tvOS 12.0 (build 16J5355a) is an official Apple over-the-air update for the Apple TV 4K, released on 2018-08-20T17:16:52Z. The update package is 1.59 GB. This is a full OTA update that can be applied from any compatible base version. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 17798fecadfb54bb0d65def6ea5f2310d404992a.zip.