufacturers as of recent have made that easier. The new z3 and alcatel idol 3 have all the bands from att and t-mobile, including the new band 12 t-mobile is starting to roll out. Posted via the Android Central App
  • Att and tmo.........not verizon and sprint.
  • Unfortunately a little research still must be done. And questions are also good to ask. Especially on craigslist. If the person is unwilling to meet at the respective cell phone store to make sure phone can activate then that should warn you right three. Common sense can help in cases like these. Posted via the Android Central App
  • Makes me wonder how Google was able to get all carriers to sell their latest Nexus--Verizon included. This is a good thing, but were carriers really that concerned that they would lose customers if they didn't offer it? I love the phone, but honestly it doesn't have the hype or sales of Apple or Samsung. Carriers would lose many more customers if they stopped carrying the Iphone. Anyway, I hope next year's Nexus is also able to run on all the North American carriers. As an aside, the At&T Nexus 6 is the only one of the 4 that is sim locked. Assuming the bootloader is unlocked, are there custom roms out there that will unlock the sim too----as Jerry mentioned?
  • it is cool that nexus 6 can run on any network, but the IMEI, is still not available on some networks, read an article on this and depending on where u buy it, will let u know who will activate it for u. but there are work arounds. Posted via AC app on my X 14
  • Verizon phones are all factory (SIM) unlocked. And my only concern are the horrible carrier logos on the front of phones. I'd take the removal of those over locking and unlocking any day.
  • No logo on the front of the 6
  • iphone 6?
    galaxy s6?
    nexus 6?
  • Mazda 6? Posted via the Android Central App
  • +1 Posted via the Android Central App
  • +6 Posted via the Android Central App
  • There are a number of Verizon phones not unlocked. Most current Verizon 4GLTE phones are unlocked. Also keep in mind that not all Verizon 4GLTE phones have gsm radios,meaning they won't work on any gsm carrier. Posted via the Android Central App
  • 1. they are NOT all unlocked. some are, some are definitely NOT. 2. even if it is sim unlocked the chances of using it on anotger carrier for more than 2g are slim to none.
  • All Verizon smartphones after 2012 are factory unlocked. I'd be interested to see your evidence to the contrary. Posted via the Android Central App
  • I think we should care more about unbranded phones without carrier junk, meaning no carrier customization firmware. Don't let the carrier crap up the device, but unfortunately people don't seem to care with sub par experience on a carrier modified device. Posted via the Android Central App
  • Or maybe they don't care because they don't feel the experience is sub par on a carrier modified device.
  • Or that device should have an unlockable bootloader, so that crapware can be uninstalled. Posted via the Android Central App
  • +1 Posted via the Android Central App
  • So much this. Carrier-branded phones only serve to cause more fragmentation in an already fragmented Android ecosystem. There's also that one carrier in most countries that takes much longer than others to "test" updates.
  • I'll agree to that, if they could just release a few models of each phone like apple does
    One for North America, one for Europe and one for Asia was I think their last breakdown.
    It would definately speed up the upgrade schedule. Without the carrier crap. bypass the carrier and upgrade the phone directly via the OEM like apple or nexus phones do.
  • "That carrier" changes with every single device. Tmo took longest to update the G3. Sprint NEVER updated NS4G to the latest factory image. It's never ways the same carrier....just one more than others on most occasions.
  • I agree with this, however, most people are going to buy from their carrier... for a payment plan, a 2 year contract price, or just convenience... after all, here in the US, it's not like we have too many phone-vendor specific stores. You could argue with Apple Stores and Microsoft Stores both of those brands are more covered, but there are no Google/Android Stores.
  • Google has an online store where one may purchase Nexus devices. Posted via the Android Central App
  • I bought an unlocked moto e 2015 edition just to use as a tablet.
  • Lol. Posted from my Motorola Moto G.
  • Bought prepaid verizon Moto g for $24 after tax to use as the same thing. Posted via Android Central App on 1+1
  • thats one tiny tablet!!
  • Sometimes it comes down to money and getting the best deal you can. Posted via the Android Central App
  • Nice article,Jerry Hildenbrand! I know mine is carrier unlocked. Now if someone could figure out how to unlock the Verizon Galaxy note 4 for root purposes! lol
  • +1
  • Don't buy subsidized bullshit from carriers. There....all done!!
  • The g3 from t-mobile comes bootloader unlocked from factory. This phone on stock rom is ok but with a custom rom like nexus experience it's one of the best out there. It's sad the versions from Sprint, att and Verizon all have locked bootloaders. It wouldn't be so bad but they load so much junk into them it sucks the power right out. Posted via the Android Central App
  • I have a friend who has a G3 on T-Mo and he runs CM12 on it. He remarked how much of a beast it is and can get 6 hours of SOT on it. I have the international-SIM unlocked LG G4, known as the LG-H815, and it is officially supported by LG's new bootloader unlock tool, so if you're looking for a G4 to modify, the H815 is a worthy pick, along with the T-Mobile variant, which should have its bootloader unlocked already.
  • Ive started buying phones outright now and i make sure there sim unlocked
  • Each and every smartphone my family owns has always been SIM-unlocked.
  • Most of the reasons I know people wanna unlock the sim is because they wanna use it on Straight Talk or something like that but I personally have a unlocked phone that gets better reception (in my opinion) than an AT&T branded device, even thought my Moto G lacks LTE it gets more bars on 3G (HSPA+) than one made for AT&T gets on 3G at my house, I do get higher 3G than I do LTE because I live on the edge of a service area but I still find it funny it seems to work better lol BTW Cricket is the same as AT&T coverage wise if anyone reading this doesn't know Posted via my Moto G 2nd gen on Cricket
  • With VoLTE will you eventually be able to use verizon and Sprint like GSM networks At&t and tmobile? Since all 4 networks use Sim cards for LTE?
    Is it possible to have 2 carriers on one sim? Could there be a mvno that has tmobile and att on one sim? Posted via Android Central App on 1+1
  • Sprint's LTE network is incompatible with the other LTE networks, even though all LTE networks utilize SIM cards. Also, each LTE network comes in different frequency bands, which need to be supported by the smartphone.
    Do not think it is possible for 1 SIM card to hv 2 LTE carriers.
  • Project Fi is doing it somehow
  • And they are doing it well. I look at it as a beefed up T-Mobile/Sprint Network. Only been on it two weeks, but not let down. Posted via the Android Central App
  • They all use different bands, nothing specific about Sprint makes is more incompatible than the others. Sprint is working on LTE roaming agreements with several small rural carriers. Posted via Android Central App
  • When i worked at att i had people coming in all the time to get their phones unlocked the day their contract was up. Not sure half of them actually knew what it was they just felt they needed to do it. Posted via the Android Central App
  • Increases the resale value.
  • I just want the ability to choose the applications on my phone. I paid for it and I want to delete the bloatware. No more "Updates" with additional bloatware either. Listen up Evernote and AT&T I'm talking to you. My phone came with x amount of real estate (storage) if you want to rent it...lets talk. What might a reasonable amount be for each 100K of space? Maybe the bloatware can stay once my (say $2 per app, per month) rebate checks arrive in a timely manner. P Posted via the Android Central App
  • I picked up the Maxwest Android Astro 5 (Kit Kat) from Yippz. This phone has a 5 inch screen, 1.3GHz quad core, 8.0 mp camera and is Dual SIM. It's also manufactured unlocked. I use Puretalk (at&t) for only 10 dollars a month (personal line).This phone has tethering & wi-fi built in., so I can use it at any coffee shop, restaurant, park, or who ever is offering free wi-fi. The best thing is I am not stuck in a contract and I can switch to any MVNO carrier at any time. I use one sim for personal and the other sim slot for business. It's so nice not to carry two phones.
  • Does that even real Posted via the Android Central App
  • I always buy unlocked and have SIM only contract. Higher initial outlay but saves in the long run and the phones don't come with any carrier bloatware. It's easier to buy unlocked in UK than US I think? Posted via the Android Central App
  • Wondering if the N6 I got from Project Fi is sim unlocked? Didn't even think to ask. Posted via the Android Central App
  • back in the days when i used to have a carrier contract i would immediately, upon buying a new (sim-locked) phone, call the carrier and get it unlocked. no reason to wait. it just added options. i also felt it improved resale value for a potential customer who may want to travel with it.
  • Here in Singapore it is illegal for carriers to sim lock the devices therefore, every single phone here is unlocked
  • And all carrier bloatware can be deleted as well
  • I'm having a problem that makes me wonder if there are varying degrees of "SIM unlocked". I just bought a LG G4 H811 advertised as "4G LTE T-Mobile GSM Unlocked". I notice a few T-Mobile ghosts in the machine: a TMo splash screen at startup and some TMo apps that can't be uninstalled. The phone works fine, except for two things: 1. It can't send/receive MMS texts (texts with multiple recipients or that have attachments). I've tried a gazillion suggested fixes. None worked. (For the gruesome details, see thread titled "LG G4 can't receive / send multi-party or attachment texts" on Android Forums.) 2. When I try to enable wireless calling, I get "Error 05: Invalid SIM card". My service provider is Consumer Cellular, and the SIM card they have provided uses the AT&T network. My last (desperate) hunch about these problems is that some T-Mobile software is still handling the traffic at some level in there, and it can only do MMS and wireless calling via T-Mobile. In other words, this "unlocked" phone is not completely unlocked. Help? Comments?