watchOS 5.1 (build 16R5589c) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2018-10-22T17:19:03Z. The update package is 118.79 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: 825ef78f42a630eaa4adccfe96a983e3cf128f7f.zip.