Privacy policy

Daihon is a free, non-commercial trainer for spoken Japanese run by an individual developer. This page explains what data the site keeps, why, and how to get rid of it. Last updated: 3 October 2026.

What is collected

• Account. Email address, an optional display name and a hash of your password (the password itself is never stored).
• Sign-in with Google. Only your Google account identifier, email address and name — the openid, email and profile scopes. Nothing else from your Google account is requested or stored.
• Practice. Your attempts at dialogues and the final recognised text of each spoken line. Speech recognition is done by your browser's Web Speech API; the site never receives or stores audio recordings.
• Security. IP address and browser user agent for active sessions and in an activity log used to detect abuse. For guests only a salted hash of the IP address is kept.

Cookies

Only functional cookies: sign-in session, guest identifier, theme, language and sound settings. There are no advertising or tracking cookies. Traffic statistics come from Vercel Web Analytics, which does not use cookies.

Who processes the data

The data is not sold or shared for advertising. It is stored and processed by the services the site runs on: Vercel (hosting), Neon (database), Cloudflare (Turnstile bot check, storage of dialogue audio and forwarding of mail sent to the support address), Resend (account emails) and Google (sign-in, if you choose it).

How long it is kept

• The activity log is deleted after 7 days.
• Guest data without any practice is deleted after 90 days.
• You can delete your account yourself on the dashboard. Sign-in is closed immediately, and after 30 days the account is anonymised and the email address released.

Your rights and contact

You can ask what data is held about you, ask for it to be corrected or deleted, or ask any other question about privacy by writing to support@daihon.app.