Your Phone’s Battery Status Is Being Used To Track You Online

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A new tracking method has been found to track you using your mobile phone battery – and you can’t turn it off.

A web standard that lets site owners tell how much battery life a mobile device has left has been found to enable tracking online – just a year after privacy researchers warned that it had the potential to do just that, the Guardian reports.

The battery status API was introduced in HTML5, the fifth version of the code used to lay out the majority of the web, and had already shipped in Firefox, Opera and Chrome by August 2015.


Basically, it allows site owners to see the percentage of battery life left in a device, as well as the exact seconds it will take to discharge or the time it will take to charge if connected to a power source.

It was originally intended to allow site owners to serve low-power versions of sites and apps to users with low battery power, but privacy researchers soon pointed out that it could be used to spy on users.

Now, two security researchers from Princeton University have shown that the battery status indicator really is being used to track mobile phone users.

By running a specially modified browser, Steve Engelhard and Arvind Narayanan found two tracking scripts that used the API to ‘fingerprint’ a specific device, allowing them to continuously identify the user while they online – even if the user was on a few different browsers at one time, including private ones.

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While the API is only being used by tracking scripts right now, Lukasz Olejnik, who highlighted the research, warns that it could be abused.

He said: “Some companies may be analysing the possibility of monetising the access to battery levels. When battery is running low, people might be prone to some – otherwise different – decisions. In such circumstances, users will agree to pay more for a service.”

Basically, your low battery power could signal website owners that your phone is going to die soon, and in return, you may just pay more for products or services.

Moral of the story? Keep your battery fully charged when buying online – it may save you a bit of money.