Ambient Light Sensor
Measure your environment's brightness using your device's light sensor.
How to Use This Test
- Open this page on a device with an ambient light sensor (most smartphones and some laptops).
- Grant permission if your browser requests access to sensor data.
- Move your device between different lighting conditions (bright light, shade, dark room) and observe the lux readings change in real time.
What This Test Checks
This ambient light sensor test reads data from the Ambient Light Sensor API to measure the illuminance of your surrounding environment.
- Whether your device has a functioning ambient light sensor
- Real-time lux readings reflecting your current lighting conditions
- Sensor responsiveness when transitioning between different light levels
- Browser compatibility with the Ambient Light Sensor API
Troubleshooting
If you're having issues with the ambient light sensor test:
- Use Chrome on Android and enable the "Generic Sensor Extra Classes" flag in chrome://flags for best compatibility.
- Make sure no case or screen protector is blocking the light sensor, which is usually near the front camera.
- Safari and Firefox currently do not support the Ambient Light Sensor API.
- If the sensor reads zero or a fixed value, restart your device to reset the sensor hardware.
Frequently Asked Questions
Why isn't the ambient light sensor working in my browser?
The Ambient Light Sensor API has limited browser support and is often disabled by default for privacy reasons. Currently, Chrome on Android supports it when enabled via browser flags. Safari and Firefox do not support this API. Check chrome://flags for the "Generic Sensor Extra Classes" flag.
What is lux and how is it measured?
Lux is the standard unit of illuminance, measuring the amount of visible light falling on a surface. A dark room is typically under 50 lux, an office is 300-500 lux, and direct sunlight can exceed 100,000 lux. Your device's ambient light sensor measures the lux level of your current environment.
How does the ambient light sensor affect auto-brightness?
Your device uses the ambient light sensor to automatically adjust screen brightness based on surrounding light conditions. In bright environments, brightness increases for visibility. In dark rooms, it decreases to reduce eye strain and save battery. Testing the sensor confirms this feature works properly.
Time to upgrade? Consider these lighting:
Support Check A Device
If you find our free tools helpful, consider supporting us! Your contributions help us keep the site running and ad-free.