An IMEI is a 15-digit identifier unique to a mobile device, made up of an 8-digit Type Allocation Code identifying the model, a 6-digit serial number and a Luhn check digit that validates the whole number.
Example
490154203237518TAC (type allocation): 49015420
Serial: 323751
Check digit: 8 ✓ Luhn validWhat is the IMEI Decoder?
The IMEI (International Mobile Equipment Identity) identifies the handset, not the subscriber — that is the SIM's job, via the IMSI. Networks use it to allow or block a specific device, which is what happens when a stolen phone is reported and the IMEI is added to the shared blacklist: the handset is refused service regardless of which SIM is inserted.
The first eight digits are the Type Allocation Code, assigned by the GSMA to a specific make and model. Every unit of the same model shares its TAC, so the TAC tells you what the device is while the following six digits identify the individual unit. The fifteenth digit is a Luhn check digit — the same algorithm that guards credit card numbers.
You will also meet IMEISV, a 16-digit variant where the check digit is replaced by a two-digit software version number. Dialling *#06# displays the IMEI on virtually any phone.
How to use the IMEI Decoder
- Enter the 15-digit IMEI, from *#06#, the settings screen or the SIM tray.
- Check that the Luhn validation passes.
- Read the TAC to identify the device model the number belongs to.
When to use it
- Verifying an IMEI on a second-hand phone listing before buying.
- Confirming the IMEI in an insurance or police report is transcribed correctly.
- Checking that a device management inventory holds valid identifiers.
IMEI Decoder at a glance
| Length | 15 digits (IMEISV is 16) |
| TAC | First 8 digits — identifies make and model |
| Check digit | Last digit, Luhn algorithm |
| Display | Dial *#06# on the handset |
Frequently asked questions
What is the difference between IMEI and IMSI?
The IMEI identifies the physical handset; the IMSI identifies the subscriber and lives on the SIM. Swapping SIMs changes the IMSI and leaves the IMEI unchanged.
Can an IMEI be changed?
It is stored in device firmware and is illegal to alter in many jurisdictions, though it is technically possible on some hardware. That is why blacklists are shared between networks rather than relying on the device alone.
Does a valid IMEI mean the phone isn't stolen?
No. Luhn validation only proves the number is well-formed. Blacklist status must be checked against a national or GSMA database — this decoder cannot tell you that.
What does the TAC tell me?
The make and model. All units of the same model share a TAC, so it identifies the device type but not the individual handset.
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