Depending where you live, you’ll now be able to text 9-1-1 from your cellphone if you for some reason you can’t make that emergency phone call when you need it. The program is rolling out in certain areas now, with expansion to the rest of the country planned by the end of the year.

The Federal Communications Commission has a guide on how to text 9-1-1 — but it will only work for customers on AT&T, Sprint, Verizon and T-Mobile as of now. Basically, if you can, call first. And if you get a bounceback text message saying that your text didn’t work, well, you’ll need to find a way to call.

If you have an emergency and live in one of these areas currently served by the program, you can send a message with your physical location and emergency to 9-1-1. The location is especially important as dispatchers can’t tell your location from a cellphone call.

Eventually, photos will also be supported in the service, though that also isn’t working everywhere yet.

Under the FCC’s new rules, all covered text providers must support text-to-911 by Dec. 31, 2014, but for now you can check this list [PDF] to see if your area made the cut.

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