Allow the camera to begin. Nothing is recorded or sent anywhere.
Signal confidence—
Perfusion—
Beat spacing—
Variability (RMSSD)—
Session low / high—
Frame rate—
Turn the camera back on
Getting a clean reading
Rest the pad of your index finger flat over both the lens and the flash. Cover them completely.
Press lightly. Hard pressure squeezes the capillaries and flattens the waveform.
Keep the hand still and supported. Motion is the main source of bad numbers.
Give it about eight seconds. The reading stabilises once the chart shows a repeating beat.
No flash on your phone? Point the lens at a bright lamp with your finger between them, or switch to the green channel in daylight.
The chart is the raw optical signal after a 0.7–3.5 Hz bandpass. Each dot marks a detected beat. Rate comes from the autocorrelation of a 10-second window, not from counting dots, so single missed beats do not move the number much.
Not a medical device. Readings are an estimate from ordinary phone optics and can be wrong, especially with cold hands, motion, or an irregular rhythm. Nothing here leaves your phone — no video is recorded or uploaded.