Privacy Policy

This policy explains what information Kindle Book Studio ("we," "us") collects when you use our app, how we use it, and the choices you have. We built this app to help you write books — we try to collect no more than what's needed to make that work well.

Information we collect

• Account information: your email address, and if you sign in with Google, your Google account email and name.
• Your content: the manuscripts, chat messages, and book metadata (titles, chapters) you create in the app.
• Usage data: basic technical logs (e.g. timestamps, error logs) used to keep the app running reliably.
• Payment information: if and when paid plans are active, payment is processed entirely by Stripe — we never see or store your full card details ourselves.

How we use your information

• To provide the core writing experience — your messages and manuscript content are sent to Anthropic's Claude API to power Quill, your AI co-writer.
• To authenticate your account and keep your books synced across devices, via Supabase.
• To send you account-related emails (confirmation, password reset) via Resend.
• To process payments, if you're on a paid plan, via Stripe.
• To maintain and improve the reliability of the app.

What we don't do

• We don't sell your personal information or manuscript content to third parties.
• We don't use your manuscript content to train AI models.
• We don't show ads in the app.

Third-party services we use

We rely on a small number of trusted providers to run Kindle Book Studio:

• Anthropic — powers Quill, the AI writing assistant. Your messages and manuscript context are sent to Anthropic's API to generate responses.
• Supabase — handles authentication and account data.
• Resend — sends transactional emails (signup confirmation, etc.).
• Stripe — processes payments, when paid plans are active.
• Railway — hosts our application and stores your manuscript files.

Each of these providers has its own privacy practices governing data they process on our behalf.

Data retention

We retain your account and manuscript data for as long as your account is active. If you delete your account, we remove your personal data and manuscripts within a reasonable period, except where we're required to retain certain records (e.g. payment records) for legal or accounting purposes.

Your rights

Depending on where you live, you may have rights to access, correct, export, or delete your personal information. You can manage most of this yourself from within the app, or contact us directly using the details below.

Cookies

We use a minimal set of cookies/local storage strictly necessary for keeping you signed in. We don't use tracking or advertising cookies.

Changes to this policy

We may update this policy from time to time. If we make material changes, we'll notify users via email or an in-app notice.

Contact us

Questions about this policy? Reach us at support@kindlebookstudio.com.