watchOS 5.3 (build 16U5558b) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2019-06-24T17:25:09Z. The update package is 142.91 MB. This is a delta (partial) update that requires 5.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: b2766e610bf7aa77d224c3b23e09e670a89bc602.zip.