Breathe at your resonance
and train your HRV

Slow, paced breathing — about five breaths a minute — tuned to the rhythm where your heart rate swings the most. Pair a chest strap, follow the circle, and watch your heart-rate variability respond beat by beat.

Start a session How it works

Works in Chrome, Edge, Brave or Android Chrome with a Bluetooth heart-rate strap. Free to start — no app to install.

What you get

A focused breath, measured precisely

One glowing circle to breathe with, and the live signal underneath it — nothing else competing for your attention.

Resonance pacing

A breathing circle expands and contracts at a slow, steady pace. Inhale as it grows, exhale as it shrinks — the simplest way to hold a five-breaths-per-minute rhythm without counting.

Live HRV, every beat

Heart rate, beat-to-beat change, and rolling RMSSD update in real time from your strap, with a heart-rate trace charting the rise and fall of each breath.

Find your resonance frequency

A guided assessment sweeps breathing rates from 4.5 to 6.5 per minute, scores the heart-rate response at each, and locks the pacer to your personal best.

Premium

Every session, tracked

Each session is saved with its HR trace, per-breath heart-rate range, and a full HRV scorecard — so you can watch your nervous system adapt over weeks.

How it works

Three steps to a session

1

Pair your strap

Connect a Polar H10 or any Bluetooth heart-rate strap straight from the browser — no app, no account needed to try it.

2

Breathe with the pacer

Set a session length and follow the circle. Hide every overlay for a pure, distraction-free breath whenever you want.

3

See your HRV

End the session for an instant summary, then sign up to save it and track your heart-rate variability over time.

Grounded in resonance-frequency breathing research. Breathing near ~0.1 Hz drives large, in-phase oscillations between breath and heart rate — the respiratory sinus arrhythmia that HRV biofeedback is built on. This app follows the protocols described in the peer-reviewed literature on resonance training.

Lehrer & Vaschillo · Shaffer & Meehan · Steffen et al. · Lalanza et al. (systematic review)

Before you start

  • A Bluetooth heart-rate strap (Polar H10 recommended).
  • A Chromium browser — Chrome, Edge, Brave, or Android Chrome — for Web Bluetooth.
  • iPhone and Safari are not supported (no Web Bluetooth); Firefox isn't either.

Find the pace your heart is waiting for

Pair your strap and run your first resonance session in under a minute.

Start training