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Apple Watch Series 12 and Apple Watch Ultra 4 keep the familiar look of their predecessors, but their main changes are inside: a redesigned health-sensing system, more frequent heart-rate and HRV readings, updated Vitals and Readiness features, and Apple’s S11 chip. Series 12 offers more case materials and finishes; Ultra 4 is the better fit for people who need longer battery life. The strongest upgrade case is for owners of Series 9 or Ultra 2, while owners of newer models should weigh how much they value the health updates.
That is the conclusion of Chance Miller’s hands-on review, published September 17, 2026, after a week with the watches. Its observations are useful for understanding the changes, but one week is not enough to establish the long-term value of Readiness or other new health features. Read the 9to5Mac review.
What changes in Series 12 and Ultra 4?
The review describes both watches as visually similar to their predecessors, with the substantial changes under the case. Both use Apple’s S11 chip, which Apple calls its most powerful wearable chip. Miller noticed faster app launches and interactions in a brief comparison with Ultra 3; this is a reviewer observation, not a benchmark. Apple also says the chip supports health sensing, Audio Intelligence and a redesigned pedometer model.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchThe review reports that Series 12’s display area is about 2% smaller than Series 10 and Series 11 despite retaining the overall pixel count, and that its case is about 1 mm wider. Miller did not notice those differences in ordinary use. These dimensions and configurations are details reported in the review, rather than independently confirmed specifications here.
#1 Best Overall
![Apple Watch Series 11 [GPS 46mm] Smartwatch with Jet Black Aluminum Case with Black Sport Band - M/L. Sleep Score, Fitness Tracker, Health Monitoring, Always-On Display, Water Resistant](https://m.media-amazon.com/images/I/416RQ0rtsUL._SL160_.jpg)
- A FULL-FEATURED HEALTH TRACKER—Apple Watch Series 11 gives you invaluable insights about your body, right from your wrist. Take an ECG anytime* and get alerts for a high and low heart rate or an irregular rhythm*—so you can stay closer to your heart. You can also view your overnight health tracking metrics with the Vitals app* and be notified of possible sleep apnea.*
- KNOW YOUR SLEEP SCORE—With advanced sleep tracking, Series 11 gives you a daily sleep score. It’s an easy way to help measure and understand the quality of your sleep, so you can make it more restorative.
- GET HYPERTENSION NOTIFICATIONS—Did you know that Series 11 can spot signs of chronic high blood pressure? By analyzing how your blood vessels respond to beats of the heart, it can notify you of possible hypertension.*
- SAFETY FEATURES—A smartwatch that puts your safety first. Series 11 can detect a hard fall or severe car crash, automatically help connect you with emergency services, and notify your emergency contacts.* Check In can automatically notify a loved one when you’ve arrived at your destination.
- A POWERFUL FITNESS TRACKER—With advanced metrics and motivating features like Pacer, Heart Rate Zones, training load, and Workout Buddy powered by Apple Intelligence from your nearby iPhone*—Series 11 is made to help everyone stay active, from runners and hikers to strength-training enthusiasts.
How do the watches differ in materials and finishes?
| Model | Construction and finishes described in the review | Best fit |
|---|---|---|
| Apple Watch Series 12 | Aluminum in Dark Bronze, Light Gold, Black and Space Gray; titanium in Radiant Gold and Natural; ceramic in Night Blue and Pearl White. | People who want a broader selection of materials and finishes. |
| Apple Watch Ultra 4 | Titanium in Natural and Black. | People who prioritize the Ultra line’s longer battery estimates and outdoor-workout options. |
The review also describes a redesigned translucent silicone Ultra Ocean Band in translucent gray, translucent kelp and translucent black, which Miller found lighter-feeling. Band and case compatibility varies by connector, so check the specific watch and band before buying.
What do the new health features actually do?
Heart-rate sensing
The review attributes three sensor changes to Apple: greater ECG electrode contact area, photodiodes arranged in a ring, and larger green LEDs. It reports that the watches can record heart rate every five seconds whether the wearer is moving or still. That is a change from an earlier approach that, according to the review, attempted a reading every five minutes while the user was mostly stationary.
Apple claims the system delivered statistically better overall accuracy than competing wearables in a study of more than 1,000 participants. The review does not provide the underlying study, its methods or its results table, so this remains a manufacturer claim rather than an independently assessable comparison. Apple also calls it “the most accurate heart rate sensing in a wearable”; that phrase should likewise be understood as Apple’s claim.
Rank #2
![Apple Watch Series 11 [GPS 42mm] Smartwatch with Rose Gold Aluminum Case with Light Blush Sport Band - S/M. Sleep Score, Fitness Tracker, Health Monitoring, Always-On Display, Water Resistant](https://m.media-amazon.com/images/I/31caPPnRysL._SL160_.jpg)
- A FULL-FEATURED HEALTH TRACKER—Apple Watch Series 11 gives you invaluable insights about your body, right from your wrist. Take an ECG anytime* and get alerts for a high and low heart rate or an irregular rhythm*—so you can stay closer to your heart. You can also view your overnight health tracking metrics with the Vitals app* and be notified of possible sleep apnea.*
- KNOW YOUR SLEEP SCORE—With advanced sleep tracking, Series 11 gives you a daily sleep score. It’s an easy way to help measure and understand the quality of your sleep, so you can make it more restorative.
- GET HYPERTENSION NOTIFICATIONS—Did you know that Series 11 can spot signs of chronic high blood pressure? By analyzing how your blood vessels respond to beats of the heart, it can notify you of possible hypertension.*
- SAFETY FEATURES—A smartwatch that puts your safety first. Series 11 can detect a hard fall or severe car crash, automatically help connect you with emergency services, and notify your emergency contacts.* Check In can automatically notify a loved one when you’ve arrived at your destination.
- A POWERFUL FITNESS TRACKER—With advanced metrics and motivating features like Pacer, Heart Rate Zones, training load, and Workout Buddy powered by Apple Intelligence from your nearby iPhone*—Series 11 is made to help everyone stay active, from runners and hikers to strength-training enthusiasts.
Miller found the more frequent readings useful for observing everyday activity. The review says the Heart Rate app now displays a graph of the last two minutes and offers two heart-rate complications. In his initial use, he did not notice a clear change in personal calorie estimates or improved automatic workout detection. Those are individual observations from a short review period, not general performance findings.
HRV and Vitals
The review says heart-rate variability (HRV) may be sampled as often as every five minutes while at rest, compared with once every two hours previously, and describes a new recovery HRV measurement. It also describes a daytime Vitals view with four categories—“notably off,” “slightly off,” “typical” and “favorable”—instead of a two-category approach.
Readiness
Readiness combines recent activity, training load, vitals and sleep score. It requires a week of sleep data and can update during the day based on naps, activity and daytime heart rate. The review describes Apple’s score bands as 0–1 for Recover, 2–4 for Pace Yourself, 5–7 for Ready and 8–10 for Go For It.
Rank #3
![Apple Watch Series 11 [GPS 42mm] Smartwatch with Jet Black Aluminum Case with Black Sport Band - S/M. Sleep Score, Fitness Tracker, Health Monitoring, Always-On Display, Water Resistant](https://m.media-amazon.com/images/I/41s72HIk5TL._SL160_.jpg)
- A FULL-FEATURED HEALTH TRACKER—Apple Watch Series 11 gives you invaluable insights about your body, right from your wrist. Take an ECG anytime* and get alerts for a high and low heart rate or an irregular rhythm*—so you can stay closer to your heart. You can also view your overnight health tracking metrics with the Vitals app* and be notified of possible sleep apnea.*
- KNOW YOUR SLEEP SCORE—With advanced sleep tracking, Series 11 gives you a daily sleep score. It’s an easy way to help measure and understand the quality of your sleep, so you can make it more restorative.
- GET HYPERTENSION NOTIFICATIONS—Did you know that Series 11 can spot signs of chronic high blood pressure? By analyzing how your blood vessels respond to beats of the heart, it can notify you of possible hypertension.*
- SAFETY FEATURES—A smartwatch that puts your safety first. Series 11 can detect a hard fall or severe car crash, automatically help connect you with emergency services, and notify your emergency contacts.* Check In can automatically notify a loved one when you’ve arrived at your destination.
- A POWERFUL FITNESS TRACKER—With advanced metrics and motivating features like Pacer, Heart Rate Zones, training load, and Workout Buddy powered by Apple Intelligence from your nearby iPhone*—Series 11 is made to help everyone stay active, from runners and hikers to strength-training enthusiasts.
Miller had only one score after a week of use, so the review does not establish whether Readiness offers dependable long-term guidance. Treat it as a new feature to evaluate against your own experience, rather than as a proven reason by itself to upgrade.
Which model makes more sense for your battery needs?
The figures below are battery estimates and workout durations reported in the September 17 review; they are not directly comparable to the reviewer’s individual use period.
| Model | Apple-reported normal use | Apple-reported Low Power Mode | Workout figures reported in the review |
|---|---|---|---|
| Series 12 | 24 hours, matching the Series 11 claim according to the review | 38 hours, matching the Series 11 claim according to the review | 10 hours of outdoor workout time |
| Ultra 4 | 50 hours; the review compares this with 42 hours for Ultra 3 | 84 hours; the review compares this with 72 hours for Ultra 3 | 18 hours of standard workouts, 25 hours of Extended workouts and 45 hours of Max Extended workouts |
For one Ultra 4 use period, Miller reported charging at about 8 p.m. Sunday and again at about 8 p.m. Tuesday—roughly 48 hours apart. That period included 90 minutes of workout tracking, three hours away from iPhone and two nights of sleep tracking. It was an individual account, not a controlled battery test.
Rank #4
![Apple Watch Ultra 3 [GPS + Cellular 49mm] Running & Multisport Smartwatch w/Rugged Titanium Case w/Blue/Bright Blue Trail Loop - M/L. Satellite Communications, Advanced Health & Fitness Tracking](https://m.media-amazon.com/images/I/51SKumOyv8L._SL160_.jpg)
- RUGGED AND READY TO GO—The ultimate sports and adventure smartwatch is built to last with an extremely tough titanium case and a strong sapphire crystal display. Water resistant up to 100m—it’s great for swimmers, divers, and fans of high-speed water sports.*
- A FULL-FEATURED HEALTH TRACKER—Ultra 3 can take an ECG* and check your heart rhythm for signs of AFib—right from your wrist. The smartwatch sends alerts for possible hypertension,* an irregular heart rhythm,* or an unusually high or low heart rate. You can view your overnight health tracking metrics with the Vitals app,* track your sleep score, and take readings of your blood oxygen.*
- ULTIMATE RUNNING AND WORKOUT COMPANION—A superior fitness tracker for marathoners, triathletes, mountain bikers, backcountry hikers, and mountain climbers, Ultra 3 provides precision dual-frequency GPS, Pacer, Heart Rate Zones, Custom Workouts, running power, Workout Buddy powered by Apple Intelligence from your nearby iPhone,* training load, and more.
- KEEP HELP CLOSE AT HAND—Ultra 3 is a smartwatch that can detect a hard fall or severe car crash* and automatically help connect you to emergency services and notify your emergency contacts. Check In can automatically notify a loved one when you’ve arrived at your destination.
- MULTIDAY BATTERY LIFE—Ultra 3 is a smartwatch that’s engineered to give you even longer battery life. It’s perfect for trail runners—with up to 42 hours of normal use and up to 72 hours in Low Power Mode.* Track a workout with full GPS and heart rate monitoring for up to 20 hours in Low Power Mode.*
Should you upgrade from your current Apple Watch?
Consider upgrading from Series 9 or Ultra 2
The reviewer specifically identifies Series 9 and Ultra 2 owners as people with more reason to consider an upgrade. The case is strongest if you want the new sensing and health features, and, for Ultra 2 owners, the battery-related changes described for Ultra 4. The review does not establish current prices or the cost of upgrading, so compare the purchase cost in your region before deciding.
Think carefully if you have a newer model
If your current watch is newer, the watches’ familiar design and the reviewer’s focus on internal changes make the decision more dependent on your interest in health data. More frequent heart-rate and HRV readings, updated Vitals and Readiness may matter to you; if they do not, the review offers less reason to replace a recent watch.
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- Choose Series 12 if you want a choice of aluminum, titanium or ceramic configurations and Apple’s reported 24-hour normal-use estimate suits your routine.
- Choose Ultra 4 if its reported longer battery estimates and workout-duration options better match your use, and you prefer its titanium construction.
- Base either choice on the health features only if you expect to use the extra readings and metrics; the review’s short trial does not settle their long-term usefulness.
Which software features were still pending in the review?
As of the review’s September 17, 2026 publication, a redesigned Health app with a Longevity tab and Health Age was described as coming in a later software update and available in beta. Live Rewind and Siri Recap were described as expected later in the year, with beta timing. These dates and descriptions are time-sensitive; the review does not establish their current release status, so check Apple’s current software information before relying on availability.
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