Inserting a GSM sim into a mobile device

GSM vs. CDMA – What’s The Difference?

You may be a casual user of any carrier connected mobile device – that’s one which uses a SIM card. But then you likely have not noticed that some devices or networks are labelled as GMS, and some as CDMA.

Whether you have noticed or not, you probably wonder what the differences between the two are. This knowledge alone may very likely affect your choice of device or network provider. So here we dive right into to the thick of things.

The Basic Timeline

GSM has been around since the early 1980s. That is when a European consortium set about standardizing future mobile communication technology. The technology was already well established when, in 1995, computer chip makers Qualcomm created the new, faster, CDMA standard.

Comparing the Two

Interestingly enough, GSM devices are programmed to use their own network, while CDMA phones use another system entirely. You must therefore make a choice on which side of the fence you want to live, even if only temporarily.


GSM is a global standard in almost all locations, including outside the US. These devices operate via SIM cards which store your phone number and basic data on it. In this system, unlocked GSM devices are likely compatible with the networks in the GSM system.


CDMA on the other hand, has only a handful of networks worldwide that use its technology. It does not use the SIM card system, although they are including them more commonly due to 4G network requiring it. Rather than the information being stored on the SIM as with GSM technology, it is located on the carrier’s network. Therefore, to switch between networks or devices, the company must be contacted and must manually approve the switch.

How Even is the Battle?

GSM stands for Global System for Mobiles and CDMA is for Code Division Multiple Access. They are both different radio systems with which mobile devices connect to their service.

With four major companies offering wireless phone services today, it is seemingly split equally with 2 networks in each category. Sprint and Verizon are CDMA while AT&T and T-Mobile use GSM. Yet it is anything but an even battle.

The more popular of the two is GSM, mainly due to it being widespread across the globe. Some countries made it the law that all providers must use it.

See the Details

AT&T & T-Mobile Sprint & Verizon
CompatibilityWorldwideUnited States

Customer Information & Number
Is stored on SIM card Is stored on the Networks database
Switching Companies Transfer plans and get the company’s SIM card. You may use any unlocked device that is GSM compatible. Transfer plans and get the company’s SIM card. Must use their branded devices.
Switching Phones Insert SIM card into GSM device and it will host your number.
GSM networks must accept all GSM compatible devices.
1 – Carrier must agree to the switch and perform it.
2 – CDMA networks are very  specific in which devices they allow. Often limited to devices they sell.

But Why Does it Matter to Me?

Beach bag and hat lying on the beach

In terms of the way you use your cell phone or tablet, not a lot, actually. The differences are pretty much invisible in everyday use. Yet it can be quite significant when it comes to choosing your network provider and even the device you use.

If you don’t travel much and plan to stick with one company and the phone they sell you, then things are simple. You can go with GSM or CDMA and you will be equally satisfied. However, if you like to shop around for deals or travel often, then GSM is the way to go.

Reasons GSM is More Versatile

Well, firstly there is no headache at all to switch between devices. You may switch them weekly and your service will never be interrupted. Your most contacted friends and family will never know the difference. In addition, there is a much bigger selection of GSM devices then CDMA. Therefore, you will have much more a variety that you can pick between.

Secondly, most of us travel and we do that often. In fact, it is extremely common to cross over into another country or continent.

Someone inserting a SIM card into a SIM card slot on a mobile device

Should you be thinking about taking your smartphone abroad, a CDMA device is unlikely to work when you get to your destination. You would then need to have a second phone that would be solely for travelling. The main reason for that is because of the way that CDMA works. They do not use SIM card technology but rather program their networks system to know that this device belongs to this person with this number. Therefore, you will need to get yourself a new number as well as device that is compatible with the GSM worldwide system of SIM cards.

Take a GSM phone to almost any country in the world, however. You can simply pop a local SIM in (or use your regular SIM and accept the roaming charges) and away you go. Or, you can buy yourself a Dual-SIM mobile phone and use it for travelling. To find out more about Dual-SIM system, check out ‘How Do Dual SIM Cards Work’.

GSM vs. CDMA – SIM Cards Synopsis

The difference is that GSM phones, as mentioned, use SIM cards as they are easy to replace or removed and put into a different device. CDMA devices don’t have SIM cards. Instead, they rely on a phone number, user and contact information held at the network end. When it connects to a network, the information is checked against the phone. This makes the device more secure and able to be entirely deactivated remotely. Yet it also means several hoops must be jumped through if you ever want to switch networks. It also means that, if you do switch, it can only be to another CDMA network. You will also need the assistance of the carrier to make the move.

Which Providers Use Which Networks?

Among the big 4 US networks, GSM is used by AT&T and T-Mobile, and CDMA is used by Verizon and Sprint. This makes the split roughly 50/50 in terms of connections. But, it also makes the devices used by many US citizens incompatible with the rest of the world.

Sub-Networks as Another Option

Please note: We are not responsible for any adjustments in regards to the following networks. Please confirm the information is up to date before deciding on a mobile device or network.

United States

Main NetworksSub Networks
GSMAT&TAirVoice Wireless, Black Wireless, Boom Mobile, campusSIMs, Consumer Cellular, Cricket Wireless, EasyGO Wireless, good2GO Mobile, H2O Wireless, Jolt Mobile, Net10 Wireless, Pix Wireless, Puretalk USA, Red Pocket Mobile, Straight Talk, TracFone
GSMT-Mob ile Consumer Cellular, EcoMobile, GoSmart, Hayai Mobile, Jaguar Mobile, Jolt Mobile, KidsConnect, Liberty Wireless, MetroPCS, Mint Sim, Net10 Wireless, Red Pocket Mobile, Republic Wireless, Simple Mobile, Speed Talk Mobile, Straight Talk, Telcel America -Tempo Telecom, The People’s Operator USA, Ting, TracFone, Ultra Mobile, Univision Mobile, US Mobile, Walmart Family Mobile, ZingPCS, Zip SIM
Affinity Cellular, Armed Force Mobile, Boom Mobile, Credo, Eco Mobile, Expo Mobile, Net10 Wireless, Page Plus Cellular, Puppy Wireless, Red Pocket Mobile, ROK Mobile, Selectel Wireless, Straight Talk, Total Wireless, TracFone, Zing PCS
Boost Mobile, FreedomPop, Net10, Pix Wireless, Project Fi, Red Pocket, ROK Mobile, Straight Talk, Tello, TextNow, The People’s Operator, Ting, Trac-Phone, Twigby, Virgin Mobile

As you can see from the above list, there are various networks that will use multiple of the 4 main carriers. Straight Talk and Trac-Phone are two examples that will use any of the 4 networks, depending on your preference.


Approximately 90% of Canadian mobile phone users subscribe to one of the three largest national telecommunication companies. They are Rogers Wireless, Bell Mobility, and Telus Mobility, or one of their subsidiary brands.

Main NetworksSub-Networks
HSPA+, LTE (GSM) Rogers Communication Rogers Wireless, Fido Solutions, Chatr Mobile
HSPA+, LTE (GSM, CDMA) BCE Inc. Bell Mobility, Virgin Mobile, Bell MTS, Lucky Mobile
HSPA+, LTE (GSM, CDMA) Telus Corporation Telus Mobility, Koodo Mobile, Public Mobile
HSPA+, LTE (GSM) Vidéotron Vidéotron Mobile

A Bit Of History

Back in the early 1980s, JVC and Sony were at war over who had the best video recording format. That is because they both developed their own systems at around the same time. It meant recordings made on a VHS machine couldn’t be played on a Betamax machine and vice versa. Although it hasn’t ended in a war of formats in the same way, GSM and CDMA technological differences have resulted in a very similar situation. Devices designed for one network aren’t able to be used on the other.

Why Don’t They All Just Use GSM?

A good question, and one with an answer that is encased in financial resource and commitment.

When CDMA was first released in the mid-90s, Verizon, Sprint and US Cellular jumped on board. It was mainly due to faster speeds, greater usable bandwidth for calls and texts, and increased security. Because we are talking about huge businesses with billions of dollars invested in their networks, switching isn’t quite so easy. Also, because Verizon are the largest single mobile network provider in the country, they have the resources and support to carry on going it alone. Sprint are in a similar position, where the number of connections they have is sufficient to support sticking with CDMA. They also have enough influence with cell phone device manufacturers to have devices made especially for them.

GSM speeds actually passed those of CDMA some years ago. But, with the money already invested in CDMA, Verizon and Sprint decided to persevere. A number of networks, including Bell and Telus in Canada, have changed to GSM from CDMA. Yet the financial considerations are greater than the technical ones for large networks.

Where Does 4G Fit In?

4G uses a system called as Long Term Evolution (LTE) technology.

If you have a 4G device on Verizon or Sprint, you’ll no doubt have noticed that the device does indeed have a SIM card. This is because the 4G LTE standard calls for the use of SIM cards and, without them, the manufacturers and networks couldn’t call their devices 4G. Despite having a SIM card, devices on Verizon and Sprint are still CDMA devices, and subject to the same restrictions of older, non-4G devices. Verizon, for example, still uses CDMA to transmit phone calls, making their devices incompatible with any other network although they are committed to changing this.

So Which Network To Choose?

Assuming you have no need for the data transmission speeds brought by 4G – and the often premium price it carries – and if all you need is phone, text and the occasional bit of browser use, GSM and CDMA are the far more cost effective option.

Given the global advantages, and if all other factors are equal, we’d say choose a GSM network-compatible device if only to reduce potential problems when travelling or when switching networks in the future. Over time, GSM is highly likely to be the last man standing as both Verizon and Sprint will inevitably succumb to the pressure to switch. If you are one of those people for whom changing your mobile device is only a very occasional thing, going with GSM is also likely to mean you don’t face the problem of your phone suddenly becoming a new paperweight.

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