Xiaomi Watch S4 review - a good watch for the money

Xiaomi has had more success with bracelets so far. Success with watches has always eluded them. A big reason for the failure was the WearOS system, with which they never managed to overcome the problem of battery autonomy. For the new Xiaomi Watch S4, they decided to install their own HyperOS 2 system, which should have no problems with this. What about the rest of the equipment? Is it good enough for just under €200? Are other smartwatches still better?

Xiaomi Watch S4 – I can't talk about the appearance at length

At first glance, the Xiaomi Watch S4 makes a positive impression with its classic round shape and relatively high-quality workmanship. The watch case is made of aluminum alloy with a special PVD coating that gives it the look and shine of stainless steel. The bottom of the watch (back), which is in contact with the skin, is made of black ceramic - a material that is appreciated in the world of smartwatches for its hypoallergenicity, durability and elegant appearance. The watch is relatively larger (case dimensions 47.3 × 47.3 × 12.0 mm) and weighs about 44.5 grams without a strap. When I look at it, the screen case seems quite concrete, and on the wrist it feels just fine, although not as balanced as on others.

Can it serve as a fashion accessory? Personally, I don't think so. I wouldn't rank it among the most beautiful smartwatches, especially not with the white and silver strap. The black one looks better in the pictures, but not by much.

What stands out about the new Xiaomi Watch S4 is the replaceable bezel (the frame around the screen). If you squeeze and twist it, you can remove it and replace it with another one. I support this innovation and I think it's a very simple idea to adapt the watch to your style. However, I'm surprised that additional bezels are not sold in the Slovenian Xiaomi store. I found them immediately in other countries and I like the blue-gray combination of the strap and bezel the most. I just have a hard time digesting that I have to pay an additional €50 for it, or a third of the value of the watch.

The default case is available in basic black or silver-white (my test version), while the special "Rainbow" version includes a colorful bezel and an additional strap. The side of the watch is adorned with a rotating crown surrounded by a decorative pattern, and an additional button for controlling the watch.

The watch is also waterproof up to 5 ATM, which means it can withstand swimming and showering (up to 50 m depth), but hot baths and diving are not recommended with it on your wrist.

The screen is excellent and bright

The display is one of the strongest points of the Xiaomi Watch S4. It uses a 1.43-inch (3.63 cm) AMOLED display with a high resolution of 466 × 466 pixels, which at this size corresponds to a density of 326 ppi. The image is therefore very sharp, individual pixels are practically indistinguishable, which is basically the case with all smartwatches.

The screen refresh rate is 60 Hz, which contributes to a smooth display of animations and menu navigation. For watch standards, 60 Hz is quite enough. It is only important that the chip can keep up with our use and fast refresh, and it did. The colors on the AMOLED screen are vivid, the animations are clear. With such a small screen, it is difficult to comment on its excellence compared to other watches. As long as the manufacturer does not skimp on the panel, almost every user will be satisfied with the displayed image.

Another important advantage of the screen is its brightness. Xiaomi states that the Watch S4 reaches an average of 1500 nits of brightness and even up to 2200 nits in automatic mode. In practice, this means excellent readability outdoors in bright sunlight. In direct sunlight, the screen was mostly clear, with occasional reflections. The screen supports always-on display (AOD), which can display the time and basic information at all times, although this feature does, as expected, increase battery consumption slightly.

This time HyperOS 2 instead of Wear OS

As mentioned, this time it is running HyperOS 2. This means that it does not use Google's Wear OS or any other universal platform, but rather a dedicated software tailored to the Xiaomi ecosystem. The hardware base (processor and RAM) has not been officially disclosed.

Despite the unnamed chipset, the watch works responsively and smoothly in practice. Navigating through menus, opening applications, and on-screen animations are all done without noticeable delays. This is also helped by the optimized HyperOS 2, which in this generation has been upgraded with a more refined user interface and support for a rotating crown for scrolling through content. The user interface feels more mature and refined than in the previous generation, which is reflected in the nicer graphic elements, clear widgets, and a more intuitive display of notifications.

The Xiaomi Watch S4 works with both Apple and Android devices. I can't comment on whether there are any restrictions for Apple users, so I recommend that you browse user reviews before purchasing.

It bothers me that you absolutely need the Mi Fitness app to use it. Bluetooth connection alone is not enough, you have to pair the watch in the app. But I expected Xiaomi to lock certain features into its ecosystem. For example, hand/finger gestures work on all Android devices (including Huawei), although many manufacturers lock such features and enable them only on their own brand devices (for example, Samsung).

It should be noted that the Xiaomi Watch S4 does not have a classic app store, as we know from some competing watches. The user is limited to pre-loaded applications: clock, calendar, alarm, stopwatch, weather forecast, calculator, music player, control of music playback on the phone, compass, exercise app, breathing exercises, etc.

However, the ability to install any additional third-party applications is missing - unlike smartwatches with Wear OS, we will not find Google services here (Google Maps ...). Xiaomi promises improved support for third-party providers, but there is currently no real ecosystem of independent applications on the watch itself.

Will this be a hindrance? It would be nice to have the option to integrate with Strava or the Komoot app, especially if you're already used to it. They may add this in the future, but right now it's a shortcoming of the system.

In addition to the touchscreen, the watch is controlled by the aforementioned rotating crown, which allows you to browse menus and messages, and a side button, which only serves as a shortcut to settings. Unfortunately, you can't customize it to, for example, guide you to workouts or other measurements. Also new are hand gestures (turn/shake your wrist, clap your fingers) to reject a call, open the Weather and Camera apps, and the like.

A bunch of sports and health metrics

One of the main tasks of a smartwatch is to monitor the user's health and activity - the Xiaomi Watch S4 offers plenty of functionality in this area. Numerous sensors are built in: an optical heart rate sensor (which can also measure blood oxygen saturation, SpO₂), an accelerometer, a gyroscope, a light sensor, an electronic compass, a barometer and a Hall sensor. In short, all the sensors that we are used to using on watches.

During the day, it will monitor your heart rate, blood oxygen saturation, sleep, stress, etc. There are no more advanced measurements such as an ECG. For measurements that are important to us (steps, heart rate, etc.), it is relatively accurate, with deviations in the range of 5 %, which is acceptable for a smartwatch.

There are over 150 different sports profiles available: from the common ones like running, walking, cycling, swimming, yoga, to more specialized ones like hiking, skiing, rowing, and even a few unnecessary ones like chess and kite flying.

The watch is water resistant up to 5 ATM, so it is also suitable for swimming. It has a special swimming mode that tracks distance, time, calories and detects swimming stroke types. For runners, the Watch S4 is particularly interesting: it includes a personal running coach on the wrist, which offers guided running programs (e.g. for beginners or to improve endurance) and displays data such as pace, distance covered, heart rate and heart rate zone in real time. Advanced runners will appreciate additional running form metrics - the watch can automatically recognize parameters such as cadence, vertical oscillation, ground contact time and the like, and based on this data, offers tips in the application for improving technique. VO₂ max, training load and recovery assessment are also calculated, which helps in planning training and rest.

The built-in GPS module on the Watch S4 is another important element for sports enthusiasts. The watch has a dual-frequency GNSS receiver (L1 + L5), which supports five satellite systems: GPS, Galileo, GLONASS, BeiDou and QZSS. Dual-frequency technology means more accurate and faster positioning, even in more demanding conditions (for example, among the Ljubljana skyscrapers or in the forest). During testing, the watch quickly established a GPS signal and tracking the route was accurate, comparable to other watches.

The 486 mAh battery offers above-average autonomy. Officially up to 15 days, but in practice up to somewhere between 7-9 days, depending on how often you use GPS and the always-on display.

Xiaomi Watch S4 – not bad, but again, it doesn't stand out

The relatively low price (€179) doesn't always come to its aid. It doesn't deserve much praise. It does basic measurements well, the replaceable bezel is a unique feature (albeit expensive), the screen is good, and the battery is finally long-lasting.

But for the same or similar price you can also get, for example, the Huawei Watch GT 4 or 5, which are more beautiful and powerful watches.