What is a SIM Card, and How Does it let You Communicate?

Have you ever wondered how these little chips inside your phone operate and let you communicate with your loved ones? These small cards are called subscriber identity modules, or SIM cards. Without a SIM card, your phone cannot establish a connection with the cellular network and can only be used when connected to wifi.

Let's look at some examples of SIM cards and how they are used today to understand exactly what a SIM card is.

SIM Card

What is a SIM card, and Why is it Necessary?

A SIM card holds your personal information, such as your phone number and other essential elements. A SIM card is transferrable between phones. Hence, if you change your phone, the new phone will inherit all the information and store it. Your SIM carries significant data, including your contacts, text messages, call log information, etc.  

SIM cards are provided mainly by cellular companies that contain essential data like identifying codes and serial numbers. They also contain personal security keys, network authorization data, user identity, and location.

The SIM card also contains two sets of passwords. The first one is a personal unblocking key (PUK) and a personal identification number (PIN).

Types of SIM Cards

As the technology evolved, SIM cards also changed their structure. SIM cards now come in various options and have become increasingly thin and composed of more sophisticated electronics. The different types of SIM cards that evolved include:

Full SIM

This SIM card was developed in the 1990s with a standard dimension of 86x54 mm. These SIM cards are no longer in use. Even though the size was large, the actual working chip only took up a small space. The rest of the structure was made of plastic.


Since full-sized SIMs are no longer used, these SIMs play the role of a standard SIM. It is 25x15 mm, and the contact surface has a large plastic portion.


A micro-SIM is a smaller version of the mini-SIM. It comes with a tiny surface, 15x12 mm. The smaller area is possible because all the plastic is cut off, which leaves behind a card that only has the contact surface.


This SIM is the most miniature form used today. It has an extremely small surface that makes it physically incompatible with older mobiles designed for a micro-SIM. The contact surface of this SIM has dimensions of 12.3x8.8 mm.


eSIMs are also called embedded SIMs since they integrate into the phone's structure. This emerging format is placed directly into the structure of your mobile phone, making it irremovable. Even though eSIMs are not widely used as they are still new, they allow users to change phones without transferring SIM cards.

Are you looking for a SIM card?

SIM cards help you stay connected to your loved ones when you're away. At simify, we provide various options if you plan to take a trip abroad. With easy-to-use technology and affordable prices, our SIM cards are the best thing that helps you stay connected seamlessly throughout your trip.

Thanks for visiting our blog, are you planing to travel to Europe? Check out our range Europe SIM cards before you take off.

Before you take off make sure to check with local government of the travel status.