YouTube announced a “Signature Device” program that’s meant to signify which smartphones offer the “best experience” when streaming videos from the platform. Right now, it’s all Android smartphones and no iOS devices. This is due to Apple’s lack of support for the VP9 codec. iPhones check off all other requirements to earn the Signature Device badge except for hardware decoding of VP9.
The codec requires less bandwidth for high-resolution videos, but Apple has yet to embrace it across iOS, macOS, or the Apple TV. As a result, most of Apple’s devices — including the Apple TV 4K — remain capped at 1080p resolution. (Higher-res video can be viewed in Chrome on Macs.)