O2
iOSBreath-hold training app with guided breathing exercises and tolerance tables.
Download on App Store
Breath-hold training app with guided breathing exercises and tolerance tables.
Download on App StoreScreenshots
O2 is your personal breath-hold coach. Whether you're a freediver, surfer, or just curious about breathwork, our scientifically-designed training tables help you safely build CO2 and O2 tolerance over time.
Track your personal bests, log mindfulness minutes to HealthKit, and watch beautiful particle animations guide your breathing. Comprehensive safety features and health warnings ensure you train responsibly.
Training Phases
Prepare & oxygenate
Build tolerance
Rest & prepare
Features
Progressive training tables that adapt to your personal best, building tolerance safely.
Navy SEAL 4-4-4-4 technique for stress relief and focus enhancement.
Automatically log mindfulness minutes from your breathing exercises to Apple Health.
Train with your eyes closed using haptic feedback and voice guidance.
Particle-based breathing ring with smooth color transitions and calming feedback.
Train anywhere, anytime — no internet connection required.
Breath-hold training carries inherent risks including hypoxia and loss of consciousness. Never practice in or near water without supervision. For users 18+ or with parental consent (13-18).
Built With
Start your breath-hold training journey today. Free to download with optional Pro upgrade.