My phone displays on my tv while using Airplay, but when I try to watch a video full screen on say YouTube it won’t display on the tv, why is that?

Hello YonkoChris,

This page can help out with using AirPlay to stream video: Use AirPlay to stream video or mirror the screen of your iPhone, iPad, or iPod touch

Stream video from your iPhone, iPad, or iPod touch to a TV

1. Connect your device to the same Wi-Fi network as your Apple TV or AirPlay 2-compatible smart TV.

2. Find the video that you want to stream.

3. Tap AirPlay . In some apps, you might need to tap a different button first.1 For example, in the Photos app, tap Share , then tap AirPlay .

4. Choose your Apple TV or AirPlay 2-compatible smart TV.

To stop streaming, tap AirPlay  in the app that you're streaming from, then tap your iPhone, iPad, or iPod touch from the list.

Steps here can help out with issues that may come up:

1. Make sure that your AirPlay-compatible devices are turned on and near each other.

2. Check that the devices are updated to the latest software and are on the same Wi-Fi network. 

3. Restart the devices that you want to use with AirPlay or screen mirroring.

If you're prompted to enter a password, you might have restrictions turned on, or you might need to adjust your AirPlay password settings.

Cheers.