watchOS 3 is the third release of watchOS, shipped September 13, 2016 — the platform's great rescue. Apple kept favorite apps resident in memory with background refresh, making launches effectively instant on the same hardware that had crawled for two years; the side button repurposed from friend-dialing to an app Dock; and Control Center swiped up from the bottom, aligning the watch with iOS conventions.

Instant-launch Dock and background refresh; Control Center; Scribble handwriting; SOS emergency calling; the Breathe app; activity sharing and wheelchair workouts; and Minnie Mouse/activity-focused faces.

watchOS 3 is the platform's iOS 12 — the performance release that made the product feel finished — and its resident-app model, Dock, and Control Center became watchOS's permanent furniture. Reviewers dated the Apple Watch's product-market fit from this release and the Series 2 fitness pivot it accompanied.