Stream video content consumes data, that is a fact. However, it seems that if you’re an AT&T subscriber and you’re also subscribed to HBO Max (which launched late April), it looks like streaming HBO Max on your mobile device won’t actually count towards your data cap, meaning that you’ll essentially be able to stream it unlimited without worrying about it consuming your mobile data allocation.
This was initially brought up during the Vergecast in which they spoke with Tony Goncalves, the AT&T executive in charge of HBO Max. They asked Goncalves if HBO max would count towards the user’s data cap, in which Goncalves claimed not to have the answer, but AT&T later followed up with a confirmation that it would not.
Apparently, this is due to a sponsored data system which allows companies to pay carriers such as AT&T to exclude themselves from data caps. In a way, it would be like the streaming company is paying for the user’s data. However, it should be noted that since AT&T owns HBO, they are basically paying themselves.
The bad news is that this is only for HBO Max, so if you’re using a different streaming service like Netflix or Disney+, then it will count towards your data cap, so you might want to keep an eye out for that.