watchOS 5.3.10 (build 16U711) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2026-03-24T18:33:57Z. The update package is 63 MB. This is a delta (partial) update that requires 5.3.1 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: cb17a9bacab2787e5c6cb678476817d347a71fdf.zip.