watchOS 5.3 (build 16U5526f) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2019-05-15T17:11:37Z. The update package is 92.11 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: 0aa288cb465b7eb7ab87cfc2876498fd6519c892.zip.