With Mozilla’s Telemetry system, we have a powerful way to collect measurements in the clients while still complying to our rules of lean data collection and anonymization. Most of the measurements are collected in form of histograms that are created on the client side and submitted to our Telemetry pipeline. However, recent needs for better … ->

https://www.a2p.it/wordpress/tech-stuff/mozilla/measuring-tab-and-window-usage-in-firefox/