Check your heart rate with your phone camera
Rest a fingertip over the rear camera for about 25 seconds. The page reads the tiny colour change each heartbeat causes and shows your pulse in beats per minute, or tells you honestly that it could not get a clean signal.
Camera pulse reader
Press start, allow the camera, then cover the lens with a fingertip.
On Android phones the flash switches on by itself. On iPhone, sit next to a bright lamp or window.
Saved on this device
How to get a clean reading
- Sit down and rest first. For a resting value, sit quietly for a few minutes; MedlinePlus suggests at least 10 minutes of rest before measuring a resting heart rate[1].
- Steady the phone. Lay your hand and the phone on a table instead of holding them in the air.
- Cover lens and flash together with the soft pad of one fingertip. The preview circle should turn an even red.
- Press lightly. Pressing hard squeezes blood out of the fingertip and flattens the signal; resting the finger is enough.
- Hold still and breathe normally until the ring is full. Talking and fidgeting show up as noise.
Cold hands give a weak signal because less blood reaches the skin. Warm them up first. If the picture looks dark, add light; if it looks white rather than red, ease off the flash a little by shifting your finger.
What the page actually measures
With each heartbeat a small pulse of blood pushes into the fingertip. Blood absorbs light, so the frame gets very slightly darker on every beat and recovers between beats. The change is around one percent of the brightness, invisible to the eye but easy for software to follow. This technique is called photoplethysmography; it is the same idea a clip-on finger sensor uses, with your phone’s camera and flash standing in for the sensor.
About 30 times a second the page shrinks the middle of the camera image to a few hundred pixels and averages them. Those averages form a wave. A filter keeps only the rhythms between 42 and 210 beats per minute and removes slow drift from breathing and pressure changes. Then two independent estimates are made: one finds the strongest repeating frequency, the other finds individual beats and measures the gaps between them. If they agree, the rhythm is steady and the signal stands out from noise, you see a number together with a signal-quality label. If not, you see the reason and a suggestion instead.
The first four seconds are discarded while the camera adjusts its exposure, and the next 20 seconds are analysed. Lifting the finger for more than a moment restarts the run, so two separate placements are never stitched together.
How close is a camera reading?
Fingertip camera apps have been compared with ECG in published studies. In 108 hospital patients, the two finger-on-camera apps tested correlated with ECG at r = 0.83 and 0.96, with average absolute errors of about 2 to 4.5 beats per minute, while apps that read the face from a distance did clearly worse[2]. A meta-analysis of 14 studies found an average difference from reference devices of −0.32 bpm, with limits of agreement within 10 bpm, but only in resting adults with a normal rhythm[3]. The same review notes that readings may be less dependable during an irregular rhythm, with movement or poor light, and that children were not studied.
whatsmypulse uses its own analysis code. It has been tested against synthetic signals with known rates, where every reading it shows lands within 3 bpm and noisy signals get no number at all, but it has not been tested in a clinical study. Treat it as a handy estimate, not a measurement to make health decisions on.
Your camera stays private
No frame, photo or video is stored or sent. The page is delivered with a Content-Security-Policy whose connect-src 'self' rule lets the browser talk only to whatsmypulse.com, and the measuring code does not talk to anything at all. To check it yourself, open your browser’s developer tools, choose the Network panel, and start a measurement: no request appears while the camera runs. Saved readings, if you choose to save them, stay in this browser’s storage and can be cleared with one button. Details are on the privacy page.
iPhone and Android notes
- Android with Chrome: the page asks the camera to turn its flash on, which gives the strongest signal. If a phone opens a rear lens without a flash, the page tries the other rear cameras.
- iPhone and iPad: browsers on iOS may not let a web page switch the flash on, so measure next to a bright lamp or a sunny window and let the light shine through your fingertip into the lens.
- Firefox: it does not offer flash control to web pages at all; use bright light the same way.
- Opened inside a social or chat app? In-app browsers often block the camera. Open the page in Safari or Chrome instead.
Prefer not to use the camera? The tap counter works on any device without permissions, and the classic count-for-30-seconds method is built in there too.
Questions people ask
Does the video leave my phone?
No. Each frame is shrunk to a tiny square, averaged into three numbers (red, green, blue) and dropped. The page’s security policy only allows network connections back to whatsmypulse.com, and the measuring code makes none. You can switch to airplane mode after the page loads and it still works.
Why does it sometimes refuse to show a number?
Because a wrong number is worse than none. Two separate methods estimate the rate from the same signal, and the result is shown only when they agree and the rhythm stands clearly above the noise. Moving, pressing hard, cold fingers or dim light are the usual reasons for a refusal.
Can I use the front camera or a laptop webcam?
It can work with a bright lamp shining through your fingertip into the lens, but the rear camera of a phone with the flash on gives a much stronger signal. Without a flash, expect more retries.
Can this check my heart rhythm or blood pressure?
No. This page estimates one thing, your average pulse rate over about 20 seconds. It cannot detect or diagnose any heart condition, and it does not estimate blood pressure or oxygen levels.
Why is my camera reading different from my watch?
Different devices sample at different moments and average over different windows, and your pulse changes from minute to minute. Studies of fingertip camera apps found readings at rest close to ECG on average[3], but any single reading can be off by several beats.
The flash got warm. Is that normal?
The LED does warm up when it stays on. A measurement lasts under half a minute and the light switches off as soon as it ends. Stop if it gets uncomfortable.
Sources
- MedlinePlus (U.S. National Library of Medicine). Pulse (review date Jan 1, 2025). medlineplus.gov. Checked 2026-10-09.
- Coppetti T, Brauchlin A, Müggler S, et al. Accuracy of smartphone apps for heart rate measurement. Eur J Prev Cardiol 2017;24(12):1287–1293. doi:10.1177/2047487317702044. Checked 2026-10-09.
- De Ridder B, Van Rompaey B, Kampen JK, Haine S, Dilles T. Smartphone apps using photoplethysmography for heart rate monitoring: meta-analysis. JMIR Cardio 2018;2(1):e4. doi:10.2196/cardio.8802. Checked 2026-10-09.