What is a SIM PIN code and how to unlock a SIM card with a PIN?

A SIM unlock screen
(Image credit: Jerry Hildenbrand)

What is a SIM PIN code and how to unlock a SIM card with a PIN?

Best answer: A SIM PIN code is a (usually) four-digit number used to unlock a physical SIM card. The code is supplied by your carrier and some carriers allow you to change it. You'll need to unlock your SIM card each time you start your phone or anytime you've manually locked it. You do this by entering the code in the pop-up window that appears once the phone screen is on.

Much like a lock screen PIN code, a SIM PIN code is a way to make sure nobody can use your SIM card without knowing the correct code. Whenever a SIM card with a PIN set is first placed in a phone or manually locked, you'll need to know the PIN to unlock it for use. This ensures that only someone who knows the code can access the card to make calls or send messages.

What is a SIM PIN?

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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. This ensures that a stolen phone cannot be used to make calls or prevent unauthorized access to a protected or secure phone number.

SIM PIN codes are not that common anymore, but they're often implemented in prepaid SIM cards you purchase from a store or MVNO. You can set up your phone to use the code but you will need to contact your carrier before you begin and be ready to contact them again if anything goes wrong.

Before you begin

If you are setting a SIM card PIN code for the very first time you'll need to be able to talk to the carrier who issued the SIM card. You'll need to get what's called a PUK code which the carrier provides as well as instructions about entering it; some carriers have you enter a PUK code through the phone dialer and some have you enter it during the SIM card PIN code setup.

It's best to have access to another working phone in case you're locked out and need to talk with the carrier that issued your SIM card. This is one of the few times it might be worth actually visiting a carrier store so you're not stuck waiting for a replacement to come in the mail.

Use your phone's settings

The method for setting up a SIM card lock differs based on who made your phone. You'll find it with the rest of the network settings, usually hidden behind the advanced section.

Once you've found it, you can enable the card lock and manually lock your SIM card any time you like. 

During setup or while unlocking your SIM card once it's set up, entering an invalid PIN code more than a specific number of times will lock you out of using the mobile network with that card. You'll need to contact your carrier if this happens.

Do you really want or need a SIM card PIN lock?

This doesn't affect the security of your phone in any way and is a holdover from a time when SIM card theft was more prevalent and the number of calls, texts, and data was much more limited by your carrier. In the near future, this will more than likely be depreciated.

If you have a real need for making sure nobody can remove your SIM card and use it elsewhere, this is the cure. Just be ready to make a call to customer support before you get started or in case there is a problem.

Jerry Hildenbrand
Senior Editor — Google Ecosystem

Jerry is an amateur woodworker and struggling shade tree mechanic. There's nothing he can't take apart, but many things he can't reassemble. You'll find him writing and speaking his loud opinion on Android Central and occasionally on Twitter.