Apple has officially introduced the Apple Watch Series 12, bringing a new Health Sensing System that significantly increases how frequently the smartwatch collects heart and heart rate variability data. The new model also introduces a daily readiness score, longer workout battery life, faster charging, improved step tracking, and a new collection of Apple Intelligence features.

The Apple Watch Series 12 is built around Apple’s new S11 chip and a redesigned sensor system that the company says delivers its most accurate heart rate sensing yet in a wearable. Apple says a study involving more than 1,000 participants found that the new Apple Watch had the highest heart rate accuracy among the leading wearables tested.

The Series 12 is available in 42mm and 46mm sizes, with aluminum, titanium, and a new ceramic option. Preorders start today, September 9, with the watch arriving in stores on September 18. Pricing starts at $399 in the U.S.

The Health Sensing System is the big story

The centerpiece of the Apple Watch Series 12 is its new Health Sensing System, which combines new optical and electrical heart sensors with the S11 chip.

One of the more interesting changes is how often the watch measures heart rate. Apple says Series 12 can now measure heart rate every five seconds throughout the day, using larger and more power-efficient green LEDs in its optical heart sensor.

That more frequent data collection is intended to give the watch a better picture of a user’s physiological state while also improving the accuracy of features such as the Exercise and Move rings. Users can also see their real-time heart rate through an updated Heart Rate app and a new watch face complication.

Apple is also dramatically increasing the frequency of heart rate variability, or HRV, measurements. HRV can provide useful information about stress and recovery, and Apple Watch Series 12 can measure it up to 24 times more frequently than before.

The watch separates HRV into two measurements: Recovery HRV, which is aimed at understanding daily signals related to stress and recovery, and overall HRV, which provides broader information, including cardiovascular-related insights.

The Vitals app is getting an upgrade as well. Overnight vitals can now include Recovery HRV compared against a user’s personal baseline, while a new daytime view allows users to look at their metrics during the day and potentially notice changes before they appear in overnight measurements.

Readiness gives the Apple Watch a new daily score

Apple is also adding a feature that will look familiar to anyone who has used fitness trackers focused on recovery: Readiness.

Apple Watch Series 12 analyzes recent activity, training load, vitals, and sleep score to produce a single score from 0 to 10. Instead of leaving users to interpret the number themselves, Apple pairs it with one of four recommendations: Recover, Pace Yourself, Ready, or Go For It.

The score isn’t necessarily fixed for the entire day. Apple says Readiness can update as new information arrives, such as after an intense workout or when daytime vitals change.

The algorithm was developed using data from Apple’s Heart and Movement Study, working with exercise scientists and physicians at Apple.

It’s a notable shift for Apple Watch. Rather than simply showing users a growing collection of health metrics, Apple is increasingly trying to turn those measurements into something actionable.

More battery life during workouts

Battery life isn’t getting a dramatic overhaul, but Apple is squeezing more endurance out of the Series 12 where it matters.

The watch continues to offer up to 24 hours of everyday battery life, but outdoor workout battery life has increased to as much as 10 hours, which Apple says is 25 percent longer than the previous model.

Charging is faster too. Apple says 15 minutes of charging can provide up to 12 hours of additional battery life, a 50 percent improvement over the previous generation.

That should make the Series 12 a little easier to live with for people who use the watch for both daytime activity tracking and overnight sleep monitoring.

Apple says step tracking is more accurate

The Series 12 also gets a completely redesigned pedometer model.

Apple is using new machine learning algorithms to improve distance measurements during indoor walking and running workouts, while the S11 chip contributes to more accurate step counting throughout the day.

The company goes as far as calling the Series 12 the most accurate step-tracking smartwatch, and there’s now a dedicated Steps complication for putting the count directly on the watch face.

Apple Watch Series 12 gets Apple Intelligence features

Health isn’t the only area getting attention. The S11 chip also enables a new group of Audio Intelligence features that Apple says will arrive later this year.

One of the most interesting is Sound Recognition, which brings the feature directly to Apple Watch. It can recognize sounds such as sirens, alarms, doorbells, and a crying baby and alert users when they’re detected, even when their iPhone isn’t nearby.

Then there’s Live Rewind, which can show the previous 15 seconds of a conversation as text after a double press of the Digital Crown. It’s designed for those moments when you realize you missed something someone just said.

Siri Recap goes a step further by generating a high-level summary of a conversation, including a title and key points that can be reviewed later.

The watch also gets Shazam integration that can identify music playing nearby and display the song and artist in the Smart Stack.

Apple is emphasizing privacy with these features. The company says the Audio Intelligence system doesn’t create or store audio recordings, while raw audio used during processing is inaccessible to the operating system, apps, the user, and Apple. The S11 chip includes a Secure Exclave that processes the audio in an isolated hardware environment before immediately deleting it.

Live Rewind and Siri Recap will arrive in beta later this year.

Siri is getting smarter on the wrist

With watchOS 27, Apple Watch Series 12 also supports a new version of Siri powered by Apple Intelligence.

Apple says the new Siri can understand personal context and provide access to broader world knowledge, while a new Siri app allows users to continue conversations from their wrist. There’s also a new Siri Modular watch face designed to make the assistant easier to access.

watchOS 27 adds several other changes, including a dynamic app grid with Siri-suggested apps, new single-handed tap interactions, more context-aware Smart Stack suggestions, and support for perimenopause and menopause tracking.

Workout Buddy can now also work directly on Apple Watch when the iPhone isn’t nearby, while Spanish support joins English.

The Health app is getting a major redesign

Some of the most ambitious health changes won’t actually arrive on the watch itself.

Apple is redesigning the Health app on iPhone with Apple Intelligence, adding new Insights and Longevity sections. The Insights tab will surface timely information across areas such as heart health, sleep, readiness, fitness, vitals, and cycle tracking.

The Longevity tab takes a longer-term view of a user’s health data. One of its headline features is Health Age, which uses Apple Watch data to show how certain health metrics are tracking relative to a user’s chronological age.

Apple says the system can consider measurements including VO2 max, resting heart rate, sleep, and HRV, with users also able to add certain lab information such as A1c and LDL.

The redesigned Health app will also offer movement evaluations using the iPhone’s camera and Apple Watch heart rate data. These assessments can measure areas including flexibility, strength, balance, movement mechanics, and VO2 max.

For U.S. users, Apple says the Health app will eventually allow them to schedule and purchase lab testing covering more than 50 biomarkers for $119 through approximately 2,000 Quest Diagnostics locations.

The redesigned Health app is expected later this year, initially in U.S. English.

New finishes, ceramic design, and tougher glass

The Series 12 comes in 42mm and 46mm sizes.

Aluminum models are available in dark bronze, black, light gold, and space gray, while titanium models come in radiant gold and natural titanium. Apple is also introducing a ceramic version in pearl white and night blue.

Aluminum models use Ceramic Shield 2, which Apple says is 60 percent tougher than the Ion-X glass used on previous aluminum models.

The watch is also available with a new selection of Sport Bands, Sport Loops, Modern Buckle bands, and Milanese Loop finishes, including new colors and plaid Sport Loop designs.

Apple Watch Series 12 price and availability

Apple Watch Series 12 starts at $399 in the U.S. Preorders are available now, with the first units and in-store availability arriving September 18.

watchOS 27 arrives September 14 for Apple Watch Series 9 and later, Apple Watch SE 3, and Apple Watch Ultra 2 and later. The update requires an iPhone 11 or later or iPhone SE (2nd generation or later) running iOS 27 or later.

The Apple Watch Series 12 is therefore less about introducing one flashy new health sensor and more about turning the watch into a much more frequent health-monitoring device. Heart rate every five seconds, dramatically more frequent HRV measurements, daytime vitals, and Readiness give Apple considerably more data to work with.

And with the redesigned Health app and Apple Intelligence waiting on the other side, Apple is clearly trying to make all that data more understandable rather than simply giving users another pile of numbers to stare at.