What is an IMEI number and how does it work?
Every mobile device that connects to a cellular network carries an International Mobile Station Equipment Identity, commonly known as an IMEI. This 15-digit number serves as a unique digital fingerprint for the hardware. Network operators, manufacturers, and law enforcement agencies use it to identify genuine equipment and prevent stolen handsets from accessing mobile networks.
The structure of an IMEI is strictly regulated by the GSMA. The first eight digits form the Type Allocation Code (TAC), which identifies the specific model and country of manufacture. The subsequent six digits represent the individual serial number assigned by the manufacturer. The final digit is a checksum calculated using the Luhn algorithm, which validates the integrity of the preceding fourteen digits. Dual-SIM handsets and devices with active eSIM functionality possess two distinct IMEI numbers, one for each modem channel.
When you insert a SIM card or activate an eSIM, your handset transmits its IMEI to the local mobile network tower. The carrier validates this code against global registries. If the identifier appears on a shared equipment blacklist, the network instantly rejects the connection, preventing the device from making calls, sending SMS messages, or using cellular data.
How to find your 15-digit IMEI number
Retrieving your device identifier takes only a few seconds. Depending on whether you have physical access to the phone or are inspecting it remotely, several reliable methods exist.
The fastest universal method across Android, iOS, and basic feature phones is the universal dialler code:
- Open the phone or dialler app on the handset.
- Type *#06# on the keypad.
- A screen will immediately pop up displaying the device IMEI, barcode, and serial number. You do not need to press the call button.
If the device does not respond to dialler codes, you can locate the number within the operating system settings:
- Apple iOS: Open Settings, tap General, and select About. Scroll down until you find the IMEI entry.
- Android: Open Settings, select About phone (or About device), and tap Status information to view the IMEI slots.
For broken, locked, or unpowered handsets, check the physical hardware. Manufacturers print the 15-digit string on the SIM card tray, etch it onto the rear glass casing, or print it on a label underneath removable batteries. You will also find the original identifier printed near the barcode on the retail box.
What a free IMEI check reveals about a handset
Running an identifier through a dedicated lookup tool produces immediate technical and administrative data. You can perform an IMEI check free without creating an account or providing payment details.
A standard lookup cross-references the Type Allocation Code against manufacturing records to verify:
- Exact make and model: Confirms whether an advertised 256GB iPhone 15 Pro is genuine or an older chassis retrofitted with cheap aftermarket components.
- Full technical specifications: Displays processor type, RAM configuration, screen dimensions, original release date, and cellular band compatibility.
- Carrier and network lock status: Identifies if the phone was originally tied to a specific network such as EE, Vodafone, or O2.
- Warranty coverage: Indicates remaining manufacturer guarantee periods and eligibility for service programmes.
- Reported blacklist indicators: Flags whether an operator has marked the hardware as lost, stolen, or blocked due to unpaid billing agreements.
Using Device Decoded lets buyers verify these critical details instantly across iPhone, Android, and cellular-enabled tablets before committing to an exchange.
Free IMEI lookups versus commercial background checks
Understanding what different lookup services provide helps you choose the right tool for your situation. Free tools provide essential hardware specifications, model validation, and surface blacklist indicators. Paid commercial registries offer deep insurance-loss histories and police database integrations.
| Information Type | Free IMEI Lookup | Paid Commercial Registry |
|---|---|---|
| Make, model, and colour verification | Yes | Yes |
| Hardware specifications and storage capacity | Yes | Yes |
| Basic blacklist and network status | Yes | Yes |
| Manufacturer warranty details | Yes | Varies by provider |
| Insurance write-off records | No | Yes |
| Account registration required | No | Yes |
| Cost per search | Free (£0) | £2 to £10 |
For most private marketplace transactions on platforms like eBay, Gumtree, or Facebook Marketplace, a free lookup provides sufficient data to weed out blatant fakes, stolen units, and mislabelled hardware.
Warning signs to look out for when buying used phones
Fraudsters frequently target the second-hand electronics market. Knowing what discrepancies to look for during an inspection protects your money.
Always compare the IMEI on the software screen with the physical SIM tray and outer box. If the number returned by dialing *#06# does not match the etching on the SIM tray or casing, the device has likely undergone unauthorised repairs, housing swaps, or motherboard replacements. Walk away immediately from any deal where numbers conflict.
Be cautious if a seller refuses to provide the IMEI prior to meeting. While sellers may obscure serial details in public listings to prevent malicious reporting, a genuine private seller should share the 15-digit number privately via direct message. Once you receive it, check the details against official model releases.
Another common issue involves delayed blacklisting. A seller may sell a phone on an active contract, collect your cash, and then report the handset lost or stolen to claim insurance days later. Always request the original proof of purchase or a formal receipt confirming that the handset is fully paid off.
IMEI numbers versus serial numbers
While people often use the terms interchangeably, serial numbers and IMEI numbers serve distinct functions within consumer electronics.
A serial number is an internal tracking code created entirely by the manufacturer. Apple, Samsung, Google, and Sony use serial codes to track production batches, assembly plant locations, and warranty claims through their own repair networks. Serial numbers do not follow a globally standardised format, nor do they communicate directly with mobile phone masts.
An IMEI number is an internationally standardised telecommunications identifier. Wi-Fi-only tablets, laptops, and smart speakers carry serial numbers but lack an IMEI because they contain no cellular radio hardware. If a mobile device includes cellular antennas, it will carry both a serial number for manufacturer tracking and an IMEI for network management.
When verifying warranty status directly through manufacturer support portals, a serial number check is often requested. For network blocking, roaming checks, and carrier compatibility, the IMEI is the only identifier that matters.