How is retention measured, and what criteria are used for time spent? Is it sufficient for a tab to be open, or does the blog need to be actively read?
Tracking starts as soon as our Liveblog script is loaded. The current time spent is reported to our backend at regular intervals. The statistics display the average, meaning we sum up all the data and divide it by the number of unique users.
This feature only works correctly if unique user tracking is active for as many users as possible (via the useCookiesoption).
From a technical perspective, we use the browser's visibilitychange and pagehide/pageshow events, as well as an internal watchdog timer, to determine whether the page was actually visible during that time.