watchOS 5.3 (build 16U5526f) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm, LTE), released on 2019-05-15T17:12:57Z. The update package is 474.49 MB. This is a delta (partial) update that requires 5.1.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 0a15248a02734158f5b201902c8a7a3149045e9e.zip.