What Is a GSM SIM Card?

A Global System for Mobile Communication Subscriber Identity Module, or GSM SIM card, is a SIM card that uses the GSM network. Having this card in an unlocked cell phone while using the correct frequency allows a cell phone user to use his cell phone in various countries all over the world. The GSM network is the network used by most countries in the world, allowing cell phone users to carry their phones from country to country. This network is not the primary network used in countries such as the United States, which is why many US residents have trouble using their phones overseas.

To use a GSM SIM card, a user will need an unlocked phone—that is, a phone that is able to use SIM cards from different phone carriers—that uses the GSM network and works at the frequency the destination country uses. In many European countries, that frequency is 900 MHz or 1800 MHz. A phone that uses the proper frequency is important because even if a phone can use the GSM network, if it is not on the correct frequency, it still won’t work. Once a user has an unlocked phone that will work with the GSM network as well as the correct frequency, he can use the GSM SIM card. This card allows the user to use the same phone number internationally, no matter which country he is in.

Having a GSM SIM card allows a person to use the same cell phone in different countries rather than having to buy a new SIM card or phone whenever they travel internationally. This is ideal for those who travel often or want to be able to use their phone while on vacation. Since the SIM card holds the user’s phone number and information, the chip can even be used on another person’s international phone, while still billing the owner of the SIM card. This allows a person to either buy a phone of his own or rent one from an appropriate carrier.

If a person does not have the appropriate phone for a GSM SIM card, it is possible to rent an international phone. This is possible because he can insert the chip in various phones and use them in different countries. The information stays with the SIM card so the user can simply pay a fee to use a compatible phone of his choice while traveling in a different country. This allows him to use the phone without paying his domestic carrier’s roaming charges. Renting a phone allows someone to get a phone when they do not wish to or are unable to use his phone overseas.

To understand GSM phones and SIM cards, you need to know more about mobile networks. When you see numbers like 4G and 5G, the "G" simply stands for "generation." That means 5G is the fifth-generation mobile network, 4G is the fourth generation network and so on.

Each generation network uses a different technology standard. Introduced in 2019, 5G uses New Radio. Its predecessor 4G was implemented in 2009 and uses Long-Term Evolution tech — hence the 4G LTE designation. Before these two networks existed, 3G was deployed in 2001 and 2G rolled out in 1991. The key technologies for 3G were WCDMA and CDMA2000. Meanwhile, 2G ran on GSM, D-AMPS and IS-95.

All this may seem a bit like alphabet soup, but the key point is this: Cellular technologies have evolved dramatically over time. It's mindblowing to consider that the first generation cellular network went live in 1979. But we're now looking at 5G access in most of the United States, especially with the big three cellphone companies rolling it out in most states and major metro areas.

So if both 5G and 4G LTE are widely available, why do we need 3G or 2G? The answer to that is a bit complex. Traditionally, GSM and CDMA provide cellular service when there's no 4G LTE or 5G coverage. These technologies originated from 2G and 3G networks. However, most cellphone providers plan to phase out 3G in 2022. This will impact 3G phones, along with medical and home security systems still on 3G. As for 2G, the last carrier that has it is T-Mobile. But don't expect to get new 2G service for long — T-Mobile plans to pull the plug in December 2022.

With 3G and 2G going dark, the whole question of whether GSM phones have SIM cards may become irrelevant. However, some people may need access in the meantime. Back when GSM and CDMA were the only games in town, there was an easy way to tell the two apart: GSM phones had SIM card slots, while CDMA devices did not. Today's 4G and 5G smartphones also use SIM cards.

Since 2G and 3G networks are being decommissioned, you may find it difficult to track down a GSM SIM card. After all, 4G and 5G services are expanding coverage across the country. Nevertheless, you can find a GSM SIM card if you look hard enough. Some are available for as little as $2 per card. Most GSM SIM cards cost under $10. You may find them for GPS tracking, older smartwatches and other devices. Some come bundled with prepaid service, but you'll likely pay between $30 and $60 for these cards.

People have used a few methods to close SIM cards. However, the most straightforward way to accomplish this feat is with a SIM card cloning device. You may also see card reader/writer/programmer devices, cloner/backup devices or similar labels, mostly as USB-connected devices. To make sure you know what you're getting, do a little bit of research and read product descriptions carefully before you buy.

The basic process of cloning a SIM card involves copying its data and writing it to a new card. You'll need one of these reader/writer devices plus a blank programmable SIM card. You'll also need SIM card data cloning software. Some apps let you create usable SIM cards, while others only clone SIMs for forensic purposes so you can see the phone user's data. Read app descriptions thoroughly before downloading. If you're cloning a SIM for use, you'll need a USB SIM card reader app as well.