watchOS 5.3.8 (build 16U680) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2020-07-15T17:28:32Z. The update package is 54.73 MB. This is a delta (partial) update that requires 5.3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: e0e67560bbab46cd8311530d29898fe37d8491ff.zip.