The iPhone XS and XS Max sold in the US will be the first model in years where every unit sold will work on all four US carriers: AT&T, Sprint, T-Mobile and Verizon. For a few years now, AT&T- and T-Mobile-branded iPhones haven't worked on Sprint and Verizon, but this year, the phones will be cross-compatible.

Around the world, compatibility will vary. There are four different models of the iPhone XS and XS Max being sold in different countries, and they have slightly different LTE band support. That means they'll all work at least somewhat around the world, but you want to have your local model for the best LTE coverage. Here's how they break down.

My information comes from Apple's official LTE support page. I've heard that some other pages on the Apple site are giving slightly different information, which is typical in the first day or two of an iPhone release. For instance, the European sales pages appear to show model A1920, while the LTE support page says (I think correctly) that Europe is getting model A2097. It'll all shake out in a week or two; for now, here's what we've got:

US and Canada

The US and Canada get models A1920 (XS) and A1921 (XS Max.) Those models have T-Mobile's new Band 71, which extends T-Mobile's LTE coverage in suburban and rural areas. They do not have LTE bands 11, 21, or 28.

Japan, China, Hong Kong, and Macau

Japan gets models A2098 (XS) and A2102 (XS Max.) Those models remove bands 32 and 71 and replace them with bands 11, 21, and 28. They also presumably support Japan's SUICA contactless payment platform.

China gets models A2100 (XS) and A2104 (XS Max.) I can't figure out right now how the A2100 is different from the US A1920 model. The 2104 has two physical SIM slots rather than the other models' one-SIM, one-eSIM setup.

Hong Kong and Macau get models A1920 and A2104, just for giggles.

Everywhere Else

The rest of the world gets models A2097 (XS) and A2101 (XS Max.) Those remove band 71 from the US model and add band 28; they do not have bands 11 or 21. They keep band 32.

Who Uses Which Band?

The good news is, none of the bands being swapped around here are carriers' primary frequencies. All of the iPhones will work on bands like 1, 2, 3, 4, 5, and 7, which are the ones most carriers in the world use to establish basic LTE coverage. All of them, as far as we know right now, will make both GSM and CDMA voice calls. (I think A2097 and A2101 might not support CDMA, but I have no proof of this.)

Band 28 is used as a supplementary coverage band by carriers in Australia and New Zealand, France, Finland, Iceland, Germany, the Philippines, Singapore, and Taiwan, Nigeria, and a bunch of South American countries. If you're in one of those countries and on an operator that uses 28 (like Free in France), you'll get poorer coverage with a US/Canada iPhone than with a European/Asian model.

Bands 11 and 21 are Japan-only bands. You need them in Japan. You don't need them anywhere else.

Band 32 is a supplemental downlink band that's starting to be used in Europe. It really speeds up connections there.

There may also be some surprises in the ways the various models aggregate frequency bands, which could speed them up or slow them down in various countries. Aggregation combines lanes of frequency into faster, wider lanes. It could be that one model of the phone supports aggregating 3/7/28 (which is needed in Australia) and the other one supports 2/4/7C (which is awesome in Canada). We just don't know yet. For now, to be safe, don't get any bright ideas about importing iPhones.

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