watchOS 5.3 (build 16U5537b) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2019-05-28T17:12:27Z. The update package is 222.4 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: dfe6e4c620a1472e2e36157a4b8aea1c165f07a5.zip.