How do I check if an iPhone is carrier-locked by IMEI, and what does "Unknown" mean?

Dial *#06# on any phone and the IMEI appears on screen. On an iPhone it is also under Settings > General > About, where dual-SIM models show IMEI and IMEI2 (either one can be checked). On Android it is under Settings > About phone. A serial number works too for Apple checks; Wi-Fi-only iPads, Macs and Apple Watch have no IMEI and are checked by serial.

On iOS 14 and later, Settings > General > About has a Carrier Lock line. "No SIM restrictions" means the phone is unlocked; anything else means it is locked. It costs nothing, but it has two limits: you need the phone in your hand, and it does not tell you which carrier the phone is locked to, which is exactly what you need to know before ordering an unlock.

An IMEI check reads the activation policy Apple holds for the device. The Carrier line names the network the device is locked to, for example "US Spectrum Mobile Locked Policy" or "US Verizon Locked Policy". A value of "Unlock." means the device is factory unlocked. Some unlocked units show a policy name such as "Multi-Mode Unlock" instead; the word Unlock in the policy is what matters.

The same check usually returns a few more lines that help when buying a used phone: the warranty status, whether the unit is a demo or a replacement, whether MDM (a management profile) is on, whether Find My is on, and how many Apple support cases exist for it. A full GSX report goes further and shows the Applied Activation Policy together with the Unlock Date for units that were unlocked later; the Next Tether check shows the Initial, Applied and Next Tether policies side by side, which reveals a phone that was sold locked and unlocked afterwards.

Field coverage depends on what Apple holds for the device. When the Carrier line is missing from a result, or a database-style checker prints "Unknown", it means there is no lock record on file, not that the phone is unlocked. The common causes: the device was never activated (a sealed unit has no applied policy yet), the policy belongs to a regional or prepaid carrier that is reported less consistently than the big networks, or the checker you used relies on a carrier database rather than on Apple's activation record. Whatever the cause, "Unknown" is a statement about the checker's data, not about the phone.

What to do: run a check that reads the Apple activation policy itself (the Carrier + SIM-Lock check or a GSX report). If the policy line is still missing there, the phone has no record to read, and the practical test is to put in a SIM from another carrier after activation. A missing line is a valid result and not a refund case; the check still returns everything else Apple holds.

Apple keeps the activation policy for every iPhone centrally, so one check by IMEI or serial covers every carrier in the world. Android phones have no equivalent central record: the lock status lives in the carrier's own device database, so the check has to be carrier-specific. For a Samsung, Pixel or Motorola locked to a US carrier, use the carrier's eligibility check: T-Mobile (ESN Status, Contract Status, Sprint Device), Verizon (Device Status, ESN Status, Unlock Eligible), Cricket (block flags, SIM Locked, unlock verdict), or the AT&T clean unlock + status check, which reports the AT&T status when it cannot unlock. The GSMA blacklist check works for any IMEI, Android or iPhone, because the lost-or-stolen database is keyed by IMEI rather than by manufacturer.

A locked phone works on its own carrier and refuses other SIMs. A blacklisted phone has a lost, stolen or fraud report in the GSMA database and refuses to register on any network that reads the list, even on its own carrier. The carrier-lock check does not show blacklist status and the blacklist check does not show the lock; a phone can be factory unlocked and still blacklisted, or locked and perfectly clean. Before buying a used phone, run both, and if it is locked, check the carrier-level status (unpaid bills, active account) with the carrier's own check before paying for an unlock.