What Is GSM in Cellular Networking?

GSM is short for Global System for Mobile Communications

GSM (pronounced gee-ess-em) is the most popular cell phone standard, and is used internationally, so you've probably heard about it in the context of GSM phones and GSM networks, especially when compared to CDMA.

GSM Logo

GSM originally stood for Groupe Spécial Mobile but now means Global System for Mobile communications.

According to the GSM Association (GSMA), which represents the interests of the worldwide mobile communications industry, it's approximated that 80% of the world uses GSM technology when placing wireless calls.

Which Networks Are GSM?

Here's a quick breakdown of just a few mobile carriers and which use GSM or CDMA:


  • T-Mobile
  • AT&T
  • Indigo Wireless
  • Pine Cellular
  • TerreStar

UnlockedShop has a more comprehensive list of GSM networks in the US.


  • Sprint
  • Verizon Wireless
  • Virgin Mobile


For practical and everyday purposes, GSM offers users wider international roaming capabilities than other US network technologies and can enable a cell phone to be a “world phone." What's more, things like easily swapping phones and using data while on a call is supported with GSM networks but not CDMA.

GSM carriers have roaming contracts with other GSM carriers and typically cover rural areas more completely than competing CDMA carriers, and often without roaming charges.

GSM also has the advantage of easily swappable SIM cards. GSM phones use the SIM card to store your (the subscriber's) information like your phone number and other data that proves you are in fact a subscriber to that carrier.

This means you can put the SIM card into any GSM phone to instantly continue using it on the network with all your previous subscription information (like your number) to make phone calls, text, etc.

With CDMA phones, however, the SIM card does not store such information. Your identity is tied to the CDMA network and not the phone. This means swapping CDMA SIM cards doesn't "activate" the device in the same way. You instead need approval from the carrier before you can activate/swap devices.

For example, if you're a T-Mobile user, you could use an AT&T phone on the T-Mobile network (or vice versa) so long as you put the T-Mobile phone's SIM card into the AT&T device. This is super useful if your GSM phone is broken or you want to try out a friend's phone.

Keep in mind, however, that this is only true for GSM phones on the GSM network. CDMA is not the same.

Something else to consider when comparing CDMA and GSM is that all GSM networks support making phone calls while using data. This means you can be out and about on a phone call but still use your navigation map or browse the internet. Such capability is not supported on most CDMA networks.

See our explanation of CDMA for some other details on the differences between these standards.

More Information on GSM

The origins of GSM can be traced back to 1982 when the Groupe Spécial Mobile (GSM) was created by the European Conference of Postal and Telecommunications Administrations (CEPT) for the purpose of designing a pan-European mobile technology.

GSM didn't begin being used commercially until 1991, where it was built using TDMA technology.

GSM provides standard features like phone call encryption, data networking, caller ID, call forwarding, call waiting, SMS, and conferencing.

This cell phone technology works in the 1900 MHz band in the US and the 900 MHz band in Europe and Asia. Data is compressed and digitized, and then sent through a channel with two other data streams, each using their own slot.