SIMlocked

SIMlocked (also written as SIM-locked) is a designation for mobile devices whose firmware restricts operation to SIM cards from a particular carrier or region. A SIM-locked device will typically refuse to connect to networks other than the one it was sold for, preventing use with foreign SIM cards until the lock is removed. Locks are most common on smartphones and tablets obtained under carrier plans or subsidies, but can appear on other cellular-enabled devices.

Locking is implemented at the software level, often through carrier-specific unlock keys or by configuring the device to accept only certain network profiles. The result is that when a user inserts a SIM from a different carrier, the device displays an error or requests an unlock code. Some devices also restrict mobile data or features until unlocked.

Carriers set SIM locks to protect subsidies, reduce churn, and preserve control over the device’s lifecycle. Locks may be time-limited and lifted automatically after the customer fulfills contract terms or pays off device financing; in other cases, devices sold outright may be locked permanently or until the user requests an unlock.

Unlocking can be performed through official channels provided by the carrier or manufacturer, sometimes after meeting eligibility criteria. In many jurisdictions, carriers publish their unlock policies, and some regulations require unlocking after a service term ends. Third-party services exist but can carry warranty, security, or legality risks.

The landscape has shifted with the rise of eSIM and increasingly device-agnostic sales, leading to more models sold unlocked or with flexible unlocking terms. Availability and rules vary by country, carrier, and device.