Privacy Policy

Last updated: 10/10/2026

The short version

• We only collect what we need to be your tutor: your sign-in info, the textbooks and syllabi you upload, your chats, and the skill map the app builds from them.
• Your chats and the pages of your uploads are sent to three AI providers — Google, xAI, and Anthropic (section 5) — to generate the tutor's replies and read your materials. That is the same on the free chapter and on every pass.
• We don't sell your data. We don't run advertising. We don't train models on it.
• You can delete your account and everything with it; only de-identified cost records remain (section 7). We're 18+ only.

1. Who we are

Professor Otto is an independently operated service, run by its owner as an independent sole proprietor. We are the controller of the personal data described here. To reach us about privacy — or anything else — email support@professor.ac; that inbox is the way to contact the operator.

2. What this policy covers

This policy applies to the Professor Otto web app and the data that flows through it. It does not cover what Google, xAI, Anthropic, or any other third party does with your data once they receive it — that falls under their own privacy policies.

3. What we collect and store

Account info

• A Clerk-managed user ID (our authentication provider)
• Your email address (optional, stored only if you provide one)
• Account creation and last-activity timestamps

We never see or store your password. Clerk handles sign-in.

Your uploaded materials

• Textbook PDFs you upload
• Supplemental files you attach to a book (problem sets, notes, etc.)

Files are stored in object storage (Cloudflare R2 in production, local disk in development), organized by your user ID. Each file is served from a long, random, unlisted address: the app only ever shows your files to you, and we never publish or share those addresses, but anyone who obtained a file's exact address could open it.

Data we derive from your materials

• Extracted text and chapter structure (so the tutor can reason about what's on page 47)
• An index of the definitions, theorems, examples, and exercises in your materials (so the tutor can find and cite them)
• Your skill map, learner profile, observations, and aptitude signals (so the tutor learns how you learn)

Your study sessions

• Full chat transcripts between you and the AI tutor
• Session metadata (what chapter, what mode, progress indices)
• Silent behavioral signals the AI uses to adapt — e.g., "asked for a hint," "solved without help"

Usage and technical records

• A record of each AI call made for you: which provider and model, token counts, cost, timing, and whether it succeeded or failed (this is how we measure your pass's fair-use allowance and the free chapter's limit)
• A record of errors you ran into, such as a tutor reply that failed or a session that couldn't start, so we can find and fix problems
• Error reports (Sentry), which include your account ID and the request that failed, but not your name, email, or chat content
• Standard server logs (timestamps, request paths, status codes)

What we don't collect

• Analytics SDKs — none (no PostHog, Amplitude, Google Analytics, Mixpanel, etc.)
• Advertising cookies or trackers — none
• Location beyond what's implicit in an IP address — none

4. How we use what we collect

• Your materials and derived data are used exclusively to run Professor Otto for you: indexing, search, chat context, and your skill map.
• Your chat transcripts are stored so you can return to a session; they also update your learner profile so the tutor adapts to you.
• We do not sell data, run advertising, train third-party models on your data, or use your uploads for anyone else's benefit.

5. Who processes your data on our behalf

These services receive some of your data so the product can function:

AI providers. These receive your chat messages, recent history, excerpts and page images from your uploaded materials, and a summary of your learner profile, to generate the tutor's replies and to read and organize your materials. The same three serve every account, on the free chapter and on every pass:

• Google (Gemini) — teaches your lectures, reads the pages of your uploads, and does most of the lighter work of organizing them.
• xAI (Grok) — does the heavier reasoning behind the scenes: outlining each unit, finding the practice problems in your materials, building your flashcards and skill map, and studying how your course grades.
• Anthropic (Claude) — writes the worked answers your practice is checked against.

Which of them handles a given request depends on the task and on availability: if one provider is temporarily out of capacity, the request may go to another of the three.

Service providers.

• Clerk — handles sign-in and session management. Sees your email and sign-in events.
• Lemon Squeezy — our reseller and merchant of record for passes. When you buy a pass, they process the payment and handle billing, receipts and invoices, refunds, and applicable tax. They receive the payment and billing details you enter at checkout (we never see or store your full card number). Governed by their own privacy policy.
• Fly.io — runs our servers, which process all of the data described in section 3.
• Neon — hosts our database.
• Upstash — runs the queue our background jobs use, which carries account and file identifiers.
• Cloudflare — stores and serves your uploaded files (R2) and provides our domain's DNS.
• Vercel — hosts the web app you use in your browser.
• Sentry — receives error reports, with your account ID, so we can debug failures.
• Telegram — delivers operational alerts to the operator. These contain internal account and file identifiers only, never your name, email, or content.

We do not share your data with anyone outside these lists for any other purpose.

6. What actually goes where

We provide the AI compute for every account; you never need an account or key with an AI provider. When you chat:

1. We assemble a prompt from your message, recent chat history, retrieved excerpts from your textbook, and a summary of your learner profile.
2. We send that prompt, using our platform credentials, to one of the AI providers listed in section 5.
3. The provider returns a response. We store it in your session history and show it to you.

Reading your uploads works the same way: page images go to Google to be transcribed, and pages and their text go to the providers in section 5 to be organized into your course and its practice.

7. How long we keep it

By default, we keep your data as long as your account exists:

• Uploaded files, derived text and indexes, skill map, learner profile, and chat transcripts — retained until you delete them or close your account.
• Usage and error records (section 3) — retained for cost accounting and to keep the service reliable.

When you delete a book, its files, text, indexes, and related learner data are removed from our database and object storage. When you delete your account, the same applies to everything tied to it, with one exception: usage and error records are kept for cost accounting, but the link to your account is removed, so they no longer identify you.

If you want us to accelerate any of that, email us.

8. Security

• In transit: HTTPS/TLS for all traffic between your browser, our servers, and third parties.
• Access: only you can read your own books, chats, and learner data; requests are authorized against your Clerk user ID on every call.
• We are a small team and don't claim perfect security. If you suspect a vulnerability, email support@professor.ac and we will respond quickly.

9. Your data protection rights

We handle your data in line with applicable data protection law. You have the right to:

• Access the data we hold about you
• Correct it if it's wrong
• Delete your account and associated data
• Complain to your local data protection authority if you think we've handled your data improperly

To exercise any of these rights, email support@professor.ac.

10. Your rights under the GDPR (EU/EEA, UK, and Swiss users)

If you use Professor Otto from the European Economic Area, the United Kingdom, or Switzerland, the GDPR (and UK GDPR) applies to our processing of your personal data. The operator described in Section 1 is the data controller.

Legal bases for processing. We rely on:

• Performance of a contract — to provide the tutor you signed up for: your account, uploaded materials, study sessions, and skill map.
• Legitimate interests — to keep the service secure, debug errors, and prevent abuse, balanced against your rights and freedoms.
• Consent — for anything optional you choose to enable; you can withdraw it at any time without affecting processing already carried out.
• Legal obligation — where we must retain records, such as tax and accounting records tied to payments.

Your rights. In addition to the rights in Section 9, you can: access your data; have it rectified or erased; restrict or object to its processing; receive it in a portable, machine-readable format; and withdraw any consent you gave. To exercise any of these, email support@professor.ac. We aim to respond within one month.

International transfers. We and some of the processors listed in Section 5 (for example, the AI providers, Clerk, Cloudflare, and Lemon Squeezy) are located outside the EEA. Where personal data is transferred outside the EEA, it is protected by an appropriate safeguard — such as a European Commission adequacy decision for the country where it is processed, the EU Standard Contractual Clauses, or the EU–US Data Privacy Framework where applicable.

Automated decision-making. Professor Otto personalizes your learning — your skill map and learner profile adapt to how you study — but we do not make automated decisions that produce legal or similarly significant effects about you.

Complaints. You have the right to lodge a complaint with your local data protection authority in the EEA, the UK, or Switzerland.

11. Your rights under US state privacy laws (California and similar states)

If you use Professor Otto from California — or another US state with a comprehensive consumer privacy law — you have rights over your personal information in addition to those in Section 9.

• What we collect is described in Section 3: account info, your uploaded materials and the data we derive from them, your study sessions, and usage and technical records.
• We do not sell your personal information, and we do not "share" it for cross-context behavioral advertising — in the specific senses those terms have under California law and other US state privacy laws. We never have, and we run no advertising.
• We don't offer financial incentives in exchange for your data.

Your rights include the right to know what we collect, to access and delete it, to correct it, and to not be discriminated against for exercising any of these. Because we don't sell or share your data, there's no opt-out to exercise — but you can still make any of these requests by emailing support@professor.ac. We'll verify the request against your account before acting on it.

12. Age

Professor Otto is for adults — 18 and over only. We don't knowingly collect data from anyone under 18. If you're a parent or guardian and believe your under-18 dependent has created an account, email us and we will delete it.

13. Changes to this policy

We'll post updates on this page and revise the "last updated" date at the top. Material changes — meaning real changes to what we collect, who we share it with, or how long we keep it — will also be surfaced in the app.

14. Contact

• General: support@professor.ac