How do you snap a app in the new update..?

Snap is no longer a feature on the console. If you are looking to use Twitch then you can open the app while a game is running and select Broadcast. After that you would need to have a pc or laptop nearby to see any comments on the stream.

You now have the ability with the June update to change the volume on snapped apps. All you have to do is go to your settings and select sound mixer and it allows you to change the volume one snapped apps. Hope this helped.

You need to have the Xbox Music App installed, but yes, music works the same way. I haven't figured out how to get it to play over the background without snapping the music app, but I'm sure an update will clear that up because it seems like a nice feature
to have.

Perhaps a command to 'hide' the snapped app and another command to 'show' the snapped app so that you don't need to exit out of the app when you want to get it out of the way.

I have NFL app snapped, watching games. None of the scores/times update on the snap/app. Still showing Q1 15:00 in all games, when most are well into the game. This a bug? How to fix??

Yeah, Skype doesn't support being snapped to the right side of the screen just yet - FAQ on the app information page says it's being worked on for release in a future update. For those apps that do fully support the Snap feature - if you wanted to switch
between the two, all you'd have to do is either say "Xbox, switch" or double tap the Xbox button on your controller.

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If you want to know what applications can be snapped, go to "My Games & Apps", select the Snap app, and it should display any items that you're able to snap.