Apple announced two new Apple Watch models at its September 9 event — the Apple Watch Series 12 and the Apple Watch Ultra 4. Both get Apple's new S12 chip, making them fully Siri AI compatible, and both feature a completely redesigned Health Sensing System that Apple says delivers the most accurate heart rate measurement in a consumer wearable.
Apple Watch Series 12
The Series 12 looks similar to the Series 11 in design, but the upgrades under the hood are meaningful. The new S12 chip enables full Siri AI support — including hands-free AI conversation via compatible AirPods, and on-device processing for health data. The Health Sensing System has been completely rebuilt: the electrode surface area has been increased, photodiodes redesigned, and LEDs made larger and more power-efficient.
Battery life gets a notable boost over the Series 11, and Apple is introducing a ceramic case option — a premium material previously only available on older Apple Watch Edition models. The new Readiness app launches as a default home screen app, offering an improved recovery tracking experience. The Workout app gets a redesign that lets you track individual reps and sets for strength training.
| Specification | Apple Watch Series 12 |
|---|---|
| Chip | S12 |
| Health Sensing | Redesigned electrode, photodiodes and LEDs |
| Siri AI | Full support |
| New Features | Readiness app, Workout redesign, rep/set tracking |
| Case Options | Aluminium, Stainless Steel, Ceramic (new) |
| watchOS | watchOS 27 |
Apple Watch Ultra 4
The Ultra 4 is the more significant update of the two. It gets a new chipset, new sensors, and two standout software features:
Live Rewind — missed something someone said? Live Rewind lets you see a real-time transcription of the last few seconds of audio, so you can read back what you missed. Powered entirely on-device.
Siri Recap — at the end of your day, Siri Recap summarises what happened based on your activities, health data, and notifications. All processing happens on-device and nothing is sent to Apple's servers.
The Ultra 4 also gets always-on heart rate data tracking — monitoring your activity and recovery continuously over 24 hours. This sensor capability is exclusive to the Ultra 4 and not available on the Series 12.
| Specification | Apple Watch Ultra 4 |
|---|---|
| Chip | New Apple silicon (Ultra-class) |
| Always-On Heart Rate | 24-hour continuous monitoring |
| Live Rewind | Real-time audio transcription on wrist |
| Siri Recap | Daily summary from activity and health data |
| Case | Titanium |
| watchOS | watchOS 27 |
Our Take
The Series 12 is a solid update — particularly the Siri AI integration and the new health sensors — but it's not a dramatic visual departure from the Series 11. If you're on a Series 9 or older, it's a worthwhile upgrade. Series 10 or 11 owners can probably wait.
The Ultra 4 is more compelling for serious athletes and health trackers. Live Rewind and Siri Recap are genuinely useful daily features, and the always-on heart rate monitoring is unique to this model.
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