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You can’t remotely wipe or reset Apple TV like you can iPhone, iPad or a Mac. However, you can remove the device from your Apple ID account. The new owner will most likely reset the device in order to login with their own Apple ID, otherwise they will be nagged to enter your Apple ID password all the time. I wouldn’t worry about your purchased content.

 
You can’t remotely wipe or reset Apple TV like you can iPhone, iPad or a Mac. However, you can remove the device from your Apple ID account. The new owner will most likely reset the device in order to login with their own Apple ID, otherwise they will be nagged to enter your Apple ID password all the time. I wouldn’t worry about your purchased content.

Cool so I assume they can’t see purchased content after you remove Apple device from list?
 
So I tried this at a friends house. Removed device changed password. Asks for password promt but still plays music and videos any tips how I can stop them being used?
 
you could also try changing your appleID password, it looks like you're given the option to log out all devices


If, like me, you have multiple devices associated with your Apple ID, you’ll see a message asking if you wish to sign out of all devices. Choose Sign Out of Other Devices, as those devices will stop working soon after the new password takes effect
 
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