Apple unveils Watch Series 12 and Ultra 4 with upgraded health sensors and S11 chip

Redesigned health sensors and Readiness score

Apple introduced the Apple Watch Series 12 and Apple Watch Ultra 4 at its September 9, 2026 product event. Both smartwatches feature a re-engineered Health Sensing System on the rear casing, combining enlarged EKG electrodes, reconfigured photodiodes, and an efficient green LED layout that resembles a sundial. The updated hardware increases biometric sampling rates, taking heart rate readings every five seconds compared to every five minutes on previous generations, while heart rate variability measurements occur every five minutes instead of every two hours. These continuous inputs feed Apple's new Readiness app, which scores recovery on a 1 to 10 scale using seven consecutive nights of sleep baseline data, vitals such as skin temperature and blood oxygen, and training load from native or third-party fitness apps.

Craig Bolton, Director of Fitness Technologies at Apple, noted why the capability arrived with this hardware release:

It's down to the evolution and the advancements we've made in the hardware technology, which has really brought about this to be the right time.

Battery endurance and charging upgrades

Hardware optimizations and adjusted battery capacities yield different runtimes across the two models. The Series 12 delivers 24 hours of normal use on a single charge, representing a six-hour gain over the 18-hour specification of the Series 8 through Series 11 models. The Ultra 4 incorporates a 5% larger battery cell, enabling 50 hours of standard runtime with the always-on display active, 84 hours in Low Power Mode, and 45 hours in Max Extended Workout Mode. Ultra 4 packages also include an updated fast-charging cable engineered to deliver up to 18 hours of battery life from a 15-minute charge.

Processing power and Audio Intelligence

Both watch lines run on the new S11 system-on-chip, an architecture derived from the A20 Pro with a dedicated Neural Engine, GPU, and an isolated Secure Enclave for microphone processing. The silicon underpins watchOS 27, placing Siri and machine learning utilities at the center of the software interface. The platform introduces Audio Intelligence features, such as accelerated Shazam recognition and ambient Sound Recognition for users with hearing difficulties. Later in 2026, Apple plans to deploy ambient recording tools, named Siri Recap and Live Rewind, alongside longevity metrics including Health Age.

Case materials, display glass, and finish options

The Series 12 arrives in 44mm and 46mm sizes with curved Always-On OLED displays and backward compatibility for existing watch bands. The chassis measures 9.7 millimeters thick in aluminum and titanium, standing as the thinnest Apple Watch profile to date, while the ceramic model measures 9.85 millimeters. Ceramic cases return in pearl white and night blue after being discontinued in 2020. Aluminum models feature Ceramic Shield 2 glass and offer dark bronze, black, space gray, and light gold finishes, while titanium models add radiant gold alongside natural titanium. The Ultra 4 maintains its rugged enclosure, existing color palette, and price point, retaining dual-band GPS, hypertension notifications, and off-grid satellite connectivity.