WHOOP 4.0 is built around one idea: recovery drives performance. There's no screen, no notifications, and no distractions — just continuous, always-on data working quietly to tell you exactly how hard to push and when to rest.

At 33% smaller than its predecessor, the 4.0 sits comfortably on any wrist size without getting in the way. Five LEDs — green, red, and infrared — capture heart rate, HRV, respiratory rate, SpO2 (blood oxygen), and skin temperature continuously, day and night. The Health Monitor consolidates all your key vitals into one dashboard and alerts you when any metric strays from your personal baseline.

Sleep Planner with haptic alerts gives you a silent alarm with three modes: wake at a set time, wake when you hit your sleep goal, or wake when your recovery is at its peak. Any-Wear Technology lets you move the sensor off your wrist entirely, wearing it on the torso, bicep, calf, or waist via WHOOP Body smart apparel.

The waterproof battery pack slides on over the device for on-the-go charging without ever removing the tracker. Hardware is included free with a WHOOP membership.