Live Lux Readings
Reads the AmbientLightSensor API where available to display the current illuminance in lux, updated in real time as the light around you changes.
Ambient Light Sensor Test
Live Lux Readings & Auto-Brightness
View live lux readings from your phone's ambient light sensor and test auto-brightness by covering and uncovering the sensor. The same sensor that adjusts your screen brightness automatically.
Sensor inactive
Current Light Level
—
lux
Awaiting sensor
Cover the top of your phone to see the reading change
Environmental Light Scale
0
100
1k
10k
100k+
Auto-Brightness Behavior
Idle
Screen Preview
Sim. Brightness
—
Start the test and cover/uncover the sensor to see the response
Lux History
No data
Features
What This Light Sensor Test Does
A simple, interactive check for your phone's ambient light sensor and auto-brightness.
Cover / Uncover Test
Cover the top of your phone with your hand — the lux reading should drop sharply. Remove it and it should rise again, confirming the sensor responds.
Lux History Graph
A rolling 120-sample graph plots your lux readings over time, so you can see how the sensor responds to changes in lighting instantly.
Auto-Brightness Preview
A simulated screen dims and brightens in response to the lux reading, illustrating how auto-brightness would adjust your display in real use.
Environment Classification
Automatically classifies the current reading — dark room, indoor, overcast, bright day — so you can quickly interpret your lux value.
100% Private
Everything runs locally in your browser. No data is transmitted, stored, or shared — just a simple, private light sensor check.
How It Works
Test Your Light Sensor in 4 Steps
No app, no sign-up — just a simple, accurate check.
Enable Sensor
Tap "Start Light Test" and allow the browser prompt to access the ambient light sensor.
Read Live Lux
The current light level appears in lux, with an environment label like "Indoor" or "Bright day".
Cover the Sensor
Place your hand over the top of your phone. The lux value should drop sharply and the simulated screen should dim.
Uncover & Confirm
Remove your hand — the reading should rise again, confirming the sensor and auto-brightness response work.
FAQ
Ambient Light Sensor Test — Common Questions
Everything you need to know about testing your phone's light sensor.
Open this page on your phone, tap "Start Light Test", and allow sensor access. The live lux reading shows the current light level. Cover the top of your phone with your hand — the lux value should drop sharply. Remove your hand and it should rise again. This confirms whether your ambient light sensor is working.
Typical lux values vary by environment: a dim room is around 10–50 lux, a normal indoor room is 100–300 lux, an office or bright indoor space is 300–500 lux, an overcast day outdoors is 1,000–10,000 lux, and direct sunlight can exceed 100,000 lux. Covering the sensor with your hand should bring the reading close to 0 lux.
The AmbientLightSensor API is currently supported only on Chrome for Android and a few other Chromium-based mobile browsers. Safari on iOS and most desktop browsers do not expose ambient light sensor data to web apps. If your browser doesn't support it, the test will show as unsupported — but the auto-brightness behavior can still be observed with the visual meter.
Common causes include a dirty or obstructed ambient light sensor (often near the earpiece), a screen protector covering the sensor, a software glitch, or auto-brightness being disabled in settings. Try cleaning the top of the screen, removing any case or protector near the sensor, toggling auto-brightness off and on in settings, and restarting the device. If the lux reading here doesn't change when you cover the sensor, the hardware may need repair.