4 minute read

What is on a SIM card?

Krista

By Krista

Travel & Tech Writer

What is on a SIM card?

In many of our junk drawers or “fancy garbage” drawers, there lies a neglected SIM card. But have you ever wondered what is on a SIM card?

They are often tossed in without a second thought as to what is actually stored on them, or whether it even matters once they’re removed. So, what is on a SIM card?

As it turns out, there actually might be more to your SIM card than you’d expect. 

What information is on a SIM card?

A small chip that connects your phone to your carrier's network, a SIM card doesn't hold your photos or your apps, but it does carry the data essential to how your phone operates. Here's exactly what information is stored on your SIM card.

IMSI (International Mobile Subscriber Identity)

This is the unique identifier assigned to you as a phone subscriber. A 15-digit number that tells the network who you are, the IMSI connects your device to your carrier thereby allowing calls, texts, and data to work. It never changes and is never visible to you directly.

ICCID (Integrated Circuit Card Identifier)

Functionally a SIM card's serial number, this is a unique identifier for the physical card itself (and not you as a subscriber). This is what allows carriers to track and manage individual SIMs.

Authentication key (Ki)

This is a secret encryption key stored on the SIM that will verify your identity with the network whenever your phone connects. Virtually impossible to extract, this is a significant part of what makes SIM-based authentication reliably secure.

Carrier and network

A SIM stores data about its network, the networks on which it's allowed to roam, and the settings required to connect.

Contacts (sometimes)

Note that older phones did store contacts directly on the SIM card. SIM-stored contacts are limited in number and detail (think: name and phone number only). These days, most people opt to store contacts in the cloud or on the device itself.

SMS messages (sometimes)

Select carriers and sometimes older devices will store a limited number of text messages directly on the SIM; however, this is increasingly uncommon. 

What is not stored on a SIM card?

Contrary to what  you might expect, your SIM card actually does not store:

  • Photos or videos
  • Apps or app data
  • Emails
  • Browsing history
  • Passwords or payment information
  • Call logs 
  • Social media accounts or content

Keep in mind that if you lose your SIM card, you won’t also lose any of this important information. If you switch to an eSIM, all your apps, photos, and personal data still remain on your device. 

Does removing a SIM card delete the data on it?

You'll find it reassuring to know that removing a SIM card does not affect any of the data it stores. Your IMSI, ICCID, authentication key, and any contacts that might be on the card remain intact when it’s not in your device.

Physically removing a SIM card only disconnects your phone from the network. The chip itself continues to hold anything it stores. 

A SIM card can be deliberately overwritten; this requires specific software and wouldn’t happen accidentally. If you’re just swapping out SIM cards between phones, the data is safe. 

What is on a SIM card and how to go plastic free

Consider that a SIM card is a small piece of plastic with a finite life. More often than not, they end up in a drawer or a landfill.

On the other hand, an eSIM is a digital version of a SIM card, storing all the same essential information digitally, directly on your device, with no physical card required. If you're travelling soon, consider making the switch to eSIM before your next trip!

Go ahead … travel the world, never pay roaming charges

Shop aloSIM in the app or online

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