watchOS 5.3 (build 16U5537b) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2019-05-28T17:13:04Z. The update package is 114.69 MB. This is a delta (partial) update that requires 5.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 9b67af06d5c3902fb554e64ced06c9ebd259f6b7.zip.