KoezuKoezu Privacy Policy
Effective 12 November 2026
Koezu is provided by its sole-proprietor operator in Kyoto, Japan ("we"), independently of Kyoto University of Advanced Science and the NISAR Laboratory. For anything in this policy, write to support@koezu.com. We give our postal address without delay on request.
In short: decks you don't share stay on your device. Decks you share are encrypted in your browser with a key we never have, so we can't read them. We don't sell personal information, show ads or use tracking cookies.
What we keep, why, and for how long
| What | Why | How long |
|---|---|---|
| Account: your name and email address; the public keys of your passkeys; and, if you link one, the account ID and email of your Google or Microsoft account. Your fingerprint, face and PIN never leave your device. | To sign you in and contact you about your account | Until you delete your account |
| Sign-in: a hashed session token and your browser type; one-time email codes, stored only as a hash | To keep you signed in safely | Sessions: up to 30 days of inactivity. Codes: 10 minutes |
| Agreement records: the version of the terms you agreed to, when, your browser and your country | To show what you agreed to | As long as the law requires, including after your account is deleted |
| Plan and billing: your plan and its dates, your country, and Stripe's customer and payment references. For invoices: the name, institution and billing details you give us. Card details go to Stripe and never reach us. | To provide your plan and keep the accounting records the law requires | Accounting records: as long as Japanese tax law requires (up to 7 years) |
| Requests and invitations: what you asked for in a free-access request, your institution and reason, any school address your Google or Microsoft sign-in verified, and who invited you | To review requests and run invitations | While your account exists |
| Metered use: how many Koezu AI credits, premium-voice minutes and translations you used | To apply your plan's allowances | While your account exists |
| Shared decks: their media, comments and the names commenters type, all encrypted in the browser | To deliver the deck to the people you share it with | Until the owner deletes it, or after 365 days unopened |
| Link email checks: the email address a viewer enters to open a link that asks for one, and the one-time code, stored only as a hash | To let only people with a confirmed email open that link, and to show the deck's owner which address opened it | Codes: 10 minutes. Addresses: until the owner makes new links or the shared deck is deleted |
| Server records: internet address, time and request, kept by our host | To run and protect the service | A short period set by our host |
Anonymous usage counts. The app counts how many times a day a few things happen: a first import, a live block, a narration, a share or export, a plan prompt shown or acted on, a purchase, and a visit from the "Made with Koezu" badge. Only daily totals are kept, with no account, internet address or device. Counts are sent only while you are signed in or using the web app, never from a shared deck's link. You can turn them off under File › Your plan › "Send anonymous usage counts".
Cookies and storage. We use one cookie to keep you signed in. A visit from the "Made with Koezu" badge sets one more cookie, saying only "came from the badge", so a sign-up within 30 days can be counted. Your decks, settings and plan token are kept in your browser or app, on your device.
AI and voice features
- With your own key, your content goes from your device straight to the AI or voice provider you choose, under that provider's terms. It doesn't pass through us.
- Koezu AI sends your request through our server to Anthropic, and the answer comes back the same way.
- Koezu translation sends the text to be translated through our server to Microsoft (Azure AI Translator), and the translation comes back the same way.
- Koezu premium voice sends the narration text through our server to Microsoft (Azure AI Speech) or, for the Google voices, to Google (Cloud Text-to-Speech), which returns the audio.
- For all three, we don't store or log what is sent or returned, only usage counts. These providers work for us under business terms that don't allow them to train their models on it.
- Recordings of your voice, camera and ink stay on your device, unless you share the deck. They are then encrypted like the rest of it.
Who processes data for us, and where
| Provider | What for | Where |
|---|---|---|
| Cloudflare, Inc. | Hosting and storage | A US company. Data is stored in the Asia-Pacific region, mostly in Japan; this is not guaranteed |
| Stripe (Stripe Japan K.K. and Stripe, Inc.) | Payments for purchases in Japan | Japan and the United States |
| Sold through Link, LLC (Stripe) | Seller of purchases made from outside Japan, under its own privacy policy | United States |
| Resend (Plus Five Five, Inc.) | Sign-in and account emails | A US company, sending from its Tokyo region |
| Anthropic, PBC | Koezu AI | United States |
| Microsoft Corporation | Koezu translation and premium voice; Microsoft sign-in, if you choose it | United States |
| Google LLC | Premium voice, if you choose one of its voices; Google sign-in, if you choose it | United States |
Some of these providers are outside Japan, or may process data in the United States, whose rules on personal information differ from Japan's. Japan's Personal Information Protection Commission summarises the US rules at https://www.ppc.go.jp/enforcement/infoprovision/laws/offshore_report_america/. Each provider is bound by contract to protect the data it handles for us. On request, we will tell you more about the measures they take.
How we protect it
- Shared decks are end-to-end encrypted.
- Passkeys are used for sign-in, and session tokens and codes are stored only as hashes.
- Every connection is encrypted.
- Only the operator can access account data.
- Hosting and processors are chosen for their security controls.
We will give more detail on request.
Your requests
You may ask us to tell you what we hold about you, or to correct, add to or delete it. You may also ask us to stop using it or to stop sharing it. Write to support@koezu.com from the address on your account. There is no fee. We answer without delay, after confirming it's you. Deleting your account removes your account, passkeys, linked accounts and sessions. Agreement and accounting records are kept as stated above. Complaints go to the same address.
If you are in the EEA or the UK:
- We use account and billing data to provide the service you signed up for.
- We keep records because the law requires them.
- We keep server records to protect the service.
- You can also complain to your local data protection authority.
Children
Koezu is not meant for children under 13, and we don't knowingly collect their personal information.
Changes
We post changes here with their effective date. We tell you about important changes in the app or by email before they take effect.