Lightbeam, a download produced by Mozilla, the US free software community behind the popular Firefox browser, claims to be a “watershed” moment in the battle for web transparency.

Everyone who browses the Internet leaves a digital trail used by advertisers to discover what your interests are.

Users who activate Lightbeam will be able to see a real-time visualisation of every site they visit and every third-party that is active on those sites, including commercial organisations which might potentially be sharing your data.