What Is Stored on a SIM Card?

What Is Stored on a SIM Card? (And What Isn't)

A SIM card stores the small set of data that proves to your carrier who you are: your subscriber identity, a secret security key, the card's serial number and some network settings. It can also hold a limited number of contacts and text messages. It doesn't store your photos, apps, passwords or browsing history. Those live on your phone or in your cloud account.

Below is every item a SIM holds, the part most guides get wrong (your phone number), how much actually fits, and where the rest of your data really lives.

What a SIM card stores

Almost everything on a SIM is written by your carrier, not by you, and each item has a role in how a SIM card works: telling the network which line is yours and proving the card is genuine.

Is your phone number stored on the SIM?

Not in the way most people think. Your phone number belongs to your account with the carrier, and the carrier's records link that number to your SIM's IMSI. That link is why the number follows the SIM when you move it to another phone.

The SIM standard does reserve space for a copy of the number: 3GPP, the body that writes mobile network standards, lists it as the EF MSISDN file in its USIM specification. But that copy isn't what routes calls to you. Your number can change while the IMSI stays the same, and a carrier can link a different number to the same SIM.

This is also why SIM swap fraud targets your carrier account rather than your card. SIM swap fraud is when a criminal gets a carrier to move your number to a SIM or eSIM they control, to intercept calls and verification codes.

Contacts and texts on a SIM card today

Storing contacts on the SIM is a leftover from older phones. They're saved as simple name-and-number pairs, so there's no room for an email address, photo or notes. Early SIMs held as few as 20 contacts and five texts; modern cards can usually store over 250 contacts.

On iPhone

Apple's support guide states plainly that "Your iPhone doesn't store contacts on the SIM card." It can still read contacts that an older phone saved there and copy them into your Contacts app:

1. Insert the SIM card that has your contacts on it.

2. Open Settings, tap Apps, then tap Contacts.

3. Tap Import SIM Contacts. If asked, choose where to save them.

4. When the import finishes, open the Contacts app and check they're there.

Apple notes that what gets imported depends on how your previous phone stored the contacts on the SIM, so some details may be missing.

On Android

Android phones usually save new contacts to your Google account or to the phone itself, not to the SIM. Most Contacts apps can still import contacts from a SIM: open the Contacts app's settings, look for an Import option and choose the SIM card. Menu names vary by phone brand and Android version.

How much data can a SIM card hold?

Very little. SIM cards come in capacities from about 8 KB to at least 256 KB. A single photo from a modern phone is often several megabytes, which is many times more than an entire SIM can hold.

The size of the card doesn't change this. Standard, micro and nano SIMs use the same chip, and smaller formats simply trim away more of the plastic.

You'll see different figures quoted online, from 4 KB to 512 KB. Treat any exact number as typical rather than guaranteed: capacity depends on the specific card your carrier issued.

What a SIM card never stores

• Photos, videos and music

• Apps and app data, including chats in WhatsApp, iMessage or other messaging apps

• Passwords, including Wi-Fi passwords

• Browsing history

• Call history and emails

These live in your phone's storage, a memory card or your cloud backups. Given how small a SIM's memory is, most of them couldn't fit on one anyway.

Where your data actually lives

The easiest way to understand a SIM is to see what goes with it when it moves to another phone and what stays behind.

So when you put your SIM in another phone, your line goes with it: calls, texts and mobile data. Everything else stays on the old phone.

What an eSIM stores instead

An eSIM (embedded SIM) is a SIM chip built into a device that downloads and stores mobile plans digitally, so you can add a plan without inserting a physical SIM card. Each downloaded plan is a profile. According to eSIM security company Kigen, a profile carries the same kind of identity a physical SIM does: the ICCID, IMSI and Ki, network settings such as the APN and preferred networks, and roaming rules.

This is exactly how a travel eSIM from eSIM70 works: you download a plan for your destination, and its profile carries everything the network needs to let you connect, with no card to collect or swap.

The difference is the container, not the contents. A phone can hold more than one eSIM profile on the same chip, and because the chip can't be removed, a thief can't pull your line out of a stolen phone and use it elsewhere. That's one of the security trade-offs of eSIM vs SIM, alongside differences in setup and switching phones.

A newer design, the integrated SIM (iSIM), moves the same job into a device's main processor.

How to check what's on your SIM

On iPhone

Go to Settings > General > About and scroll down. According to Apple, you'll find the ICCID there, along with the EID if your iPhone uses eSIM. Each eSIM plan also appears as its own line in Settings > Cellular, the same place you finish when you add an eSIM to your iPhone.

On Android

Go to Settings > About phone. Many phones show SIM details there, such as the phone number and network, sometimes under a SIM status entry. The exact wording depends on the brand. Any eSIM plans are listed in the phone's SIM settings next to your physical SIM, which is also where you start when you install an eSIM on Android.

Phone settings only show a few identifiers. A SIM card reader can show more of the card's files, but not the Ki: the card is designed so that key can't be read out.