This came up at work the other day. It's sort of important to know for things like testing, or even how many test devices to get on different operators.
The refrain I heard is "there are hundreds of carriers, but almost everyone is on the top four." Well, sorta.
First: Carrier is what we call them in the US. Operator is more an international term. They mean the same thing. But both are a bit fuzzy. They probably are best defined for the most part as "whoever's name is on the bill you get/card you buy."
But that's not important. Most of the many hundreds of operators are MVNOs. Mobile Virtual Network Operators, that ride entirely on top of the other networks, which are run by MNOs (you guessed it, Mobile Network Operators). Virgin Mobile, for example is just a brand of Sprint, with no technology difference, at all. If it works on Sprint, it works on Virgin.
The only MNOs in the US are:
- Verizon Wireless - 108 mm
- AT&T Mobility - 108 mm
- Sprint Nextel - 55 mm
- T-Mobile USA (T-Mobile is a German company) - 34 mm
- Metro PCS - 10 mm
- Leap Wireless (Almost entirely branded as Cricket) - 6 mm
- US Cellular - 6 mm
The above sizes MAY not represent all the MVNOs under each operator. It's sometimes hard to tell what they are counting, so there may be mismatches. You don't, generally, need to worry about MVNOs. Testing on the basic network is enough.
If your app is more important in a specific region, you may also find some of these percentages are skewed. US Cellular, for example, has a big footprint in the central plains, and just a few markets in other parts of the country. If your product is big in Chicago, you might need to test on that, but not if it's big in LA.
If you don't want to buy a bunch of phones on each of the top 4-5 operators, I am pretty sure Device Anywhere covers most/all MNOs so that may be an option to save money. Not that Device Anywhere is exactly cheap itself.
Also: I left out Clearwire. Technically an MNO but of no significance because they sell no handsets directly. When you see this, pretend it says "Sprint." Look it up or ask if you don't get it.