When web browsers sense light close to you

Ambient Light Sensor tells web sites about lighting conditions in your surrounding. I describe the privacy issues of ambient light sensors in my analysis.

Example below currently works best with a modern hardware such as Android device with Firefox Mobile browser or laptops such as Mac Book Pro. Ambient Light Sensor readout is related to user's activity, such as:
  • Surrounding light change
  • User's position in front of a device. Are you sitting there at all? Ambient Light Sensor is a perfect proximity sensor
  • Sensing the direction and mechanics of user's motion, relative to light sources
The sensor is usually physically located in your devices' upper region; try moving your hand close to it. If your device has a sensor and your browser supports it, you will see how the readout changes below (otherwise try Firefox Mobile on Android to get a feeling). Providing more than 50 light events would best help in this privacy study.
Min/Max illuminance:

Min/Max time between consecutive events:

Event count:

Illuminance readout change

Numbers of same illuminance events. Sensors sometimes repeat a particular value of illuminance.

Proportion of readout of different type

Raw readouts below: