Privacy Policy — BookBuddy

This Privacy Policy explains what personal data BookBuddy (“we”, “us”) collects when you use bookbuddy.me, why we collect it, who we share it with, and what rights you have under the EU General Data Protection Regulation (GDPR).

1. Controller

The controller responsible for the processing of your personal data is the operator of bookbuddy.me. Full contact details are listed in our Impressum. For any questions about this Privacy Policy or to exercise your rights under GDPR, please use the contact information provided there.

2. Data we collect

2.1 Account data (when you sign in)

Your email address, name, and profile picture from your Google account (via Google OAuth)
A unique account identifier
Account creation date and last sign-in date

2.2 Content you upload or generate

EPUB book files you upload
Extracted book text and metadata (title, author, cover image)
Chat messages you send to the AI assistant and the AI’s responses
Highlights, favorites, and notes you create
Voice recordings you submit for transcription (these are sent to OpenAI for transcription and not stored long-term by us)

2.3 Usage data

Your reading progress (current page, words read) for each book
Device and font preferences
Daily quota usage (number of AI requests, uploads, transcriptions)
Technical logs (timestamps, error events, request paths) used to diagnose issues

3. Why we use your data (legal basis)

To provide the service — storing your books, answering your questions, and syncing reading progress (Art. 6(1)(b) GDPR — performance of a contract).
To keep the service running — logging errors, enforcing rate limits, preventing abuse (Art. 6(1)(f) GDPR — legitimate interests).
To sign you in via Google — based on your consent at the OAuth screen (Art. 6(1)(a) GDPR).

4. Who we share data with (processors)

We do not sell your data. We rely on the following service providers, each acting as a data processor on our behalf:

Supabase (database, file storage, authentication) — data is hosted in the EU. See supabase.com/privacy.
Google Cloud Run (application hosting in europe-west1) and Google AI / Gemini (for AI responses about your books). See Google’s privacy policy. Book passages relevant to your question are sent to Gemini to generate the answer.
OpenAI (voice transcription via the gpt-4o-transcribe model). Your voice recording is sent to OpenAI’s API and processed under their data-processing terms. See openai.com/policies/privacy-policy.
Langfuse (AI request tracing for performance monitoring). See langfuse.com/security.
PostHog (product analytics and session replay) — hosted on PostHog Cloud EU in Frankfurt. See Section 6 for what is collected and posthog.com/privacy.
STRATO (domain registration, DNS, and email hosting) — a German provider; data is hosted in the EU. See strato.de/datenschutz.

Some of these providers (Google, OpenAI) may process data outside the EU, primarily in the United States. Transfers are protected by Standard Contractual Clauses and, where applicable, the EU–U.S. Data Privacy Framework.

5. How long we keep your data

We keep your account data and content for as long as your account exists. Voice recordings are not retained after transcription. Technical logs are retained for up to 30 days. When you delete your account (see Section 7), we permanently delete your books, conversations, highlights, reading progress, and account record within 30 days.

6. Cookies and tracking

We use essential cookies required for authentication (session tokens issued by Supabase Auth). We do not use advertising cookies.

To understand how BookBuddy is used and to fix problems, we use PostHog, hosted in the EU (Frankfurt). Requests to PostHog go through our own domain, so no third-party domain is contacted directly.

Visitors who are not signed in are measured without cookies or browser storage. PostHog derives a daily, non-reversible hash from your IP address and browser and discards the IP; we cannot recognise you across days.
When you sign in, PostHog stores a first-party cookie so that your usage can be attributed to your account (user ID and email address), and it records your sessions: the pages you see, including the book text on screen, your chat messages and what you type, plus clicks, scrolling and errors. Passwords are always masked. We use these recordings only to understand how BookBuddy is used and to fix problems.

Analytics data is kept for one year and session recordings for 30 days. You can object to this processing at any time via the contact details in our Impressum; we will stop attributing usage to your account.

7. Your rights under GDPR

You have the right to:

Access the personal data we hold about you
Rectify inaccurate data
Erase your data (“right to be forgotten”)
Restrict processing
Receive a copy of your data in a portable format
Object to processing based on legitimate interests
Withdraw consent at any time (this does not affect lawful processing that occurred before withdrawal)
Lodge a complaint with a supervisory authority — for users in Germany, this is your state data protection authority (Landesdatenschutzbeauftragter).

To exercise any of these rights, sign in and go to Settings → Danger zone for self-serve account deletion, or contact us using the details in our Impressum.

8. Security

We use industry-standard measures to protect your data, including TLS encryption in transit, encrypted storage, role-based database access controls (PostgreSQL Row-Level Security), and short-lived signed URLs for file access.

9. Children

BookBuddy is not directed at children under 16. If you become aware that a child has signed up without parental consent, please contact us and we will delete the account.

10. Changes to this policy

We may update this Privacy Policy from time to time. Material changes will be announced in-app or by email. The “Last updated” date at the top of this page reflects the most recent revision.