tvOS 11.3 (build 15L5164e) is an official Apple over-the-air update for the Apple TV 4 (2015), released on 2018-01-25T23:02:49Z. The update package is 298.92 MB. This is a delta (partial) update that requires 11.2.5 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 7364a29e967b666605591358b0822fd44bb30568.zip.