watchOS 5.1 (build 16R5577c) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-10-09T17:12:12Z. The update package is 752.58 MB. This is a delta (partial) update that requires 4.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 1ed84b5f886138a28ef9a95e118e8acd655a6e34.zip.