Privacy Policy

The short version

If you sign in, we store your learning progress on our servers so it follows you between devices, and we use what you have read to suggest what to read next. Like any website, our servers keep technical logs.

Tsukigo does not run advertising or third-party analytics, and we do not sell personal data.

This summary is here to be read. The sections below are the full picture.

1. Who is responsible

Tsukigo is operated by Luminary LLC (N&E Bldg. 6F, 1-12-4 Ginza, Chuo-ku, Tokyo 104-0061, Japan), which is responsible for the personal data described here. For any question about your data, or to exercise any of the rights below, email us.

2. What we collect

Without an account. Your browser stores things on your own device: your display and reading preferences, the interface language, the level and language you are studying, a record of what you have read, and similar settings. Some of these are cookies and are therefore sent to our servers with each request. If you later create an account, your device may add what it has stored to that account so your progress is not lost.

If you create an account. The sign-in identity your chosen provider gives us — your email address and, depending on the provider, a display name and profile picture. Where a password is used, our identity provider stores it in hashed form and we never see it. Your browser stores a sign-in token, and our server sets a session cookie that keeps you signed in.

Your learning activity, if signed in. What you have read, words you have marked as known or saved, practice answers, your level and study-language settings, your preferences, and a record of which versions of these documents you have accepted. This is what makes progress tracking, your vocabulary list, and suggestions work.

Material you send us. Feedback, reports, and anything else you send, together with basic context about where in the app you were and what browser you used, so a report can be located without you having to describe it. Your account id is attached if you are signed in; anonymous submissions carry none.

Technical logs. Our servers record requests, including IP address, user-agent, the page requested, the time, an identifier for your browser and, if you are signed in, your account. We may also receive error reports from your browser. We use these to keep the Service running and secure and to improve it.

We may collect other data as the Service develops. Where we do, we will update this policy.

3. Why we use it, and on what basis

We use sign-in data to give you an account, and learning activity to provide the features you signed in for — in both cases to perform our agreement with you. We use technical logs and material you send us for security, debugging, support, and improving the Service, on the basis of our legitimate interest in running and protecting a working product.

We use what you have read to decide what to suggest to you next. This shapes what you see in the app; it produces no legal or similarly significant effect, and you are free to ignore any suggestion.

We do not use your personal data to make automated decisions about you that produce legal or similarly significant effects. We do not currently use it for advertising.

Where we rely on legitimate interests, you can object to that use of your data at any time — email us.

4. Cookies

We use cookies to make the Service work correctly and to improve it: for example, to keep you signed in, to remember your settings, and to recognise your browser when you return. The cookie that identifies your browser expires a year after your last visit.

5. Who else sees it

We use service providers to run Tsukigo and to produce its content. They act on our instructions and under contracts governing what they may do with your data. Our providers currently include:

Google Cloud, which hosts the Service, your account, and your saved progress.

Cloudflare, which delivers the Service and protects it from attacks.

Anthropic and Google Cloud AI, which are used to produce and maintain the content in our library. They may also process material you send us, such as feedback, when we are working through it.

If you choose to import your progress from another learning service, we connect to that service at your request and on your instruction — it is not one of our providers, and it acts for you, not for us. Today the only such service is WaniKani. You give us a read-only access token, we use it once to read your own progress, and we do not store the token: you will be asked for it again next time. We keep only our own record of which words you know, not any of that service's own teaching material. You can remove imported progress at any time in Settings.

We may also disclose data where the law requires it, where it is necessary to establish, exercise, or defend legal claims, where it is necessary to protect the Service or its users from abuse, or — if the Service is ever transferred to new ownership — to whoever takes it on.

We do not sell your personal data, and we do not currently share it for advertising purposes.

6. Where your data is stored

Our servers and databases are located in the United States. If you are in the European Economic Area, the United Kingdom, or Japan, this means your data is transferred outside your country.

For those transfers we rely on the safeguards our providers make available in their data-processing terms, which include the European Commission's standard contractual clauses and, where applicable, certification under the EU–US Data Privacy Framework. Those terms are published by the providers themselves; email us and we will point you to the current version.

Information about how our providers handle personal data in the countries where they operate, including the measures they take, is published in their own documentation.

7. How long we keep it

Account and learning data is kept until you delete your account.

Technical logs and browser error reports are kept for up to 90 days.

Material you send us, such as feedback, is kept for as long as it is useful for the purpose it was sent for — resolving the issue, understanding recurring problems, and keeping a record of what was decided. We delete it when it is no longer needed. If you delete your account, your account id is detached from it.

Aggregate counts that identify nobody, such as how many stories were read in a month, may be kept indefinitely.

8. Your rights

Depending on where you live you have some or all of the following rights: access to the personal data we hold about you; portability of that data in a machine-readable form; deletion of your account and your learning data ("How long we keep it" above explains the one thing that is kept, with your account id removed); correction of anything wrong; objection and restriction, to ask us to stop using your data for a particular purpose; and withdrawal of consent, where we relied on it.

You can delete your account and your learning data yourself, at any time, from your account page; Delete your account explains how, and what is kept. To exercise any other right, email us and we will respond within the time the applicable law allows. We may ask you to confirm your identity first, so that we do not disclose your data to someone else.

You also have the right to complain to your local data-protection authority.

9. Children

The Service is open to readers of any age. Creating an account requires you to be at least 13 years old, and where the law where you live sets a higher age for consenting to data processing, a parent or guardian must agree on your behalf.

We do not knowingly collect personal data from children below that age. If you believe an account has been created by someone below it, email us. We may suspend or remove any account.

10. Security

Your data is held on managed cloud infrastructure providing encryption in transit and at rest, and access is limited to those who need it. No service can guarantee security, and we do not.

11. Changes to this policy

We may update this policy as the Service develops. When we do, we revise the date above, and where a change materially affects you we will take reasonable steps to bring it to your attention.

12. Contact

Questions about your data, or want to exercise any right above? Email us.