What Is the Light Level Around You?
Measure the ambient light level around your device in lux using the built-in light sensor. Monitor brightness changes in real time for display calibration or workspace assessment — all processed locally in your browser.
This test reads the device's ambient light sensor via the AmbientLightSensor API, reporting illuminance in lux with real-time updates to show how environmental light levels change over time.
A typical office is 300–500 lux, direct sunlight reaches 100,000 lux, and a moonlit night is about 0.1 lux. Display auto-brightness uses this same sensor to adjust screen level.
What Do Your Results Mean?
| Result | Range | Meaning |
|---|---|---|
| Good | 300–500 lux (typical office or well-lit room) | Your environment has comfortable lighting for screen use. Auto-brightness should function well, and eye strain risk is low at this level. |
| Warning | Below 100 lux or above 1,000 lux | Low light may cause eye strain if screen brightness is too high relative to surroundings. Very bright environments may make screens hard to read — consider adjusting screen brightness or repositioning. |
| Poor | Sensor unavailable or reading 0 lux consistently | The Ambient Light Sensor API may not be supported in your browser or on your device. Chrome requires enabling the Generic Sensor Extra Classes flag. Some devices lack a dedicated light sensor. |
Common Issues & Solutions
Sensor not available or permission denied
The Ambient Light Sensor API requires HTTPS and may need a browser flag enabled. In Chrome, navigate to chrome://flags and enable 'Generic Sensor Extra Classes'. Firefox does not support this API. Grant sensor permissions when prompted.
Readings stay at 0 or do not change
Your device may not have a dedicated ambient light sensor, or a case or screen protector may be covering the sensor. Check your device specifications and ensure nothing is blocking the sensor area near the front camera.