Design & Build Quality
The Xiaomi Watch S4 is a 47mm aluminum smartwatch that weighs just 44.5g, making it one of the lightest watches in its size category. It supports standard 22mm straps, opening the door to a huge ecosystem of third-party options — from leather to silicone and ballistic nylon.
But the headline feature here is the bayonet-style interchangeable bezel, which securely locks in place. Unlike its predecessor (Watch S3), the Watch S4 now includes a vibration alert when the bezel is removed to avoid accidental loss — a smart and practical upgrade.
Display & Controls
This is where the Watch S4 truly shines. Its 1.43-inch AMOLED display with 466x466px resolution and 2,200 nits peak brightness is sharp, vibrant, and easily visible even under direct sunlight. Xiaomi’s watch faces are beautiful and optimized for Always-On Display (AOD) mode, though most default to black for battery efficiency.
The rotating crown with haptic feedback is a great addition for navigation, paired with a secondary button for quick toggles. Unfortunately, these physical controls aren’t remappable. The UI relies on vertical swipes rather than horizontal panels, giving it a clean and focused feel.
Smart Features & OS
Running HyperOS 2, the Watch S4 provides a seamless interface with Xiaomi Smart Hub and Mi Fitness. Navigation is fluid: the crown opens the app grid, swipes show widgets and notifications, and a dedicated button opens quick toggles.
Gesture control is included (e.g., wrist flick, finger snap), though it’s not always reliable. Notifications are basic — you can read and dismiss them but not reply. Emoji support is limited, especially in third-party apps like Messenger.
Fitness & Sleep Tracking
With 150+ workout modes, dual-band GPS (L1 + L5), and accurate heart rate tracking, the Watch S4 is a solid fitness companion. GPS lock takes ~40 seconds and delivers accurate route data.
Sleep tracking is rich in insights — including sleep score, personalized feedback, and even a “sleep animal” theme. However, the data seems overly generous, especially for deep sleep durations, which may not match data from more established trackers like Galaxy Watch or Huawei GT series.
Battery Life & Charging
Xiaomi claims up to 15 days of usage, but in testing with AOD and notifications on, plus an hour of daily workouts, battery life averaged 2 full days — 3 days max. Disabling AOD and sleep tracking can stretch this further.
Charging is handled via a 2-pin USB-A magnetic charger, which is finicky compared to competitors like Samsung or Huawei that use more stable solutions.
