Apple Watch Series 4 review

This smartwatch will save someone's life – and that's a claim few can make
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Apple Watch Series 4
By Apple
Just as Samsung, Google and the Wear OS gang look like they’re catching up to Apple, it goes and streaks ahead. The truth is that the Apple Watch Series 4 is in a different league right now, and balances style, features and specs to make an excellent smartwatch. Battery life is still just okay, and is the key reason to look elsewhere – as is the price which has crept up since the Series 3. The ease and availability of cellular, the accuracy and usefulness of its heart rate monitor and the breadth of its fitness ecosystem – these are the areas that have left rivals in its dust. Add Apple Pay, SOS, fall detection, the heart rate alerts – it’s incredible to think that the Apple Watch Series 4 will, undoubtedly, save at least one person’s life. And who else can say that right now?

  • Better design
  • Lifesaving metrics
  • Top sports features
  • More expensive
  • Battery life still short
  • Siri integration still not great

The Apple Watch keeps steaming on, and while its rivals try to make sense of the smartwatch form factor, the Series 4 arrives with the market wrapped around its little finger.

Yet the Apple Watch Series 4 is the company’s biggest change since the original Apple Watch landed in 2014. After four years and five watchOS operating systems, the design, features and use cases of the Apple Watch Series 4 have all shifted.

When the Apple Watch launched it was a device that simply validated the smartwatch form factor with its presence. Four years later it's dominating space, with the Series 4 showing us the direction the smartwatch will travel. That’s because Apple is now calling the shots – turning the smartwatch into a cellular, medical, and fitness device.

But does the Apple Watch Series 4 cut it? Here's our verdict on Apple's new smartwatch, and don't forget to check out our guide to the best smartwatches.

> Apple Watch Series 8 review

> Apple Watch SE (2022) review

> Apple Watch Ultra review

    Apple Watch Series 4: Design


    The Series 4 changes screen size for the first time since the original Apple Watch, and it now comes in 40mm and 44mm flavors, as opposed to 38mm and 42mm.

    It may sound like nothing, but millimeters make a difference in watches, and this shift makes for the best-looking Apple Watch yet. Losing the cavernous black gap around the edge of the screen makes for such a better looking smartwatch. Likewise, the newly steeper corners make for a less boxy look, and tellingly when you return to the Series 3 it just seems more… techy.

    Apple Watch Series 4 rivals: Samsung Galaxy Watch review | Fitbit Versa review

    For big wrists (namely men’s) the 44mm doesn’t feel overly large, and because it’s slimmer, it’s feels smaller than the old 42mm. And for men with slim wrists, the 40mm is also a decent option – go try one on for size if you’re unsure.

    But it’s a shame that the 38mm Apple Watch bought the farm.

    While the 40mm might not feel bigger (again thanks to the slimmer build making it smaller overall) and most people won’t feel the difference, the 38mm version was unique to the smartwatch world. It lives on via the Series 3 – but women, in particular, will need to cope with 2mm more screen estate than before to enjoy the Series 4.


    Watch Series 4 (left) next to Watch Series 3 (right)

    But there’s an upside – and that’s usability. The 38mm was always cramped, and the 40/44mm versions pack in 32/35% more screen real estate, aided by the edge-to-edge screen. The new features of the Apple Watch demand more on-screen information, so what’s been lost in the larger design should mean a better experience overall.

    And that’s part of the shift. The original Apple Watch was designed to be a glanceable companion, but the improved features – via cellular and heart rate data – mean it now requires more interaction than before.

    That’s embodied by the new Infograph watch face, which supports eight complications for a medley of on-screen information. The hero watch face for Series 4 is designed to push as much information as possible, and it’s a masterclass of presenting data in tiny spaces. But it’s telling how the use case of the Apple Watch has evolved over time.

    And it’s of course a matter of choice. If you want simple design, choose one of the new Fire and Water style watch faces. If you want max-detail, Infograph (below) is for you – with everything from key contacts, weather (with current, and daily min and max temperatures), activity rings, and even outside air quality all displayed on a single screen. We’ve fallen for Infograph in a big way.


    So, the new Apple Watch sizes will probably please more people – and though technically they’re all smaller in volume, they put more screen on your wrist. How you feel about that is a personal choice.

    Then there’s the improved speaker, which makes a big difference on the communication front. Anyone who’s taken a call from their watch (in the car perhaps) or used Siri might have found their Apple Watch pressed to their ear, but the new speaker is certainly louder and clearer – and you shouldn’t have any trouble making out what your contacts are saying via a call or a Walkie Talkie conversation.

    Apple Watch Series 4: Features


    So what’s going on in terms of the Series 4’s features?

    Well, we have the same basic functionality as Apple Watches of yore. Notifications, fitness tracking via the closing of the now iconic rings, sports tracking, and of course LTE cellular if you opt for the Series 4 LTE. Apple Pay still has a central role – and it’s still great.

    Read this: Essential Apple Watch tips and tricks

    We were satisfied by the Apple Watch Series 3 LTE experience once the kinks were ironed out – but it’s taking us time to really test how much the design changes have improved LTE. We’ll update you with our findings.

    There’s also a heap of changes courtesy of watchOS 5 – but these aren’t exclusive to the Apple Watch Series 4, and will land on all Apple Watch models bar the original. We have extensively outlined the changes in watchOS 5, and you can read them in our full watchOS 5 guides.

    Likewise, we’re still trying to trip hard enough for the Fall sensor to kick in. Perhaps it’s pleasing that the feature isn’t sensitive enough to produce false positives, but purposeful trips just aren’t setting this thing off. We’re working on it.

    Apple Watch Series 4: Health


    Along with cellular, it’s fitness and health features that Apple see as the biggest driver for the Apple Watch. And it’s a distinct difference – fitness refers to activity tracking and workouts, while health has much more serious connotations, in terms of monitoring your body for signs of illness, and protecting you against falls.

    Heart rate

    When the original Apple Watch landed it barely leveraged the heart rate sensor, but on the Series 4, it’s a key part of the experience. And there are multiple aspects.

    Read this: A complete guide to the Apple Watch heart rate monitor

    Heart rate is monitored 24/7 – and that data is used in a number of ways. First, you can view it on the Apple Watch itself by diving into the heart rate app. Then you’re presented with three sets of stats: resting heart rate, current heart rate, and walking heart rate. These are plotted across your day.

    We tested accuracy at rest against a chest strap – and found no discrepancies. And we double checked that against a good old pulse count with a stopwatch, which again checked out.

    It’s resting heart rate we like the best here, and it’s great to see this important stat tracked. And while the Apple Watch itself offers a great snapshot, the Apple Health app offers to track that’s as granular as you like – showing you resting heart rate plotted across day, week, month and year.

    Apple only takes a resting heart rate reading when it’s satisfied you’re at rest, having satisfied several variables from the accelerometer. Some competitors take resting heart rate when you wake up in the morning, which is probably the best experience, but as there’s no built-in sleep functionality, the Apple Watch can’t do that. Thus our resting heart rate was a few bpm higher than we’ve seen on Fitbit devices, but still a useful metric, and well presented.

    Heart rate notifications


    Part of the health features of the Apple Watch is monitoring your heart rate, and checking to see if anything is wrong. There are modes for high heart rate, which were introduced in watchOS 4, and now low heart rate and heart rhythm, which can be a sign of atrial fibrillation (Afib). This is a leading cause of strokes, which are in turn the second biggest killer in the US.

    You can set your low heart rate threshold in the Apple Watch app – with an all-out low level of 40 bpm. This should be good enough for most people, but there will be a subset of the super fit who regularly sleep below 40 bpm, so we wouldn’t be surprised to see 35 bpm and 30 bpm added soon.

    Essential reading: Why ECG on the Apple Watch Series 4 is such a big deal

    Then there’s the ECG functionality. Apple has added a titanium electrode on the sapphire and adapted the digital crown, so the Watch can take an ECG reading from your finger. A 30 second reading from the ECG app will do two things: first, assess whether your heart rate is normal (Sinus) or Afib. Finally, it will spit out an ECG graph of your heart rate into the Health app, which can be given to your doctor.

    Interestingly, it’s this aspect that the FDA has certified – and has real world benefits. The idea is that those with heart conditions can take an FDA certified reading of their heartbeat, perhaps when they’re feeling unwell, rather than during a medical appointment, when everything may be reading normal. And it moves beyond Afib, with an ECG useful for diagnosing a huge range of complaints.

    The feature lands in the US later this year, and we haven’t yet had chance to test the feature personally, although we were treated to a demonstration by Apple. What it represents, however, is the Apple Watch moving beyond a smartwatch into a true medical device. What’s more, this functionality isn’t an extra – and while (hopefully) most people will never need it, or see high/irregular/low warnings, it will save lives. And there are few wearables out there that can make that claim.

    Activity tracking


    The activity-tracking elements of the Apple Watch haven’t hugely changed, and it’s still a great experience for those wanting to keep tabs on goals. For the uninitiated, you need to close three rings: Move (calories) Exercise (active minutes), and Stand (the amount of hours in which you’ve stood for a single minute).

    Essential reading: Apple Workout and Activity apps explained

    It’s a nice break from the standard step goals, which are the preserve of most fitness trackers – and the closing of the rings is a great way to express your progress. The rings can also be added as complications, so you can see three goals worth of progress in a very small space – which is clever stuff.

    What’s more, the Move goal automatically shifts according to your general activity, so it doesn’t seem overbearing or too easy and grows as you get fitter. A big thumbs up here.

    You’re still prompted to stand, which can be a little irritating, but that’s not as annoying as the reminders to use the Breathe app – Apple’s mindfulness play. It’s simply an app that guides you through a breathing routine, which supposedly relives stress. The reminders are quite off-putting, and we quickly turned this off in the app.

    You can review all goal progress on the Watch from the complication, the Activity watch app, the special Activity watch face, the regular updates and prompts, and get historical goal progress via the Activity iPhone app.

    One of the most common questions we get about the Apple Watch is sleep – and this still isn’t tracked natively within the watchOS experience. This means you’ll still be relying on third party Apple Watch sleep apps – which can offer a decent experience – but is a hole within the 360-degree picture of your health that the Apple Watch generates.

    Apple Watch Series 4: Sports tracking


    Workout app

    While the workout app hasn’t changed for the Series 4 per se, it’s undergone substantial improvement in watchOS 5 – and that’s crucial if Apple wants to convince sporty types to move away from Garmin.

    Read this: Best Apple Watch apps to download first

    So there are new sports tracked, with the full list reading running (indoor and outdoor), cycling (likewise), walking (indoor and outdoor), hiking and yoga (both new to watchOS 5) plus rowing, elliptical, stair stepper, and general high-intensity interval workouts.

    It will now automatically detect exercise – so if you forget to start the watch, it will pick up your workout. It worked for walking and running – but can kick in quite slowly. It won't pick up a supposed workout until around 10 minutes of sustained activity - but when it did, we didn't have any issues with missed minutes. It came out exactly in line with a Garmin that was tracking our run from the beginning, which was highly impressive.



    Running is the area that’s been improved most, with some specific metrics added. watchOS 5 adds a bunch of new workout features, including auto-exercise detection as well as cadence and rolling pace. We’re excited to see cadence added to the Workout app, which is an underused stat for running efficiency, and our tests generally saw its shape up to Garmin’s estimates.

    There is a snag, however. The Apple Watch only supports one screen of in-workout data, so you have to select the metrics you want in the Apple Watch app. There are six slots taken by duration, heart rate, rolling pace, average pace, and distance. If you want to add another metric – e.g. cadence – you’ll need to sacrifice one of those.

    It’s not ideal, and coming from the wealth of in-workout data you’d get from a Garmin, for example, it feels a little limiting. When running 10-20 miles, you have time to indulge yourself with stats, and it would be nice to get more data. A second screen of info isn’t too much to ask.

    Likewise, the review of runs from the Workout app isn’t superb. They’re listed in the Activity iPhone app, but there’s little macro analysis of your progress.

    Of course, there’s also the world of third-party apps. Pretty much every service is catered for, including Strava, which offers all the macro analysis any runner or cyclist needs. If you’re someone who feels the Workout app experience is undercooked, third party apps can pick up the slack.



    Apple introduced swim tracking to its smartwatch with the Series 2 and while it hasn't made any wholesale changes with the way the Series 4 performs in the water, that's not necessarily a bad thing.

    Outside of usual sports watch suspects from the likes of Garmin, Polar, and Suunto that track swimming, the Apple Watch does a good job here. We'd say it's comfortably the best smartwatch you can grab for a swim.

    Once you've got an appropriate band strapped on, it's supremely light and comfortable to wear. The lack of an always-on display mode sounds it should be a nightmare when you need to check in on performance, but the sensitivity of the raise-to-wake feature to activate the display works well here. The use of bright text colors to display swim data set against the black screen is a great combination in terms of soaking up metrics during a swim and improving visibility underwater.

    In terms of accuracy, we were happy with what the Series 4 served up against a top end Garmin sports watch too. Core data (distance, lap counts, average pace) were all pretty much in line with the data recorded by the Garmin Forerunner 935 we put it up against and there was nothing in the data to raise concern over.

    Data of course lives in the same place, but you do have a bunch of Apple Watch swimming apps to play around with as well. Bottom line, if you want an Apple Watch to track performance in the pool (or open water), you should be pretty happy with what the Series 4 serves up.

    Heart rate during exercise


    We’ve been impressed by the accuracy of the heart rate sensor on the Apple Watch since the first generation – but the Apple Watch is now a leader when it comes to optical accuracy.

    We’ve put the Apple Watch through the same series of tests we subject the likes of Garmin, Polar, and Suunto to – and it produced one of the best accuracy performances we’ve seen.

    Through a medium-intensity run, the optical sensor was locked onto that of a Garmin chest strap paired to a Fenix 5 – almost beat-for-beat. Pushing through five miles of running, into and above the threshold, the Apple Watch was never more than 1 bpm out, and over 40 minutes of exercise, plus interval sprint finishes, the two produced identical average bpms.

    The sprint intervals involved letting heart rate settle at around 120 bpm and then sprinting for 100m, raising the heart rate to around 185bpm. This will temporarily bork most sensors, with the quick escalation of heart rate exposing lag times between sensor and watch. What’s more, sprinting in this manner causes mass movement noise, further scrambling optical sensors.

    Now, the Apple Watch wasn’t perfect – it’s not solved the optical sensor problem. But in a sprint interval session, it followed the chest strap up to the exact peak HR, around five seconds after. It also tends to increase in large stages, but the critical thing is that it does get to those HR peaks, while rivals are often still rising while your heart rate is falling after an interval.

    Typically, the decrease in heart rate during rest also fell slower than the chest strap, but better than on devices such as the Suunto 9 and Fitbit Ionic which we’ve recently reviewed.


    The details are above, though they aren’t too easy to compare visually, partly because of the slightly basic way that Apple presents data from the workout app – which goes back to our previous criticisms of the Workout ecosystem.

    The verdict here is that Apple is leading in optical accuracy, and while it’s far from perfect, buying a Garmin or Fitbit watch/band won’t get you better optical performance. However, the caveat is that if you’re concerned about your heart rate from your CrossFit class, you might want to invest in a Bluetooth chest strap, which works with the Apple Watch Series 4.

    Apple Watch Series 4: Siri


    Part of the logic behind adding a louder speaker was enabling better interactions with Siri – but this is still a mixed bag.

    Siri still isn’t a leading smart assistant – but it’s improved a lot. Siri on the Apple Watch is great for setting alarms, quick reminders, checking the weather, and running quick internet searches with your voice.

    We could dedicate an entire review to Siri itself, but actually running some tests, we were surprised at the number of searches it returned. “When is the Ryder Cup?”, “how do you spell renaissance?”, “how many milliliters in a cup?” – it works quite nicely.

    When things got a bit more complicated, it did fall somewhat. Mapping and directions are still a bit of a pig, when going from the watch. Siri is easily flummoxed by background noise, and garbles searches of things like business names: “Howdens Beckenham” was consistently turned into “how did this back in him”. “Direct me to Norwood Junction” (a local train station) just sent me to a place called Norwood 4.5 hours away.

    A new feature in watchOS 5 is the Siri wrist raise that lets you just pull the watch to your mouth, and ask Siri a question Dick Tracey style. We found it a tad hit-and-miss with the wrist raise – particularly if you need to make a second query. You had to exaggerate the action of returning your hand to the side, then raising the wrist again.

    Apple Watch Series 4: Battery life


    If there’s going to be one major gripe with the Apple Watch Series 4 in the comments below, it will be about battery life. Despite adding 2mm to the screen size (and slimming the case), battery life remains at 18 hours.

    In real world tests, we’d find our watch at around 50% drain when heading to bed – so with some careful management you could get it through two “days”. But those calling for a week of battery life are going to be disappointed. If you’re going on a three-day city break or business trip, remember to pack that charger.

    Our running and sports tests also agreed with Apple that you should get around six hours of GPS tracking – so more than enough to complete a marathon. That part we have no issue with.

    In the era of smartphones that require nightly charging, we don’t have a huge problem with the Apple Watch only lasting a day. The reality is that to get more longevity, design, and features would have to be culled – and the Series 4 would be a very different smartwatch.

    But packing that extra charger for a weekend is annoying – and it’s a legitimate reason that will see people look to something like the Fitbit Versa instead.

    How we test

    James Stables


    James is the co-founder of Wareable, and he has been a technology journalist for 15 years.

    He started his career at Future Publishing, James became the features editor of T3 Magazine and and was a regular contributor to TechRadar – before leaving Future Publishing to found Wareable in 2014.

    James has been at the helm of Wareable since 2014 and has become one of the leading experts in wearable technologies globally. He has reviewed, tested, and covered pretty much every wearable on the market, and is passionate about the evolving industry, and wearables helping people achieve healthier and happier lives.

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