Privacy policy

Postbook turns what you share into books and emails them to your Kindle. It keeps only what it needs to do that, sells nothing, shows no ads and has no analytics or tracking.

What we store

• Your Kindle's email address, and the email address for notices if you add one.
• What you share: the links, their titles, and whether each book was sent. This list is kept until you delete your account, so the app can show your recent books.
• Copies of pages you share, used to build the book. They're deleted after 7 days.
• Links you open on postbook.app, and links you paste or copy into the app (on Android, automatically only if you turn on Show links I copy): we fetch the page to show its title and opening lines, and keep that for up to 24 hours. Links with a password-like part in their address aren't kept.
• The covers of your last 60 books, so the app can show them.
• The books themselves, for 60 days, so you can send one again. They're deleted with your account.
• Summaries and critiques, if you turn them on, kept for up to 7 days so a book that's sent again doesn't pay for them twice.
• Comments, if you turn them on: the top comments on what you share (each commenter's display name and handle as the site shows them, the text and the date), with their summary. Kept until the book is sent, for at most 7 days. Email addresses and phone numbers in comments are removed.
• Your devices: a name (such as "iPhone") and a hash of each device's key.
• A salted hash of your network address, to limit sign-ups and sign-in attempts. We don't store the address itself.
• Your subscription's status (product, renewal and expiry dates) from Apple. We never see your payment details.

Who processes it

• Cloudflare runs our servers, database, file storage and email.
• Amazon receives each book at your Kindle's address, through Send to Kindle.
• FxTwitter (a public service) is asked for the posts you share.
• The websites you share are fetched to read their articles.
• AI services make the covers: Anthropic gets the book's title and an excerpt to come up with an image idea, and xAI or OpenAI draws it.
• Summaries and critiques are off unless you turn them on. Then the book's whole text goes to Anthropic.
• Comments are off unless you turn them on. Then the chosen comments and the opening of the post or article go to Anthropic for a short summary, without names, handles or like counts. Comments from pages you shared from Safari are put in the book but never sent to Anthropic. We read comments only from public sources, never LinkedIn's or Meta's servers.

These services process the data only to provide their part of Postbook.

Deleting your data

Delete your account in the app (Settings → Delete account), or without the app. Everything above is deleted at once, except copies of pages and notes, which expire within 7 days. To stop the free books being claimed again by a new account, we keep a keyed hash of your Kindle's address (not the address itself) for 12 months, then delete it. We can match it against an address if one is given to us, but we can't read the address from it. Deleting your account doesn't cancel an App Store subscription: cancel it in your Apple account's subscriptions.

Children

Postbook isn't directed at children under 13.

Contact

Questions about your data: support@postbook.app.