Each heartbeat pushes blood through your fingertip, subtly changing how much light it absorbs. The rear camera (with its flash, if available) records these changes — photoplethysmography (PPG). Every panel here is derived from that one signal.

• Cover the rear camera and flash completely with the pad of a finger.
• An index or middle finger usually gives the strongest signal; either hand is fine. Coverage and stillness matter most.
• Hold still for ~15 seconds; warm hands read better than cold.
• If the image keeps switching, pick a single Lens (on iPhone, Back Ultra Wide).

For wellness and curiosity only. This is not a medical device and the derived figures are indicative, not a diagnosis.