watchOS 5.3 (build 16U569) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2019-07-22T19:15:02Z. The update package is 499.4 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: e43856034212634ab918b0b0087860b071821a72.zip.