watchOS 4.3 (build 15T5212a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-03-16T20:09:46Z. The update package is 331.37 MB. This is a delta (partial) update that requires 4.2.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: de3c85e23304218759aad98f886a8a70a8ec6095.zip.