Most buyers treat the IMEI as a password to a stolen-phone database. Type it in, get a green tick, move on.
It’s considerably more useful than that, and considerably more limited. The number itself encodes what the phone claims to be, which means it can expose a device lying about its own model before you’ve looked up anything at all.
What the fifteen digits actually contain
An IMEI isn’t random. It has structure.
The first eight digits are the Type Allocation Code. This identifies the make and model — not the individual phone, but the model line it belongs to. Every unit of the same model shares the same TAC.
The next six digits are the serial portion, unique to that individual device within its model.
The final digit is a check digit, calculated from the preceding fourteen using the Luhn algorithm — the same checksum scheme used on payment cards. It exists to catch typos, and it means a randomly invented IMEI will almost always fail validation.
Two practical consequences fall out of that structure.
First, you can sanity-check an IMEI without any database. Most free IMEI validators do the Luhn arithmetic instantly, and a number that fails it was made up rather than mistyped.
Second — and this is the useful one — a TAC lookup tells you which model the number belongs to. If the TAC decodes to one phone and you’re holding a different one, the IMEI has been reprogrammed. That’s a check that costs nothing and catches a whole category of fraud that a blacklist lookup sails straight past.
Where to find it, and why you check three places
Dial `*#06#`. Works on essentially every phone, usually without unlocking it.
Settings. iPhone: General > About. Android: About phone > IMEI.
The hardware. Etched on the SIM tray on many models, printed under the back cover on older ones, and on the original box.
You check all three because they come from different places. The dialled code reads the modem. Settings reads the operating system. The etching is physical and can’t be edited by software. When those agree, the phone’s identity is consistent. When they don’t, something has been swapped or reflashed.
Dual-SIM devices carry two IMEIs, and eSIM slots have them too — a phone with one physical slot and one eSIM still reports two. Check both. Regulators increasingly validate that a device’s multiple IMEIs actually belong to the same handset; Pakistan’s system runs exactly this check against manufacturer records, and mismatches get held or rejected.
Checking the check digit by hand
You’ll never need to do this manually, but understanding it explains why invented numbers fail.
The Luhn calculation works from the right. Take the fourteen digits before the check digit, double every second one moving leftward, and where doubling produces a two-digit result, add those two digits together. Sum everything. The check digit is whatever value makes that total reach the next multiple of ten.
Try it on a made-up number like 490154203237518 and you’ll find the arithmetic either resolves or it doesn’t. Real IMEIs resolve. Numbers typed from memory, guessed, or generated carelessly usually don’t.
Why this matters to a buyer: a seller quoting an IMEI over messages that fails validation has either mistyped it or invented it, and you’ve learned something before travelling anywhere. Any free IMEI validator does this arithmetic instantly.
IMEI, serial, MEID, EID — which is which
These get used interchangeably and shouldn’t be.
IMEI identifies the device to mobile networks. Standardised across manufacturers, fifteen digits, one per SIM identity.
Serial number is the manufacturer’s own identifier. This is what warranty and coverage lookups want, and it’s usually what resolves to a purchase date and a precise model configuration.
MEID is the older identifier used on some networks, fourteen hexadecimal characters. You’ll occasionally see it listed alongside the IMEI on devices that supported those networks.
EID identifies the eSIM chip itself, not the phone. Thirty-two digits. It matters when a carrier is provisioning an eSIM profile and almost never otherwise.
For used buying, you want the IMEI for blacklist and regulator checks, and the serial for manufacturer lookups. Asking a seller for the wrong one wastes a round of messages.
What happens to the IMEI when a phone is repaired
A question that comes up constantly and has a clean answer: the IMEI lives with the logic board.
Replace a screen, a battery, a camera, or a housing, and the IMEI is unchanged. Replace the logic board — which is what happens in some manufacturer service swaps — and the device now reports the identity of the new board. That’s legitimate, but it means the IMEI etched on an old SIM tray or printed on the original box may no longer match.
So a mismatch between the etched number and the dialled one isn’t automatically fraud. It’s a question. The good answer involves a documented board-level repair or a manufacturer service exchange. The bad answer is a shrug.
Manufacturer replacement units are a related case: a device swapped under warranty is a different physical phone with a different identity, and its serial usually reflects that in the coverage lookup.
The four questions an IMEI can answer
Is it blacklisted? Through a regional database — the carrier or national register covering the network you’ll use. Covered in depth in our guide to checking whether a phone is stolen or blocked.
Is it the model it claims to be? Via TAC lookup, or by running the serial through the manufacturer. Apple’s coverage lookup resolves a serial to a specific model and its warranty state; most large Android brands offer an IMEI equivalent.
Is it under warranty? Same lookup. This also tells you when the coverage clock started, which is how you verify an open-box claim.
Is it registered where registration is required? In countries with a national device register, the IMEI is the key to that status.
One more use worth mentioning: insurance and police reports both want the IMEI, not the serial. Recording both numbers somewhere off the device, the day you buy a phone, takes a minute and is the difference between a report that can be acted on and one that can’t.
The three questions it can’t answer
Worth being blunt about, because over-trusting an IMEI check is its own failure mode.
Whether the seller owns it. The IMEI says nothing about who’s standing in front of you. A phone stolen yesterday and not yet reported returns a perfectly clean result.
Whether it’s about to be blocked. A device on an unpaid instalment plan checks clean right up until the carrier flags it, which can be months after you buy.
Anything about condition. No repair history, no battery health, no water damage, no screen state. The IMEI is an identity, not a health record. Those checks are physical and live in our fifteen-point inspection list.
A word on paid IMEI checking services
There are a lot of them, and quality varies enormously.
Free and authoritative beats paid and vague, every time. The manufacturer’s own lookup, the national regulator’s portal, and the carrier blacklist are the three sources actually connected to the systems that matter. A paid service is reselling access to some subset of those, sometimes with stale data, sometimes with none.
Where paid checks occasionally earn their fee is carrier-lock status on specific networks, and even then the reliable test is putting your own SIM in at the meetup and watching it register. My honest position: run the free authoritative checks first, and only consider paying if there’s a specific question none of them answers.
Also worth knowing: entering an IMEI on a random site is not risk-free. It’s not secret information, but there’s no reason to feed it into services you haven’t heard of.
For sellers: share it early
Worth flipping the perspective, because most advice here is written for buyers.
Putting the IMEI in your listing, or offering it in the first reply, does three things. It filters out buyers who were never serious, since the ones who run checks are the ones who intend to buy. It removes a round of messages. And it signals that you have nothing to hide, which is worth real money in a market where buyers discount uncertainty heavily.
Mask the final digits publicly if it makes you more comfortable, and share the full number once someone is genuinely interested. The information isn’t sensitive — it’s printed on the box — and treating it as a secret reads as evasive rather than careful.
Cloned IMEIs, and why they’re the nasty case
A cloned IMEI is one copied from a legitimate device onto another. Two phones, one identity.
This is genuinely difficult for a buyer to catch, because the number checks out — it belongs to a real, compliant, unblocked device somewhere. The lookup comes back clean because it’s describing the other phone.
What catches it: the TAC-versus-model comparison, the three-location match, and the manufacturer serial lookup returning a model that doesn’t match what you’re holding. In countries running multi-IMEI validation against manufacturer records, cloning also tends to surface at registration.
This is also the argument for the box and the receipt. A phone whose packaging, paperwork, and etched IMEI all agree is very hard to fake convincingly.
Veelvoorkomende fouten om te vermijden
- Checking only one IMEI on a dual-SIM device.
- Reading the IMEI only from Settings. The one screen easiest to alter on a compromised device.
- Treating a clean blacklist result as proof of ownership. It isn’t close to that.
- Paying for a check the manufacturer offers free.
- Skipping the TAC-versus-model comparison. It’s the check that catches reprogrammed identities, and almost nobody runs it.
- Assuming an IMEI check tells you anything about condition. Separate job entirely.
Veelgestelde vragen
What’s the difference between an IMEI and a serial number?
The IMEI identifies the device to mobile networks and is standardised across manufacturers. The serial number is the manufacturer’s own identifier and is what you use for warranty lookups. Most phones have both, and they’re not interchangeable.
Why does my phone show two IMEI numbers?
Because it supports two SIMs — two physical slots, or one physical and one eSIM. Each SIM identity has its own IMEI, and both should be checked.
Can an IMEI be changed?
It can be reprogrammed on some devices, which is illegal in many countries and is the mechanism behind cloned identities. Comparing the dialled IMEI against the etched one on the tray is the practical defence.
Is it safe to share my IMEI with a buyer?
Generally yes — buyers need it to run checks, and it’s printed on the box. Mask the last few digits in a public listing if you’d rather, and share it in full once someone is seriously interested.
Does a free IMEI check tell me if a phone is carrier-locked?
Sometimes, unreliably. The dependable test is inserting your own SIM at the meetup.
Should the IMEI on the box always match the phone?
Usually, and a mismatch is worth asking about rather than panicking over. A logic board replaced through a manufacturer service changes the device’s identity while leaving the original packaging unchanged, which is a legitimate explanation. An unexplained mismatch is not.
What does it mean if the IMEI returns nothing at all?
Usually a fake or heavily modified device. A phone that shows no IMEI, or a string of zeros, when you dial the code is not one to buy.
Next time you’re looking at a listing, ask for a photo of the dialled IMEI screen and run the TAC through a model lookup before you agree to meet. If the number says one phone and the photos show another, you’ve saved yourself a trip.
Ready to shop with the checks in hand? Browse what’s listed on ExploreFrag.
About the author
Emran Ahmed is the founder and CEO of ExploreFrag, a marketplace for buying and selling used phones and accessories across every brand. He got interested in the structure of IMEI numbers after seeing a listing where the dialled number belonged to an entirely different model than the phone in the photographs. He reviews listings most days and considers the TAC lookup the most underused free check available to buyers.