Apple Watch Series 9 review: Why I'm not settling for the less expensive models

Apple Watch Series 9

4 / 5

Very good

pros and cons

Pros

• Health sensors are more accurate and more sensitive
• Screen brightness has doubled for better outside use
• Improved battery life now easily lasts a full day
• Double-tap gesture improves one-handed use

Cons

• No blood pressure tracking yet
• Valuable HRV data is only used by third-party apps
• Sleep tracking is still better with third-party apps
• The accuracy of Series 9 tracking calls older models into question

$407.57 at Amazon

This review was originally published on November 24, 2023, and was updated on September 4, 2024.

ZDNET's buying advice 

The Apple Watch Series 9 is powered by Apple's S9 chip, which makes the popular smartwatch faster, smarter, and better at reading your body signals -- based on my real-world tests next to the last-generation model (see below for full testing details). That makes the Apple Watch Series 9 a big step up. So, if you're in the market for an Apple Watch, I'd specifically recommend getting the Series 9 (or the Apple Watch Ultra 2) because the health tracking is such an improvement over previous models.

Also: Apple Watch Series 9 vs. Series 8: Which model should you buy?

If you have one of the Apple Watch models from the past few years and your watch is running perfectly fine, you don't need to get the Series 9. There aren't enough upgrade benefits to justify it for most people. If, however, you're coming from a Series 6 or earlier, and you wear the Apple Watch every day, then you'll likely see a lot of benefits by upgrading.  

If you're coming from a Fitbit or another fitness tracker and are purchasing your first smartwatch -- and nearly two-thirds of Apple Watch buyers are first-timers -- then you'll likely be very happy with how well the Apple Watch Series 9 can track your health, along with its other safety and convenience features. I strongly recommend getting the Series 9 over an Apple Watch SE or the Series 8 because it's notably better and more accurate at health tracking.

Also: ZDNET's Apple Watch buying guide

Specifications 

How I tested the Apple Watch Series 9 

I wore the Apple Watch Series 9 on my right wrist for a couple of months and wore the older Apple Watch Ultra on my left. At the risk of looking like a tech nerd -- and I did have numerous people ask, "Wait, are you wearing two watches?" -- I tested the accuracy, battery life, and performance of the latest Apple Watch while comparing it to the previous generation's tech as a baseline.

So, I tested both watches with planned and unplanned walks and workouts, including Fitness Plus sessions, tryouts of the new cycling features, and using various kinds of workout equipment in hotels while I was traveling. I also tested sleep tracking, stress tracking (HRV), breathing and mindfulness features, timers, new watch faces, and other built-in apps. I even tested the watches with some VR workouts by connecting them to the Supernatural app and the Meta Quest 3 headset.

What are the Apple Watch Series 9's best features? 

More accurate and more sensitive health tracking -- The Apple Watch remains a health and safety device above all else, and the new S9 chip inside the Apple Watch Series 9 makes it smarter and more accurate than ever. That was my unequivocal conclusion from two months of wearing the Series 9 on one wrist and wearing the older Apple Watch Ultra on my other wrist and comparing the data they captured and the responsiveness of their health sensors. (Remember that the original Apple Watch Ultra has the same base technology and sensors as last year's Apple Watch Series 8.)  

My testing revealed that the Series 9 was better at several things. It was faster and more accurate at prompting me if I began a walk, for example, but hadn't started a workout to track it. The Series 9 almost always triggered a workout prompt earlier than the previous generation, and sometimes triggered one (correctly) when the Apple Watch Ultra never triggered one at all. Another problem that I regularly had with both the older Series 8 and the first Ultra (and previous Apple Watches) was that they would sometimes lose track of my heart rate in the middle of vigorous workouts like runs, cycling, core exercise, and weight training. When that happened, the data for the workout would be thrown off and often become inaccurate.

As a result, I often had to notch the band tighter during these workouts, which became uncomfortable but did sometimes help to keep tracking my heart rate. Even then, both of the older devices (and previous Apple Watches before them) would occasionally still lose track of my heart rate in the middle of my workouts. The Series 9 did not have that problem even once during my period of testing -- even though I never tightened the band during vigorous workouts.  

Just as importantly, I found that when comparing data from workouts, the Series 9 nearly always reported different calorie-burning stats than the first Apple Watch Ultra, and often had different heart rate numbers as well. As you can see in the chart below, the numbers were off by 10% or more at times -- usually with the Series 9 reporting lower numbers. 

When I compared the numbers of both watches with workout equipment like treadmills and spin bikes (including different models in various hotels when traveling, and even when I entered my body stats into the equipment to make it more accurate), it appeared that the Series 9 data was closer to the true numbers. That's made me question whether older Apple Watch models are (inadvertently) inflating calorie-burning data. The bottom line is that my two-month test gave me more trust in the data from the Series 9 -- just as I also had more trust in the Series 9 to not lose my heart rate during workouts and better use its AI to start workouts when I forgot.

Brighter display for outdoor use -- The Apple Watch Series 9 display has a higher peak brightness: 2,000 nits instead of 1,000 nits. This matches the brightness of the Apple Watch Ultra (while the Ultra 2 has increased to 3,000 nits). This makes the Apple Watch even better to use in full sunlight, especially for outdoor activities like running, walking, hiking, cycling, and sports. At the same time, the display can now also dim down to 1 nit so that the always-on display draws less power.

True full-day battery life -- My biggest surprise was that the Apple Watch Series 9 has significantly better battery life even though it has a brighter display and a new, more powerful processor. Apple rated the Series 9 as having the same battery life as the Series 8 -- 18 hours (and 36 hours in low-power mode). 

In my real-world tests, I found that the Series 9 is actually quite a bit better. Sometimes the watch would have 60% battery left at the end of the day, even after I left the always-on display on and used the watch to track multiple workouts. Last year's Series 8 would typically have 30% to 40% battery left at the end of a similar day. I chalk up the battery life gains to the efficiency of the new S9 SiP processor and the ability of the always-on display to drop all the way to 1 nit of brightness.

These battery life gains also make it easier to wear the Apple Watch Series 9 at night for sleep tracking because you can simply put it on the charger for 30 to 40 minutes at the end of the day and then slip it back on before you go to sleep.

New double-tap gesture -- The new double-tap gesture allows you to more easily operate the watch with one hand. For example, if you have an incoming phone call and your hands are full, and you want to answer it with your watch, then you can raise your wrist and double-tap your thumb and forefinger together. 

The gesture is still limited to activating the most prominent action of the app you have open, but it will keep you from having to use your nose to tap the screen when your hands are full -- as many of us have resorted to for years. This is also reminiscent of the new thumb-and-forefinger gesture in the forthcoming Apple Vision Pro headset. So It feels like this is just the beginning, and perhaps even portends a future where the Apple Watch and Vision Pro work together. 

What I'd like to see in the next Apple Watch 

Better stress tracking using HRV -- The Apple Watch 4 introduced tracking of Heart Rate Variability (HRV), which is a newer health measurement that can be used to track your stress levels. For years, I've been using it to track my stress (I wrote about it on CNET in 2020) and I find it remarkably accurate. Unfortunately, you have to use third-party apps like HRV Tracker, Stress Monitor, or Welltory to tap into it on the Apple Watch.

Meanwhile, other devices such as Samsung's smartwatches track HRV and directly turn its readings into a stress score. You can trigger an HRV reading automatically on the Apple Watch by doing a "Breathe" session in the Mindfulness app, but Apple could do much better by making a separate stress or mental health app for the Apple Watch. This would fit perfectly with the new mood-tracking feature in WatchOS 10.

Blood pressure sensor -- High blood pressure (hypertension) is one of the most undiagnosed diseases on the planet and one of the most difficult to manage because it's so difficult to track with a standard blood pressure cuff. The result is that a lot of people end up with a high risk of heart disease, strokes, and other debilitating ailments. For years, tech companies have been working on ways to use mobile technology to measure blood pressure. That includes putting a finger over the camera on your smartphone paired with an app.

An even better option would be to have a smartwatch such as the Apple Watch passively monitoring blood pressure patterns and trends, as well as sending early-warning alerts when there are danger signs. Apple has reportedly been working on bringing blood pressure monitoring to its watch for years. Let's hope the wait is almost over. 

Blood glucose sensor -- Apple has also reportedly been working on integrating a blood glucose sensor, which is even more difficult than integrating a blood pressure sensor since today's blood glucose measurements involve drawing blood. First and foremost, this would help people with diabetes (over half a million globally) to manage this complex condition without having to prick their finger for blood many times a day. 

Even if you don't have diabetes, monitoring blood glucose can also have benefits for managing your health in other ways by offering insights into your diet/nutrition, energy levels, and when to schedule medicines, meals, and workouts. That said, we could still be years away from Apple and other companies bringing non-invasive blood glucose tracking to wearables such as the Apple Watch -- but it will be a big breakthrough when it happens.

Final thought 

Because of the generational technology leap with the Series 9, I'd recommend getting this model rather than the Apple Watch SE or the previous Series 8 or Series 7 models that you can still buy -- since the Series 9 technology will remain current for longer and is likely to benefit from future software upgrades for longer. The more sensitive and accurate health tracking sensors make previous Apple Watches feel outdated by comparison.

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