Mod edit: There's a new site that aims to take some of the guesswork out: http://www.willmyphonework.net/ T-mobile's latest mantra is BYODD: Buy Your Own Damned Device err, Bring Your Own Device. That's great, but which devices can you bring? I was wondering this recently, and had a very difficult time figuring out which phones were and weren't compatible with T-Mobile's network. I couldn't find a nice, clean, comprehensive guide, so I was left to cobble together information from all over the web. My goal here is to consolidate this information in a novice-friendly format for others to use as a resource to be able to tell which phones are and aren't compatible with T-Mobile's network. GSM First of all, you must have a GSM phone. There are several ways to tell if a phone is GSM. If the phone is from T-Mobile or AT&T, then it is GSM. If the phone is referred to as a Global or World phone, then it is GSM. GSM phones are also sometimes called quad-band phones. If you aren't sure, then you can check the phone's specifications. If the phone is GSM, the specifications will list something like "GSM: 850, 900, 1800, 1900 MHz". If it is not, then it will list something like "CDMA: 800, 1900 MHz". Some phones may have both CDMA and GSM in their specifications. These phones are GSM compatible. Having a GSM phone just means that you will be able to make and receive calls on T-Mobile's network. I'm guessing you'll also want to use some data. 3G Let me take a step back. For a phone to work on a network, there are two things that need to happen. First, the phone must support the technology the carrier uses. Then, the phone must support that technology on the frequency the carrier uses. That may sound complicated, but we've already seen it at work. Let's take another look at the specification "GSM: 850, 900, 1800, 1900 MHz". Here, GSM is the technology, and 850, 900, 1800, and 1900MHz are the frequencies the phone supports. T-Mobile uses 1900MHz for their GSM network, so now we can see that since our phone supports the GSM technology on the frequency 1900MHz, our phone is compatible with T-Mobile's network. The technology for 3G is called UMTS. T-Mobile uses two frequencies for their UMTS network: 1900MHz and 1700/2100MHz. So if you check your phone's specifications and see that it has either 1900MHz or 1700/2100MHz listed as one of the UMTS frequencies, then it will support T-Mobile's 3G network. 4G - HSPA+ T-Mobile did a bit of marketing on this one. What T-Mobile calls 4G can more accurately be called HSPA+. This is not really a new technology, rather, it's an upgrade of the 3G technology UMTS. Therefore, if your phone supports the UMTS frequencies 1900MHz or 1700/2100MHz, then we just need to check to see if the phone supports HSPA (slower) or HSPA+ (faster). If it does, then it will be compatible with T-Mobile's 4G network. 4G - LTE This is the 4G technology you're probably more familiar with. Just remember that just because a phone is branded as LTE doesn't mean it will work with T-Mobile. T-Mobile's LTE network runs on the 1700/2100MHz frequencies, and if your phone doesn't support that, then you can't use it on T-Mobile's LTE network. Coverage There is another factor that will determine whether or not your phone will work on T-Mobile, and that's coverage. In order to be able to use T-Mobile's HSPA+ network, you need to be in an HSPA+ area. The same is true of GSM and LTE. T-Mobile has a coverage map available here (for more info on the map, see this post). Currently, LTE coverage is limited to select markets (at least Baltimore, MD; Kansas City, KS; Houston, TX; Las Vegas, NV; Phoenix, AZ; San Jose, CA and Washington D.C.). More will be added as T-Mobile continues to build and grow their LTE network. Summary To summarize, here are the specs you should be looking for when you're trying to determine if a phone will work on T-Mobile's network: GSM: 1900MHz UMTS: 1900MHz or 1700/2100MHz HSPA and HSPA+: Designates phone is capable of faster speeds on UMTS frequencies LTE: 1700/2100MHz (also designated as LTE Band 4 or Band IV) The only specification a phone must have is GSM 1900MHz. If a phone has, for example, GMS 1900MHz and UMTS 1900MHz, then it will still work, but the data will be slower than a phone that is HSPA+ capable, and it will not be able to use the LTE network. Where to find the specs There are several ways to find the specifications for any particular phone. For carrier-branded phones, (e.g. Sprint, Verizon, AT&T) you can check the carrier's website. It will have the technical specifications for the phones they carry, though sometimes it can be difficult to find the specifications relevant for T-Mobile. You can also go to the manufacturer's website (e.g. Samsung, HTC, LG). They will list the full specifications, but sometimes it can be hard to find information on older models. You can also check retail websites like Walmart, Amazon, or Newegg (sorry, gotta plug Newegg. I'm a fan.), but my preferred option is to visit dedicated websites like PhoneArena.com and GSMArena.com. These websites have all of the technical specifications for a wide range of devices. The only caveat here is that sometimes manufacturer's can have several devices with the same name. For example, there are several different versions of the Samsung Galaxy S3, so you'll want to be sure that you are checking the same version of the phone that you are looking to purchase. Other Considerations The spec sheet can tell you if your phone has the hardware to work on T-Mobile's network, but if you are considering using another carrier's device, (e.g. Sprint, Verizon, AT&T) then you may need to take additional steps to configure your phone for T-Mobile's network. Unlocking Cell phone carriers can 'lock' their phones to their network. For example, a 'locked' AT&T phone will only work on AT&T's network, even if the phone meets all of the other requirements above. In order to use a 'locked' phone on T-Mobile's network, the phone will need to be 'unlocked' first. You will need to contact the original carrier in order to have your phone unlocked, and under current US law, it is the carriers discretion as to whether or not to grant the request. Configuring your phone for T-Mobile Once your phone is unlocked, it may need to be reconfigured to work on T-Mobile's network. Fortunately, this is not something you have to do on your own. If you take your phone into a T-Mobile store, or call T-Mobile's support line, they will be able to help you get your phone configured for T-Mobile's network. If you want to do it yourself, you can also post a question to your phone's forum on this site and someone might be able to help you with the configuration. Still have questions? If you still have questions, don't feel bad. It can be difficult to tell whether or not your phone is T-Mobile-ready. If you are uncertain, you can ask at a T-Mobile store, or call T-Mobile's support line. They might be able to help you determine if your phone will work on T-Mobile's network. My suspicion is that though they may tell you a compatible phone isn't, they are unlikely to tell you a non-compatible phone is. If you have any questions or concerns, you can also post a question to either the phone's forum or this T-Mobile forum and someone will be able to help you determine if your phone is compatible. Frequency Bands Unfortunately, there are a lot of different ways to say the same thing. You've heard me talk about the 1900MHz and 1700/2100MHz frequency bands, but these frequencies can be described in different ways. 1900MHz is also known as the PCS band. The combination of 1700 and 2100MHz frequencies is also known as the AWS band. For LTE applications, the AWS band is also known as LTE Band IV. It's important to note that there is a difference between a phone that supports the 1700 and 2100MHz frequencies independently (e.g. UMTS: 1700MHz, 2100MHz) vs collectively (e.g. UMTS: 1700/2100MHz) The latter is the designation for the AWS band, and is what is required for T-Mobile compatibility. Please let me know if you have any feedback. Thanks!