Phone Deal Finder
Plan Finder

What Is A Sim Check?

SIM cards are arguably the most important piece of hardware in your phone, giving you a phone number and tying your identity to the device. Everything from modern smartphones to decades-old flip phones needs a SIM card if you want to be able to call and text people on a mobile network.

Because SIM cards are so important to the proper activation and operation of our phones, everyone needs to make sure that their SIM cards are working properly. A faulty SIM card could render your phone functionally useless.

How Do SIM Cards Work?

Your SIM card acts as the brain of your phone by tying your identity to the device through a phone number and your carrier. Your individualized SIM card allows you to call and text others. All phones have some kind of SIM card, whether they be an old-school flip phone or cutting-edge smartphone.

Modern smartphones can still function at some level without a SIM card. Many of them can still connect to the internet and use applications. However, it is the SIM card that allows you to connect to a mobile network and gives you the capacity to communicate on that network. That is why any phone made in the last few decades has to have a SIM card, no matter how advanced it is.

The different types of SIM cards are called GSM (Global System for Mobile communication) and CDMA (Code Division Multiple Access).

GSM technology involves a physical SIM card that you can remove and put in a new phone, retaining your existing mobile identity despite the device change.

CDMA involves having a virtual electronic serial number that is tied to the phone. This is much more difficult to change as the phone is explicitly tied to the carrier directly.

What Types of SIM Cards are There?

While the function of SIM cards has been universal since their creation, there are multiple different types of SIM cards. As technology has evolved, so has the way we use SIM cards to connect to our mobile networks.

Traditional SIM Cards

Traditional SIM cards are a card inside of your phone that store personal info that makes that phone unique. It connects you to your network, and often it will also store your contacts, making a switch from one cell phone to the next relatively painless.

When switching between carriers, you cannot keep your original SIM card. However, you can work with your new carrier to try and have your phone number preserved during the transition so that you can continue using it.

Many phones today also offer cloud storage capabilities that let you save your phone’s info online from being immediately copied onto your new phone at your leisure.

eSIM Cards

An eSIM card is writable, meaning you can alter the information on them. This allows you to switch between carriers without having to replace any hardware. All you have to do is connect to the Wifi and complete the upload or rewrite process online. These SIM cards are embedded in your phone and are not meant to be removed.

This is necessary because eSIM cards are not removable in the first place. This could be a knock against them for people who prefer to have the option of removing them. This technology does allow for dual SIM phones with two phone numbers to exist.

As of this time, many phones have not converted to eSIM, but it is a quickly growing technology that is used in some of the best devices on the market.

How To See Your SIM Card Number?

Our SIM card number isn’t something that most people think about often, but it can be very important to know and be able to access. When registering your phone, changing your phone number, or for other verification reasons, you may be asked to provide your SIM card number in order to receive services.

It is also useful to have your SIM card in the case of theft. With your SIM card, you can identify your ICCID so that your phone can potentially be tracked. Your SIM card is a great way to identify your phone when you don’t physically have it on hand, and it will be the most important piece of information you have if it is stolen.

The process for figuring out your SIM number is similar in both Android and Apple.

How To Check Your SIM Number on Your iPhone?

  1. Open the settings menu.
  2. Click the ‘General’ tab.
  3. Click ‘About.’
  4. Scroll down until you see ‘ICCID,’ which should have the serial number next to it.

If you can physically remove your SIM card, check to make sure that the numbers match up. The last six digits of the SIM number on the card and the ICCID number provided should be identical.

How To Check Your SIM Number on Your Android?

  1. Open the settings menu.
  2. Scroll down and click on the ‘About’ tab.
  3. Click ‘Status’ and then tap ‘IMEI Information.’
  4. The SIM card will show either your IMSI number or ICCID number.

Just like with the iPhone, it is best practice to check the physical card if this is an option for you.

How To Make Sure Your SIM Card is Working Properly?

The easiest way to make sure your SIM card is working is to try making a call or texting somebody. If the call or message goes through, then that means the SIM card is connected to your mobile carrier, and no further action is needed.

If it does not go through, check your network connection. If your phone says no carrier or network could be detected, then your issue is either on the carrier’s end or with your SIM card.

If your SIM card isn’t working, then the best practice is to contact your carrier at their local branch. Your carrier should be able to either assist you in fixing the SIM card or provide you with new hardware that doesn’t have these issues.


It is important to know how your SIM card works, given how important it is to the functioning of your phone. Even if you aren’t having any phone issues, it is worth it to record your SIM number, as it can help with identity verification and could be vital in finding your phone if it is stolen. No matter what type of phone you have, your ability to connect to your network and use your phone properly relies on your SIM card.

Want the best deal on a new phone or plan?
Search Deals