EasyBreath.work - Breath easily - online, free, quick
Multiple breah works for different use cases are available:
Heart Coherence: Calming
Box Breathing: Calming
Tummo (Wim Hof): Energizing
Breath Holding: Calming
Sleepy Breath: Calming
Bellow's Breath: Envigorating
Skull Shining Breath: Super Envigorating