chrono-surf by exstart

This extension essentially has two features:
1. The ability to measure the duration of a browsing session: to do this, as soon as the browser opens, the user can click on the toolbar icon at any time; a real-time stopwatch will appear.

Bonus: at one-hour intervals, the user is notified and regularly reminded to take a break.

1. Recording the cumulative time spent on each website: with each visit, the calculated time is added to the time already saved; thus, an estimate can be obtained for an hour, a day, a week, or even longer. This can be viewed via the show statistics button.