What is a SIM Pin?

S. Gonzales

A SIM PIN is a password that allows an administrator user of a phone to access information on his SIM card. The password is usually between four and eight digits. These PINs act like ATM PINs in that they require a user to authenticate himself as the true owner of the card before information is released.

SIM card.
SIM card.

Sometimes, an automatic SIM PIN is dispatched upon activation of a new phone. However, many cell phone companies allow customers to choose a SIM PIN upon initial registration. If an automatic PIN is assigned to a new customer, the customer may opt to change the PIN to a numeric combination that is easier for him to remember. Some companies may also allow users to deactivate the requirement of PIN use either directly on cell phone menu options or by calling customer service and putting in a formal request.

SIM card being placed into a mobile phone.
SIM card being placed into a mobile phone.

Some phones may come equipped with a PIN Unblocking Key (PUK) number. Should a user forget his PIN, he will be prompted to enter the PUK number into his phone so that he may easily retrieve his PIN. If the user enters his PUK number incorrectly after a set number of times, a SIM card may respond my permanently disabling itself and necessitating that the user buy another SIM card. However, should a user enter his PUK correctly, the user will be automatically provided with his PIN.

Some sim cards are packaged inside of a larger card in order to protect them from damage before use.
Some sim cards are packaged inside of a larger card in order to protect them from damage before use.

Choosing a secure SIM PIN is an important part of keeping the information located on the SIM card safe. Users should take time during the selection process to ensure that they have chosen a PIN that is both hard to guess by outsiders and easy to recall. Users should avoid choosing PINs that utilize the same digits found in their ATM or credit card PINs. Using birthdays and the last four digits of Social Security numbers is also not advised.

Customer service representatives of cellular phone companies may require that users provide a SIM PIN before answering any questions about a specific cell phone or an account. Similarly, technical support may be contingent upon receipt of a correct SIM PIN. While providing a SIM PIN each time a user wants customer or technical support may seem unnecessary, the requirement acts as an extra security measure that keeps a user's personal information and contacts safe from would-be identity thieves.

Some cell phone companies allow customers to select a SIM pin.
Some cell phone companies allow customers to select a SIM pin.

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Discussion Comments


I used to work for a cell phone carrier and people would call in all the time not knowing their pin. They would get upset when I would tell them I could not release any information about their account until they knew it.

They got even more upset when I told them if they could not call back with the correct pin that they would have to do a sim pin unlock, which was a long and tedious process. I do not think some people realized that the sim pin is in place to protect them. All I can say is when you get your phone and you set up your pin, write it down in a safe location.


How much information is stored on a SIM card nowadays? The article mentions contacts, but I think that phone storage (even in the pre-smartphone days) offers a lot more flexibility for storing contacts than if they're stored on the sim. Would they still be protected by the SIM pin code?

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