watchOS 5.3 (build 16U5526f) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2019-05-15T17:11:35Z. The update package is 212.99 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: 4cf694621a648c483ec24ee5c3654a2e0a483d72.zip.