README

activity_reporter is responsible for reporting when the browser (or other embedder) is actively used to the browser's vendor. This enables the vendor to count the number of active users of the browser.

Historically, this data was reported only through the updater: the browser would signal the updater that it had been used, and when the updater next checked for updates, it would tell the update server whether or not the browser had been actively used. This report happens regardless of usage-stat opt-in, in a de-identified and privacy-preserving way.

activity_reporter re-implements that same function, but separate from the updater, to better isolate functionality. It may be disabled by the report_activity=false GN arg.

The update protocol documentation describes the transmitted information and deduplication algorithm in more detail.