watchOS 5.1 (build 16R5577c) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2018-10-09T17:12:06Z. The update package is 169.54 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: a6a937a90b9412fbb21bcf83c9eb80fb52c8e4b1.zip.