watchOS 5.3 (build 16U5566a) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2019-07-09T17:20:14Z. The update package is 144.31 MB. This is a delta (partial) update that requires 5.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 87d93375622f38e4f627c4e5515b6343067a0529.zip.