watchOS 5.3 (build 16U6569) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2019-07-22T19:17:23Z. The update package is 147.47 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: 9fbfc859dc9ab3aa458ccc9d928dea6b30af5de3.zip.