Last Updated: September 30, 2026
DualBook ('we', 'our', or 'us') is an independent product operated by its founder from Vietnam. This Privacy Policy explains what we collect, how we use it, and who else sees it when you use the service. Questions go to privacy@dualbook.net.
We collect information you provide directly to us, including your name, email address, and uploaded content. We also automatically collect certain information about your device and usage of our service, including IP address, browser type, and access times.
We use your information to provide, maintain, and improve our services; process your transactions; send you technical notices and support messages; respond to your comments and questions; and detect and prevent fraud and abuse.
We use industry-standard security measures to protect your information. Your uploaded books and translations are stored securely using encryption. We retain your information only as long as necessary to provide our services or as required by law.
When you upload an EPUB we extract its text and store both the original file and the extracted text so translation jobs can run and you can re-read results later. To translate or summarise a book, that text is sent in chunks to our AI provider — the Google Gemini API — which processes it and returns the translation. Text-to-speech works the same way. Your books are stored on our own infrastructure, are readable only by your account, and are not used to train any model. Deleting a book removes its file, extracted text, and generated output; deleting your account removes all of it.
We rely on a small number of processors: the Google Gemini API for translation, summaries, and text-to-speech; Stripe for payments on the web; Apple (App Store) and Google (Google Play) for purchases in the mobile apps; Google Sign-In and Sign in with Apple for authentication; and Google Analytics for usage measurement. Apple, Google and Stripe handle your payment details. We receive only a record of each purchase (the product, the date and a transaction ID) and never your card number. Each has its own privacy policy and we encourage you to review them. We do not sell your personal information or your uploaded content to anyone.
We implement appropriate technical and organizational measures to protect your personal information. However, no method of transmission over the Internet or electronic storage is 100% secure, and we cannot guarantee absolute security.
You have the right to access, update, or delete your personal information. You can do this through your account settings or by contacting us. You also have the right to opt out of marketing communications.
We use cookies and similar tracking technologies to track activity on our service and hold certain information. You can instruct your browser to refuse all cookies or to indicate when a cookie is being sent.
We retain your personal information and uploaded content for as long as your account is active or as needed to provide you services. You may delete your books and account at any time through your account settings.
Our service is not intended for children under 13 years of age. We do not knowingly collect personal information from children under 13. If you are a parent or guardian and believe your child has provided us with personal information, please contact us.
We may update this Privacy Policy from time to time. We will notify you of any changes by posting the new Privacy Policy on this page and updating the 'Last Updated' date.
If you have any questions about this Privacy Policy, contact us through our contact page or email us at privacy@dualbook.net.
