watchOS 4.1 (build 15R5835d) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2017-10-09T17:05:13Z. The update package is 138.11 MB. This is a delta (partial) update that requires 4.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: bb4a24888d2512fcd52a9ba41f0f3ae79d3436fe.zip.