watchOS 5.3 (build 16U5569a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2019-07-16T17:14:29Z. The update package is 135.79 MB. This is a delta (partial) update that requires 5.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: c0f78b56e1418c0e002c522a30eb5c5d11e68c66.zip.