In accordance with the requirements of the law that came into force (California Consumer Privacy Act) by Mozilla in the release of Firefox 72, scheduled for January 7, the ability to initiate the deletion from the Mozilla servers of data received during the collection of telemetry and to a specific browser instance.
The CCPA provides the right to know exactly what personal data is being collected and to whom it is being shared, requires access to that data, and the ability to modify, delete, and prohibit the sale of personal data that has already been collected. While the CCPA's privacy protections only apply to California residents, Mozilla has decided to provide telemetry deletion tools for all users, regardless of where they live.
Data is deleted in case of refusal to collect telemetry in the section "about:preferences#privacy" ("Firefox Data Collection and Use"). When you uncheck "Allow Firefox to send technical and interaction data to Mozilla", which controls the sending of telemetry, Mozilla within 30 days all data collected in the time before the failure of the telemetry transmission. The data collected on Mozilla's servers during telemetry collects information about performance, Firefox security, and general parameters such as the number of open tabs and session duration (information about the sites opened and search queries is not transmitted). Full details of the data collected can be viewed on the "about:telemetry" page.
Source: opennet.ru