is needed. 50 and 66 GB use two layers, and 100 GB uses three layers.

Unlike conventional DVDs and Blu-rays, the 4K format does not officially have region coding, although some releases have been reported to conditionally prevent playback based on player region. Ultra HD Blu-ray uses a new revision of AACS DRM: AACS 2. AACS 2.1 is used on certain releases such as Stand by Me,