SIM lock
SIMロック shimu rokku
A restriction that ties a phone to one carrier. New phones sold in Japan are now generally sold without it, but older devices may still be locked.
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Related guides
Activation / kaitsū開通kaitsū
The step that switches your line onto the new SIM and network. Until activation finishes, the new SIM has no service.
eSIMeSIMī-shimu
A SIM built into the phone that you activate by scanning a code or through an app — nothing physical is shipped.
SIM cardSIMカードshimu kādo
The small chip that connects your phone to a mobile network. Comes in a physical form you insert.