tvOS 13.3.1 (build 17K795) is an official Apple over-the-air update for the Apple TV 4 (2015), released on 2020-01-28T18:42:23Z. The update package is 1.42 GB. This is a delta (partial) update that requires 9.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: a10a19d84cadd0b68bcf8d04226253f93b72b248.zip.