KANTETSU Privacy policy

What Kantetsu stores, and what it does not.

Last updated 5 August 2026

Kantetsu is a personal rule-keeping app published by Systems Atlas Project. It needs an account, and the account exists for one purpose: so your rules and your history follow you to a new device instead of being trapped on an old one. Beyond that, nothing you write leaves your device unless you choose to sync it — there is no analytics, no crash reporting, no advertising and no tracking of any kind in this app.

Signing out deletes the data on your device. The app offers to upload it first and tells you plainly before it does anything; signing back in brings it down again.

What we collect

Your email address. Used to identify your account, to sign you in, and to send you a password-reset code if you ask for one. Your password is never stored — the server keeps only a bcrypt hash of it, which cannot be turned back into your password.

What you write in the app, when you sync it. That means your rules and their descriptions, your "what's driving you" statement, your day notes, the schedule you set for each rule, and the record of which days you marked kept or broken.

Syncing happens in the open, never in the background. Signing in downloads your account's data onto the device; beyond that, nothing moves unless you press Upload or Download, and the app tells you which direction it is about to go before it does anything.

What we do not collect

No location. No contacts, calendar, photos or files. No health or fitness data — Kantetsu records what you tell it about your own rules and reads no sensor. No advertising identifier. No device identifier of any kind. No analytics, no crash reports, no usage statistics, and no third-party tracking software.

On Android, Kantetsu requests exactly one permission: internet access, used only when you sign in or sync.

Who else sees it

Resend, and only for one thing: if you ask for a password reset, the server sends your reset code to your email address through Resend, an email delivery service. Nothing else is ever sent to them, and nothing is sent to them at all unless you request a reset.

Railway hosts the server and its database, and so stores the data described above on our behalf. They do not use it for their own purposes.

There is no one else. Your data is never sold, never used for advertising, and never shared with anyone else for any purpose.

Where it is kept, and for how long

On your device, and — once you sync — in a Postgres database hosted by Railway. It is kept until you delete it. Everything sent between the app and the server travels over an encrypted HTTPS connection.

Deleting your data

You can delete your account and everything in it from inside the app: Settings → Delete account. This is immediate and cannot be undone. It removes your email address, your password hash, your rules, every day you logged, your notes and your schedules from the server — and it also erases them from the device you are holding.

Signing out is different, and it is not nothing: it deletes the data on this device, while leaving your account and everything in it untouched in the cloud. The app offers to upload this device's data first, and tells you before it does anything. Sign back in and it comes down again.

Full instructions, including how to ask us to do it for you, are on the account deletion page.

Two things survive a deletion, and we would rather say so than not. If you have ever been sent a password-reset email, that email is in your own inbox and in Resend's delivery logs; the code in it expires an hour after it is sent. And our hosting provider keeps ordinary connection logs, which record that a request happened but not what you wrote.

This website

This site sets no cookies and runs no analytics. It is served by Cloudflare, which processes standard request information such as IP address in order to deliver the page and protect against abuse.

Your rights

You have the right to access the data held about you, request correction of anything inaccurate, request deletion, and export your data. To exercise any of these, email us or get in touch through the support page.

Children

Kantetsu is not directed at children and we do not knowingly collect data from anyone under 13.

Changes

If this policy changes, the date at the top changes with it, and the previous version is replaced here.

Contact

Questions about this policy, or about your data: kantetsu@systemsatlasproject.com.