A:Answer If you cast an item from Netflix to your Vizio television, so long as you have a 4K netflix subscription,and your internet speed is fast enough, the cast will be in 4k. It does not matter what your phone can do or not. Your phone does not stream the data to the TV in any way (unless you are casting a video to the tv that's actually stored on your phone). The way Cast works is that your phone basically tells the Television what it should start streaming. The tv is doing the streaming/downloading from Netflix, not the phone.