What Is A SIM Card?

Date First Published: 25th October 2023

Topic: Computer Systems

Subtopic: Computer Hardware

Article Type: Computer Terms & Definitions

Difficulty Level: 5/10

Learn about what a SIM card is in this article.

Stands for a Subscriber Identification Module card. A SIM card is a small, removable card that contains a computer chip which stores identifying information about a mobile device owner, including the phone number and the mobile carrier. This allows the phone to connect to the mobile carrier network to make and receive phone calls, send and receive text messages, and access mobile data.

Sizes

SIM cards come in three sizes, including:

• Full size - 85.6 x 53.98 mm x 0.76 mm
• Mini-SIM - 25 x 15 mm x 0.76 mm
• Micro-SIM - 15 x 12 mm x 0.76 mm
• Nano-SIM - 12.3 x 8.8 mm x 0.67 mm

Over the years, SIM cards have got smaller since they were first introduced in 1991. Most users don't need to worry about these sizes because nearly all phone companies are using nano-SIM. But, users with an old SIM card that is standard or macro size may need to have it replaced by the carrier to fit it into new devices or cut it down to size.

What Is An eSIM Card?

An eSIM card is a pre-installed computer chip embedded inside a phone. It works in exactly the same way as a SIM card, but it is not a physical SIM card, so users can connect to a mobile carrier network without needing to insert a SIM card. This means that users do not need to worry about the size of the SIM card or it falling out of the phone. eSIM cards are considered more reliable and secure than physical SIM cards.

Can SIM Cards Be Transferred?

Since SIM cards store small amounts of information, like contacts, this makes them useful for transferring the cell phone service and all the data to another device. The carrier will still be able to identify the user as well. To protect a SIM card from being used by others for making phone calls, sending text messages, or using mobile data, a SIM PIN can be used, which will ask for a password or a passcode when it is used on another device or when the device is restarted.

How To Remove Or Replace A SIM Card?

The process of removing or replacing a SIM card varies, depending on the device. Some devices, like iPhones have a SIM card tray that pops our from the side of the device. The tray can be opened by pressing the hole with a paperclip.

Other devices might store the SIM card behind the battery, which is only accessible at the back panel. The SIM card can be removed and replaced without the need to power down the device.

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