SIM stands for subscriber identity module or subscriber identification module. It would then follow that a SIM card contains unique information that identifies it to a specific mobile network, which allows the subscriber (like you) to use the communication features of the device.
Note: SIM also stands for ‘simulation,’ and might refer to a video game that simulates real life.
For more explanation of SIM card, Watch the video, below.
What Is a SIM Card Used For?
Almost all modern mobile phones need a SIM card in order to identify the owner and communicate with the mobile network. So, if you have, say, an iPhone on Verizon’s network, it needs a SIM card so that Verizon knows that the phone belongs to you and that you’re paying for the subscription, but also so that certain features will work.
Note: The information in this article should apply to both iPhones and Android phones (no matter who made your Android phone: Samsung, Google, Huawei, Xiaomi, etc).
You may have been in a situation where you get a used phone that’s missing a SIM card and soon realize that it doesn’t work as anything but an expensive iPod. While you might be able to use the device on Wi-Fi and to take pictures, you can’t connect to any carrier’s mobile internet network, send text messages, or make phone calls.
Some SIM cards are mobile, which means if you put it in an upgraded phone you just purchased, the phone number and carrier plan details will now “magically” start working on that phone. On that note, if your phone runs out of battery and you desperately need to make a phone call, and you have a spare around, you can just put the SIM card into the other phone and immediately use it.
The SIM also contains a small amount of memory which can store up to 250 contacts, some SMS messages and other information used by the carrier who supplied the card.
In many countries, SIM cards and devices are locked to the carrier they are purchased from. This means that although a SIM card from a carrier will work in any device sold by that same carrier, it will not work in a device that’s sold by a different carrier. It is usually possible to unlock a cell phone with help from the carrier.
What Does a SIM Card Look Like?
A SIM card just looks like a small piece of plastic. The important part is a small integrated chip which is able to be read by the mobile device it’s inserted into, and contains a unique identification number, the phone number, and other data specific to the user that it’s registered to. For more details, watch the video above.
The first SIM cards were roughly the size of a credit card and were the same shape around all the edges. Now, both Mini and Micro SIM cards feature a cut-off corner to help prevent incorrect insertion into the phone or tablet.
Here are the dimensions of the different types of SIM cards.
- Full SIM — 85 mm x 53 mm
- Mini SIM — 25 mm x 15 mm
- Micro SIM — 15 mm x 12 mm
- Nano SIM — 12.3 mm x 8.8 mm
- Embedded SIM — 6 mm x 5 mm
If you have an iPhone 5 or newer, your phone uses a Nano SIM. The iPhone 4 and 4S use the larger Micro SIM card.
Samsung Galaxy S4 and S5 phones use Micro SIM cards while the Nano SIM is necessary for Samsung Galaxy S6 and S7 devices.
A Mini SIM card can actually be cut to turn it into a Micro SIM, as long as it’s only the plastic surrounding that’s cut.
Despite differences in size, all SIM cards contain the same types of identifying numbers and information on the small chip. Different cards do contain different amounts of memory space, but this has nothing to do with the physical size of the card.
Where Do I Get a SIM Card?
You can get a SIM card for your phone from the carrier that you subscribe to. This is usually done through customer service.
For example, if you have a Verizon phone and need a Verizon SIM card, you can ask for one in a Verizon store or request a new one online when you add a phone to your account.