watchOS 4.1 (build 15R5835d) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2017-10-09T17:05:06Z. The update package is 136.42 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: 20ed19cf4250f703f3e42a9afb36c011dd77887c.zip.