watchOS 5.3 (build 16U5566a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2019-07-09T17:19:57Z. The update package is 79.66 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: 57fc6423c7a84646ebb29b6e2a3c55c9a7cc28ec.zip.