Luna Private

Luna Private — a period & cycle tracker whose data physically cannot leave your device.

Cycle tracking data is among the most sensitive categories a phone holds, and that stopped being a theoretical concern in the United States after 2022, when the legal exposure of that data became a live question. Several widely used trackers store it on servers, where it is subject to subpoena.

Data that physically cannot leave the device is the only design that answers this properly, because a promise not to share is a policy and policies change with ownership. The prediction side is worth understanding too: cycle length varies naturally between people and month to month, so a forecast is a range rather than a date.