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Backups on Android.
On Android your Kata data lives on your phone, and two things keep it safe: Android's own Google backup, and a sealed copy that only your key opens, which brings Kata to a new phone.
Your Google backup
Android backs your apps up to your Google account when backup is on in your phone's Settings, usually under Google or System, Backup. Kata's backup files ride along, and they hold your logs, chats, Kata's memory, photos and settings. The backup sits under your Google account and Google's terms, and Kata reads nothing of it.
Back up now in Settings, Data writes a fresh backup file, and the automatic frequency (daily, weekly, monthly or manual, weekly unless you choose another) runs when you open Kata. Android then carries the latest state with its next device backup, which it runs on its own schedule, usually about once a day while the phone charges on Wi-Fi.
Google's backup holds up to 25 MB per app. If Kata grows past that, mostly through photos, Android stops backing it up, so keep a copy with Export my data as well.
What it leaves out
The values Kata reads from Health Connect stay out of the Google backup. They live in Health Connect, and after a restore Kata reads them again from there, for the last 30 days. Everything you logged yourself is in the backup.
The sealed copy for a new phone
Kata also keeps one end-to-end encrypted copy of your account, the same kind the web app keeps. It is encrypted on your phone with AES-256-GCM before it leaves, under a random key Kata never receives, and stored as one sealed row we have no technical means to read. Your photos are never in it, and it is deleted with your account.
The key is kept for you in Google Block Store, Google's encrypted store for keys, tied to your Google account. Set up a new Android phone from your Google account, install Kata, sign in with the same account, and Kata opens the copy on its own. Block Store needs the phone to back up to your Google account, usually with a screen lock set. If it cannot, Settings, Data, Moving to a new device says the key is kept on this phone only: then save your recovery key.
Your recovery key
Under Settings, Data, Moving to a new device you can show the recovery key (52 letters and numbers), copy it, or show it as a QR code that another device's camera scans straight off the screen, never through a server. It is the way to any other kind of device: a browser, or a phone without your Google account. Keep a copy somewhere safe: if your phone, the key in your Google account and the recovery key are all gone, the sealed copy can never be opened again, by you or by us.
Moving to a new Android phone
- On the old phone, open Settings, Data, tap Back up now, then Export my data, and keep that file somewhere you control.
- Set up the new phone from your Google backup, so Kata's data and its key come across, then install Kata and sign in with the same account.
- If your data is not there, tap Restore with a recovery key under Moving to a new device, or Import the file you exported.
Moving directly from the old phone to the new one, by cable or over Wi-Fi, also works: Android carries Kata's backup files and its storage across without keeping them anywhere in between.
Coming from iPhone or the web
The iPhone and Android apps do not share a backup: on the iPhone, use Export my data, move the file to the Android phone and tap Import there. From the web, tap Restore with a recovery key under Moving to a new device on the phone, and enter the key from your browser or scan its QR code. See Changing your device.
Delete account deletes the sealed copy with the account, and asks whether the backup files on this phone go too. Kept files stay in Kata's folder and in your Google backup, so a new account on this phone can restore one. See Profile and account.