I think that one of the most interesting things with all WebAPIs we’re working on, is to interact directly with the hardware through JavaScript, but also, as an extension to that, with the environment around us. Enter Ambient Light Events.

The idea with an API for ambient light is to be able to detect the light level around the device – especially since there’s a vast difference between being outside in sunlight and sitting in a dim living room – and adapt the user experience based on that.

One use case could be to change the CSS file/values for the page, offering a nicer reading experience under low light conditions, reducing the strong white of a background, and then something with more/better contrast for bright ambient light. Another could be to play certain music depending on the light available.

Accessing device light

Working with ambient light is quite simple. What you need to do is apply a listener for a devicelight event, and then read out the brightness value.

It comes returned in the lux unity. The lux value ranges between low and high values, but a good point of reference is that dim values are under 30 lux, whereas really bright ones are 10,000 and over.

window.addEventListener("devicelight", function (event) {
    // Read out the lux value
    var lux = event.value;
    console.log(lux);

});

Web browser support

Ambient Light Events are currently supported in Firefox on Android, meaning both mobile phones and tablets, and it’s also supported in Firefox OS. On Android devices (the ones I’ve tested), the sensor is located just right to the camera facing the user.

It is also a W3C Working Draft, following the type of other similar events, such as devicemotion, so we hope to see more implementations of this soon!

Demo

Dmitry Dragilev and Tim Wright recently wrote a blog post about the Ambient Light API, with this nice demo video:

You can also access the demo example directly, and if you test in low light conditions, you’ll get a little music. Remember to try it out on a supported device/web browser.