SIM cards shouldn’t sound like an unfamiliar term to you since they’ve been around for a while. Precisely, since the days of the first slightly-modern but still bulky phones, flip phones, and phones with a slider. Remember those? You should appreciate having an ultra-thin Samsung or Huawei Android device even more. First of all, if you aren’t tech savvy, let us clarify. SIM cards look like a small, thin rectangle made of plastic that used to be inserted into your phone.
And when we say into – we mean taking the back cover off, usually removing the battery, and finally reaching a spot where you’d be able to insert it. Luckily, that practice has changed drastically, and we’ll tell you more about it after we explain what is a SIM card, in fact.
What are the Functions of a SIM Card?
First of all, even though many of us don’t know, and don’t really need to know, SIM stands for Subscriber Identity Module. You’ll find why exactly it has that name in just a second. A SIM card is mandatory if you’d like to contact your friends via a text or multimedia message, as well as call them and leave voicemails. It allows you to have a phone number that’s personalized to you, and people you share it with can get in touch with you.
Apart from that, it can hold a limited amount of data, since it’s limited to about 64KB of memory which is actually more than it looks. SIM card essentially connects you to a network of signal-carrier towers in your city/village. Since the towers are everywhere and on a standardized distance, you’ll have a maximum signal unless you’re somewhere desolate.
You can read more functions of a SIM card in our newer article.
Can I use my SIM card with other smartphones?
The card allows you to save people’s names, home, work, and mobile numbers, as well as their e-mails instead of using your phone’s memory for that. If anything happens to your device, or your screen gets cracked, by transferring your SIM card to another phone you’ll quickly find your contacts are intact, and you won’t have to deal with awkward conversations.
That’s a saving grace if you’re in a tight spot, but your phone’s battery juice is all drained up. Just transfer it to a friend’s phone, and you can put your Mom or Dad’s mind at ease.
Is SIM card necessary for the phone to work?
Is the SIM card actually necessary? Can a phone function without it? The answer depends on what exactly do you want from your phone. If it’s accessing internal or external (SD card) memory, or even connect to your home wireless Internet, then yes, you’ll have no problem with that. Same goes for playing mobile phone games and other multimedia that requires no phone number confirmation to provide service.
However, if you thought that having no SIM card can still enable services like Viber or WhatsApp to work via the Internet, you were wrong. They require your phone number to register your account, and the account is tied to the phone number after that.
What are the Types of SIM Cards?
| SIM Card Type | Description | Size | Common Usage |
|---|---|---|---|
| Full-Size SIM | The biggest form of SIM card available to the consumers. | 8.5cm x 5.4cm | Less common, mostly used in older devices. |
| Mini-SIM | A standard SIM card that is very common when you buy one from a retailer which can then be broken down to be smaller. | 25mm x 15mm | Used in older smartphones without hybrid slots or water-resistant capabilities. |
| Micro-SIM | The smaller version of Mini-SIM with the same design and contacts, reduced length and width. | 15mm x 12mm | Introduced in 2010, used in older smartphones. |
| Nano-SIM | The most common SIM card size used today on smartphones, tablets, etc. | 12.3mm x 8.8mm | Widely used in current smartphones, saves space for other components. |
| eSIM | Embedded SIM technology, no physical card required. SIM details can be remotely provisioned and managed. | No physical size | Used in newer smartphones, smartwatches, and other connected devices. |
| Prepaid SIM | A SIM card type that can be recharged whenever you want to enjoy the service. | Varies | Common for temporary or disposable needs, travel, or budget-conscious users. |
| Postpaid SIM | Requires signing a contract with a provider. Monthly payments cover services like calls, SMS, and data. | Varies | For long-term phone service plans with added benefits and features. |
While SIM cards are in use for a long time, it doesn’t mean they didn’t go through a process of overhaul and upgrade. The biggest change, definitely, is the size. In the past, mini-SIM cards were the norm and were inserted in a way we mentioned above. But with a tendency to make things in a smartphone, and the phone itself, thinner, lighter and sometimes smaller – new forms arose.
Full-size SIM
Full-Size SIM Card is the biggest form of a SIM card – in size of a credit card, around 8.5cm x 5.4cm. Phone service providers still sometimes supply the full-sized SIM, but with cut-outs for all the smaller sizes. Typically, your PIN and PUK codes are written on it, as well as the phone number you’ll be using, which comes in handy until you remember it.
Mini-SIM
Mini-SIM is still in use, but only on the older models of smartphones that don’t have a hybrid slot, or don’t possess waterproof and water-resistant capabilities so the back panel can be opened. It’s recognized as a standard SIM card today, and you’ll easily recognize it for its rectangle with one corner cut-off design, and golden-looking contacts on one side.
Micro-SIM
Micro-SIM boasts the same look as Mini-SIM, and the contacts are identical, however, it has a reduced length and width, while the thickness is still the same. The trend of smartphones using it started back in 2010 with iPhone 4 being the first, and they became even smaller since then, which leads us to the next one.
Nano-SIM
If you thought SIM cards wouldn’t get smaller than micro, which sounded small already, you were wrong. It’s basically the side of the golden contact, without too much surrounding plastic to fill the space. It’s great news for smartphones today since it saves space and is usually plugged via a hybrid SIM slot, along with either a second Micro or Nano SIM, or an SD card. If you’re wondering how small can SIM cards become, get this – they had to add a small rim of insulating plastic only to prevent short circuits, the golden contact is all you actually need!
Embedded-SIM
Embedded-SIM is a form not widespread and in use only in Google Pixel 2 and the newest electric cars, it’s basically a SIM chip soldered onto the board itself, so you don’t have to insert it yourself. Maybe we’ll start using this type in the future, but for now, micro-SIM and nano-SIM are the most commonly used.
Prepaid and postpaid SIM cards
Judging by the name, it should already be pretty obvious, but here it is: Prepaid SIM cards, or sometimes called burner cards, allow you to get a phone number for yourself, and then buy credits so you can text, call, or use the Internet. When credits run out, you’ll have to refill them to regain those functions.
Postpaid SIM cards, on the other hands, require you to go to the provider, sign a contract for 12 or 24 months and choose a package that fits your needs. Then, you’ll have to pay the basic price of that package per month, which gives you perks like a certain number of free SMS, calls, or mobile data.
SIM Card FAQs
Primarily, a SIM card has two functions. Firstly, it provides a unique identification number, which can be used to make calls and surf the Internet using data plans. Secondly, it allows for storing information such as contacts and messages. As technology progresses, the usage of SIM cards might also change, but these are the 2 important uses of a SIM card.
A sim card works by making a connection to the nearest mobile tower with information such as IMSI, authentication keys, and network-specific data. The mobile network then uses this information to verify the identity of the request and fulfill it, allowing you to make calls or browse the Internet.
You cannot use a mobile network with a SIM card provided by another company. If you want to switch networks, you should purchase a new SIM card from the new operator.
During international travel, you can still use your SIM card if it supports it. Keep in mind that, not all SIM cards support this feature. So you should make sure that your SIM card has this feature built in before purchasing one.
Conclusion
Do you need a SIM card? We meet people that live their life without social media or popular messaging applications, but a phone number is another thing. You’ll honestly have a hard time finding a job in your city, staying in contact with your friends, or meeting and exchanging contacts with new people you meet. Sure, it’s not as bad as it once was, since you can use Wi-Fi pretty much everywhere you go, and call, text, and video call via Skype and similar services, but you’d still get weird looks from people when they hear you don’t have a phone number.