Buying a used phone feels like a gamble. You're staring at a sleek piece of glass and aluminum, wondering if it's going to actually work when you pop your SIM card in, or if it's just a very expensive paperweight tied to a carrier you hate. Honestly, the biggest headache in the secondhand market is the lock status. You might hear people talk about "jailbreaking" or "unlocking" as if they're the same thing—they aren't. Not even close. If you're trying to figure out how do you know if an iPhone is unlocked, you need more than just a quick glance at the settings. You need to know what the hardware is actually telling the network.
It’s frustrating.
Apple makes things look simple, but the "activation policy" living deep inside your phone's software is a complex gatekeeper. It decides whether you can swap from AT&T to T-Mobile or use a local physical SIM when you're landing in London. Most people assume that if they paid full price, it’s unlocked. That isn't always true. Sometimes, "Flex policies" at big-box retailers lock the phone to the first SIM card inserted into the tray. Yeah, it’s a mess.
The Settings App Trick (And Why It Sometimes Lies)
The fastest way to check is usually right in your pocket. Since iOS 14, Apple actually added a specific field for this. Go to Settings, tap General, and then hit About. Scroll down until you see "Carrier Lock." If it says "No SIM restrictions," you’re golden. Usually.
But here’s the kicker: sometimes that menu is just wrong.
I’ve seen iPhones that were officially unlocked by a carrier like Verizon, yet the settings menu still showed a restriction because the phone hadn't checked back in with Apple’s global activation servers. It’s a cached status. If you see a carrier name there but you know the phone should be free, it might just need a "handshake" with a new network to update that text.
On the flip side, if it says "SIM Locked," you are definitely tethered to a specific provider. This means the phone’s IMEI (International Mobile Equipment Identity) is flagged in Apple’s database to only accept a specific IMSI range. Basically, the phone and the cell tower have a secret handshake, and if your SIM doesn't know the password, no bars for you.
The Physical SIM Swap: The Only 100% Way
If you want to be absolutely certain, stop clicking through menus and start poking things with a paperclip. This is the gold standard. To really answer how do you know if an iPhone is unlocked, you need two SIM cards from two different carriers.
Borrow one from a friend. It doesn't even need to be an active, paid-up account; it just needs to be a "live" SIM from a different network.
- Power down the iPhone.
- Pop the tray.
- Swap your current card for the "foreign" one.
- Boot it back up.
If the phone immediately finds a signal or shows the carrier name in the top corner, you’re in the clear. However, if a big white screen pops up saying "Activation Required" or "SIM Not Supported," that phone is locked tight. It’s an immediate, hardware-level rejection. It’s also worth noting that with the move toward eSIM in the iPhone 14, 15, and 16 series in the US, this "physical swap" is getting harder. In those cases, you’d have to try downloading a "travel eSIM" from an app like Airalo or Ubigi. If the eSIM installs and connects, the phone is unlocked.
Understanding the "Reseller Flex Policy" Trap
This is the part that trips up even the tech-savvy. You go to a store like Best Buy and buy a "Universal" iPhone. You pay the full $900 or whatever the sticker price is. You think, "Hey, I paid retail, this must be unlocked."
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Nope.
Many iPhones sold at third-party retailers use a "Flex Policy." The phone is technically "un-configured" sitting in the box. The moment you put a SIM card in it, it "folllows" the policy of that carrier. If you put a Verizon SIM in first, it might stay unlocked (due to specific FCC rulings regarding Verizon’s spectrum). If you put an AT&T SIM in first, that phone might instantly lock to AT&T for the duration of its life until you request a formal unlock. It’s a sneaky way carriers keep you in the fold.
Using IMEI Checkers (The Good, The Bad, and The Scammy)
You’ve probably seen websites claiming they can check your lock status for $5. Or maybe they offer a "Free IMEI Check." Be careful.
Your IMEI is a 15-digit serial number unique to your device. It’s like a Social Security number for your phone. When you put that number into a random website, you’re handing over the keys to the castle. Some sites are legitimate—like SickW or GSX-based reporting tools—but many are just harvesting data to sell or to try and "re-shell" blacklisted phones.
A legitimate IMEI report will show the "Next Tether Policy." This is the technical term for which carrier owns the rights to that device. If the report says "Multi-mode Unlock," you’re safe. If it lists "US Reseller Flex Policy," you better check which SIM went in first.
Why is my phone still locked if I paid it off?
This happens all the time. You finish your 24-month installment plan with T-Mobile. You think the phone magically unlocks itself the second that final payment clears. It doesn't.
Carriers rarely "push" an unlock automatically. You usually have to go to their website or call their support line and explicitly ask for it. They then send a request to Apple's servers. Once Apple updates the database, your phone receives a tiny packet of data the next time it connects to Wi-Fi, telling it "Hey, you're free now." If you haven't done this, your phone is still locked, regardless of your balance.
What About Blacklisted vs. Locked?
Don't confuse a carrier lock with a blacklist. This is a massive distinction when you're trying to figure out how do you know if an iPhone is unlocked.
- Locked: The phone works, but only with one carrier. You can fix this by calling the carrier or paying a service.
- Blacklisted (or "Bad ESN"): The phone has been reported lost or stolen, or there is a massive unpaid debt on the account.
A blacklisted phone might be "unlocked" in the sense that it isn't tied to a carrier's software, but it’s "blocked" from the entire national network. In the US, carriers share a database (the GSMA blacklist). If an IMEI is on that list, no US carrier will give it service. Period. You could have an "unlocked" phone that is essentially a Wi-Fi-only iPod Touch. Always check the blacklist status on sites like Swappa’s free IMEI checker before worrying about the carrier lock.
The International Factor
If you're buying a phone from overseas, things get even weirder. A phone from Japan might have different "shutter sound" laws, and a phone from China might have physical dual-SIM slots instead of eSIM. But the locking rules are mostly the same. However, some international carriers don't use the same database as US carriers.
I’ve seen iPhones that were "unlocked" for use in Europe but would not activate on US carriers because they were originally sold under a "Regional Lock" policy. This is rare with modern iPhones, but it’s a ghost in the machine you should be aware of if you’re a frequent traveler.
How to Get an iPhone Unlocked Once You Know It’s Not
So, you did the check. You went to Settings > General > About, and it says "SIM Locked." What now?
You have to go to the source. If it’s an AT&T phone, you go to their specific unlock portal. You’ll need the IMEI and the phone number of the original account (usually). If you aren't the original owner, this is where things get tricky. AT&T is notoriously strict. Verizon is generally the easiest, as they automatically unlock most devices after 60 days of active service.
If the carrier refuses, there are "third-party" unlocking services. These guys basically have "moles" or "whitelisted accounts" that have access to the GSX (Global Service Exchange) portal. They charge a fee—sometimes $20, sometimes $150—to manually move your IMEI from the "Locked" list to the "Unlocked" list in Apple's database. It’s a gray market, and it’s hit or miss.
Actionable Steps for Your Next Purchase
Don't just take the seller's word for it. People lie, or more often, they just don't know any better. They think because they used it on two different prepaid brands (that both happen to use the T-Mobile network) that the phone is "unlocked."
- Check the About Screen first. It’s the easiest indicator of the current software state.
- Run the IMEI through a blacklist checker. Use Swappa or a similar reputable tool to ensure the phone isn't stolen.
- Do the SIM swap. Carry a SIM card from a different network in your wallet when meeting a seller.
- Verify the "Find My" status. A phone that is "unlocked" but has "Find My iPhone" turned on (Activation Lock) is even worse than a carrier-locked phone. It's totally unusable if the seller doesn't log out.
- Contact the carrier. If you have the IMEI, you can sometimes call the carrier’s support line and ask, "Is this device eligible for unlocking?" They won't give you personal info about the previous owner, but they will tell you if the device is clear.
Basically, if you're buying a used iPhone, you're doing detective work. Look for "No SIM restrictions" in the settings, but verify it with a physical card. If you're selling your phone, do the right thing and call your carrier to request the unlock before you list it. It increases the resale value by at least $50 to $100 anyway.
The reality is that "unlocked" is a software state, not a hardware one. Every iPhone 15 is physically capable of running on every network, but the software is a bouncer at the door. Make sure your phone has the right credentials to get past the velvet rope. Once you've confirmed that "No SIM restrictions" message and verified it with a live swap, you can breathe easy knowing you actually own your hardware rather than just renting it from a carrier.
Keep in mind that if you're dealing with an older device (like an iPhone 6 or 7), some hardware versions were actually different (GSM vs CDMA). But for anything made in the last five or six years, the only thing standing between you and any carrier in the world is that digital "unlocked" status in Apple's database. Check it, verify it, and then enjoy the freedom of switching carriers whenever a better deal comes along.