watchOS 5.3 (build 16U5545c) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2019-06-11T17:13:45Z. The update package is 165.24 MB. This is a delta (partial) update that requires 5.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 5b10d6595599dc063b11e84eee8d13ce84f92eec.zip.