watchOS 5.1 (build 16R5568d) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2018-10-02T17:14:57Z. The update package is 140.48 MB. This is a delta (partial) update that requires 5.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: ddd38d503c7c5b29b365e6eb13e775b13465d161.zip.