If you’ve got an older iOS device running something older than iOS7 then you’ll find the YouTube app will no longer work. This is because the YouTube Data API has been updated to support newer features, according to an official Google document.
Devices capped at iOS 6 or earlier won’t be without access to YouTube – m.youtube.com through Safari or another browser will still work. But if you have an first or second generation model Apple TV then access YouTube will no longer work with no workarounds other than potentially jailbreaking the device and finding a solution that way.
Older non-Apple platforms, such as Google TV devices still running version 2, some game consoles, and a collection of Sony and Panasonic TVs and Blu-ray players are also affected. A general rule is products made 2012 or earlier are going to lose their YouTube access.
Users of some of the affected devices will see a multi-language YouTube video informing them of the shutdown.
You can see a list of all the affected services on the YouTube help channel.