Privacy Policy

This policy explains what information Zettel collects, why, who processes it for us, how long we keep it, and the choices and rights you have. Zettel is operated by [legal entity name], [registered address], which is the controller of your personal data. Contact us at legal@zettel.study.

The short version:

We use your lessons to teach you. We do not sell your data and we do not show ads.
AI providers process your messages and speech to run the Teacher. Under their API terms, they do not use it to train their models.
We do not store recordings of your voice. We keep a text transcript of what you say in a lesson.
Your lessons are private. A replay becomes public only if you publish it, and it never includes a recording of your voice or a transcript of what you said.
Analytics cookies are off in the EEA, the UK and Switzerland unless you accept them.
You can download your data and delete your account.

1. Information we collect

Account. Your email address, name, username, and the profile details you add. If you sign in with Google or GitHub, we receive your account identifier, email, and name from them. Passwords are stored only as salted hashes by our authentication provider.
Lessons. Your learning goals and journey maps; the messages you type; transcripts of what you say; the Teacher’s words and voice; the worlds built for you; and your work inside them, such as answers, predictions, drawings, marks, and code.
Learning observations. Notes the Teacher records about your learning, such as what you have shown you understand or where you struggled. They are used to continue your lessons where you left off.
Files and links. Documents, images, and links you add to a lesson (up to 50 MB each), and the text we extract from them.
Support. The messages and attachments you send us, plus technical details that help us fix the problem, such as the page you were on, your browser, and your IP address.
Payments. Your plan, subscription status, lesson-time balance, and a Stripe customer identifier. Stripe collects your card details; we never receive or store full card numbers.
Device and usage. IP address, browser and device type, pages visited, performance timings, and error traces. If analytics is on (see section 4), product usage events.
Email. Delivery status of the emails we send you, such as whether a message bounced.

2. Voice and transcripts

Voice is optional. When you talk to the Teacher, your browser streams your microphone audio directly to our voice provider, OpenAI. Its voice model listens and speaks with you, and passes what you say to the Teacher. The microphone is on only while voice is on.
We do not store recordings of your voice. If we ever offer to keep them, it will be off unless you turn it on.
We keep a text transcript of what you say, as part of your lesson. We also keep the Teacher’s voice audio and its words, so that you can replay your lesson.
Your transcripts are private to your account, and they are never part of a public replay.

3. How we use information, and our legal bases

To teach you and run your account (performance of our contract with you): running lessons, building worlds, continuing where you left off, keeping your lesson history, and processing payments.
To keep the Service secure and working (our legitimate interests): preventing abuse and fraud, enforcing lesson-time limits, diagnosing errors, and measuring performance.
To improve the Service (legitimate interests, or your consent where the law requires it): understanding how features are used through analytics.
To communicate with you (contract, or consent for optional updates): sign-in emails, receipts, service notices, and product news you can unsubscribe from.
To meet legal duties (legal obligation): tax and accounting records, and responses to lawful requests.

We do not make decisions about you that have legal or similarly significant effects based only on automated processing. The Teacher adapts what it teaches to you; that is the Service you ask for.

4. Cookies and analytics

Necessary storage. Your browser stores your sign-in session and interface preferences, such as theme and panel layout. Cloudflare, which delivers the site, may set security cookies to block bots, and Cloudflare Turnstile checks that sign-up and sign-in come from a person. The site does not work without these, so they are always on.
Analytics. We use PostHog to understand how people use Zettel. PostHog sets cookies and browser storage to recognise a returning browser. In the EEA, the UK, and Switzerland, analytics stays off until you accept it in the cookie banner. Elsewhere it is on by default. Anyone can change the choice at any time with Cookie settings in the site footer. Analytics events are never sent from public replay pages.
Embedded videos. Videos in blog posts and lessons load from YouTube’s privacy-enhanced domain, youtube-nocookie.com. YouTube does not store information about you until you play a video.
Performance traces. The site sends timing and error information about its own requests to our monitoring provider. This uses no cookies.

5. AI processing

To teach you, we send your lesson content to AI model providers: your messages and transcripts, relevant earlier lessons and learning observations, and the text of files you add. They return the Teacher’s replies and the worlds on the stage.

Anthropic runs the Teacher and builds worlds. OpenAI runs the voice, the planning of your journey, and parts of lesson and support handling. Mistral AI reads text from scanned documents and images you add.
These providers process the data for us under their commercial API terms. Under those terms they do not use it to train their models. They may keep it for a limited time, typically up to 30 days, to detect abuse, unless a shorter period applies.
When the Teacher looks for a picture, or you add a link, our servers fetch it from public sites such as Wikimedia Commons or YouTube. Those sites see a request from our servers, not your identity.

6. Who we share information with

We share personal data only with service providers that process it for us under contract, and only as needed for the purposes in section 3:

Supabase: database, sign-in, and file storage.
Vercel: application hosting.
Upstash: short-lived caching, rate limits, and live lesson events.
Convex: live delivery of lesson state to your browser.
Temporal: scheduling of background work, such as building a world.
Anthropic, OpenAI, and Mistral AI: AI processing (section 5).
Stripe: payments and tax.
Resend: sending email.
PostHog: product analytics, when on (section 4).
Pydantic (Logfire): error and performance monitoring.
Cloudflare: network delivery, protection, and bot checks.
Proton: our email inbox, when you write to us.

We may also disclose information when the law requires it, to protect the rights and safety of people or the Service, or as part of a merger or sale of the business, in which case this policy continues to apply to your data. We never sell personal data, and we do not share it for targeted advertising.

7. Public replays

Lessons are private. You can choose to publish a replay of a lesson; anyone with its link can then watch it.
A published replay contains the Teacher’s words and voice, pictures of the stage, and markers showing when you asked, answered, or practised. It does not contain recordings of your voice or a transcript of what you said or typed. The Teacher’s words can repeat things you said, and the stage can show your work, so watch the replay before you publish it.
Public replay pages are not indexed by search engines. You can unpublish at any time; deleting the lesson or your account withdraws the link too.

8. How long we keep information

Your account and lessons: while your account is open.
After you delete your account: we delete or anonymise your personal data within 30 days. Copies in our backups expire within [backup retention] after that.
Billing records: as long as tax and accounting law requires, typically [billing record period].
Journeys started without signing in: the conversation is deleted after 24 hours unless you sign up and keep the journey. The journey map drawn from it is kept, not linked to any account.
Error and performance logs: up to [log retention].
AI providers: see section 5.

9. Your rights and choices

Download your data. You can download a copy of your account and lesson data from your account settings.
Delete your account. You can ask for your account to be deleted from your account settings, or by email.
Other rights. Depending on where you live, you may have the right to access, correct, restrict, or object to our use of your data, to withdraw consent, and to data portability. California residents have the right to know, delete, and correct personal information, and not to be discriminated against for using these rights. We do not sell or share personal information as California law defines those terms.
To use any right, write to legal@zettel.study. We may need to confirm your identity. We answer within one month.
You can complain to your data protection authority. We would like the chance to help first, so please contact us.

10. Security

We encrypt data in transit with TLS, and our database and file storage providers encrypt it at rest. Files are kept in private storage. Access to your data is limited to your account by the application and, for staff, to the people who need it to run the Service. No system is perfectly secure; if a breach affects your personal data, we will tell you and the authorities as the law requires.

11. International transfers

Our database and file storage are in the United States, and several of our providers process data there. When we transfer personal data out of the EEA, the UK, or Switzerland, we rely on the European Commission’s Standard Contractual Clauses, the UK addendum, or the provider’s certification under the EU-US Data Privacy Framework.

12. Children

Zettel is for people aged 18 and over. We do not knowingly collect personal data from anyone under 18. If you think a person under 18 has given us personal data, write to legal@zettel.study and we will delete it.

13. Changes to this policy

We will post updates on this page with a new effective date. For a material change, we will tell you by email or in the Service at least 30 days before it takes effect.

14. Contact

Questions or requests about privacy: legal@zettel.study.