Dubbed the YouTube Device Report, YouTube says, “With a Signature Device, you can enjoy vivid HDR videos, immersive 360° video, and fast video load times – all while using less bandwidth. To qualify as a Signature Device, a phone must support high dynamic range, high frame rate, reliable DRM performance, 4K decoding, and use next generation video codecs.”
This means that not every handset out there can be considered to be a Signature Device, even if it is the company’s flagship model. As you can tell from the list, it seems that Apple’s iPhone is missing from it. This is because Apple does not support the VP9 video codec which is what Google developed and uses, and is also why Safari doesn’t have the ability to stream YouTube in 4K.
Of course this doesn’t mean that the iPhone is a bad device to watch YouTube on, it just makes for better marketing to be able to call your device a “YouTube Signature Device”. Many iPhone users have no issues watching YouTube on their phones and we doubt that this will change.