The short version: FastLumi stores only what it needs to run your timer and, if you choose an account, sync your fasts.
Without an account, your fasts, weights, and settings stay in this browser or app on your device.
With an account, we store your email address and the FastLumi data you sync: your fasts, weights, and settings. Accounts exist so your fasts can sync and be backed up across devices.
Your password is stored only as a salted cryptographic hash. It cannot be read back by FastLumi.
If you send feedback, FastLumi stores your message, rating, and category so the maker can read it and improve the app. If you are signed in, the feedback is attached to your account; if not, it is stored with the email address you choose to include, or anonymously.
Community is off unless you turn it on in your account settings. If you join, other community members can see your display name, the fasts you choose to share, your text posts, cheers, and comments, and your position on weekly leaderboards (fasts completed, streak days, and goal hours). Your weight is never shared. Turning community off hides your shared posts again.
You can export your data from History at any time. Deleting your account erases your account and its synced data. A copy kept only on a device remains there until you use “Erase everything” on that device.