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    Check device online
    1. Home
    2. Sensors
    3. Ambient light

    Ambient Light Sensor Test

    Connecting to sensor…
    Current illuminance— luxWaiting for a reading
    Minimum
    — lux
    Maximum
    — lux
    Update rate
    —

    How to check the sensor

    1. Find the likely sensor location on your device using the guide below.
    2. Cover that area with your hand and watch the lux value decrease.
    3. Uncover the sensor and turn the device toward a window or lamp; the value should increase.

    Where is the ambient light sensor?

    The exact position depends on the model. Do not cover the whole device: move one finger around the marked areas and watch for a change in lux.

    Phone

    Usually at the top of the front panel near the earpiece or selfie camera. On newer models it can be hidden under the display; some phones also use a rear light sensor near the cameras.

    Tablet

    Usually in the bezel near the front camera. Its side changes with the camera position; some tablets also have a rear sensor beside the camera.

    Laptop

    Usually in the upper display bezel close to the webcam. It may look like a tiny dark window or be hidden inside the bezel.

    What does an ambient light sensor measure?

    An ambient light sensor measures illuminance around a device in lux (lx). Phones, tablets and laptops use this information mainly to adjust screen brightness. This test reads the same sensor through the browser when the Ambient Light Sensor API and the device driver make it available.

    How to test the light sensor

    1. Wait for a current lux value. If automatic access fails, press “Start test”.
    2. Find the sensor near the front camera or display bezel. Cover one small area at a time until the reading decreases.
    3. Uncover it and turn the device toward a window or lamp. The reading should increase. There is no pass or fail score because sensors, drivers and browsers report light differently.

    The panel also shows the minimum, maximum, average, range and effective update rate collected during the current visit. Values are processed locally and are not saved.

    Browser support and the Chromium flag

    The Ambient Light Sensor API is experimental and requires a secure page. In Chrome, open chrome://flags/#enable-generic-sensor-extra-classes; in Edge, open edge://flags/#enable-generic-sensor-extra-classes. Set Generic Sensor Extra Classes to Enabled and restart the browser. Firefox and Safari have no equivalent flag. Even after enabling it, the operating system may keep the physical sensor unavailable to websites.

    How to interpret lux values

    The text label is only an approximate description: less than 1 lx is almost dark, up to 50 lx is very dim, 50–300 lx is dim indoor light, 300–1,000 lx is bright indoor light, and values above 10,000 lx normally indicate daylight. Different devices may round readings or report different values in the same place, so watch the direction and size of the change rather than comparing two devices as calibrated light meters.

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