Photoplethysmography (PPG) is a method to assess blood flow and other clinical parameters by measuring light absorption and reflection of the skin. Remote photoplethysmography (rPPG), in particular, uses a camera, such as a webcam, for this purpose. Surprisingly, it actually works.

Below is a simple application that demonstrates this capability. What may be remarkable is that this application uses only the native capabilities of the Web browser, and requires well under 400 lines of code, HTML + CSS + JavaScript. This little implementation is entirely self-contained, without relying on any third-party code or library.

Needless to say, you need a Web cam for the app to work, and you must grant permission to use the camera when the browser asks for it.

The software likely works in all recent Chrome-derived browsers and the latest Firefox; may fail with other browsers. Note that this is a technology demonstration, not a clinical tool. The measurements are uncalibrated, "proof-of-concept", not necessarily accurate. No information is transmitted over the Internet: the measurement and its evaluation take place entirely within your Web browser's context on your own local device.