This ensures that a stolen phone cannot be used to make calls or prevent unauthorized access to a protected or secure phone number. Very simply, a SIM PIN is a code, usually between four and twelve digits, that prevents a SIM card from being used if placed in a new phone, or after rebooting a phone it's currently inserted into.

Why you can trust Android Central Our expert reviewers spend hours testing and comparing products and services so you can choose the best for you.