I mean, they do demonstrably work. And if for some reason yours doesn't, no big deal, just walk two feet over to the gate desk and ask them to print you one.

I mean, they do demonstrably work. And if for some reason yours doesn't, no big deal, just walk two feet over to the gate desk and ask them to print you one. I prefer to use mobile boarding passes so I don't have to waste paper, and don't have to keep track of yet one more thing while traveling. (I'm already bringing my phone, so I have to keep track of that regardless.)