Last modified: July 30, 2026
Underline is an iOS app for keeping passages from paper books, developed by Melanie Chen. This policy explains what information the app collects, how that information is used, and what control you have over it. It covers the Underline app and the website at underline.ink.
If you have a question about anything in this policy, write to mel@underline.ink.
Please read the whole policy, but here are the questions people ask most.
Are photos of my book pages sent to an AI service?
No. Underline reads the page on your device using Apple's built-in text recognition. The photograph is stored in your own account so your captures sync between your devices, and it is not sent anywhere else.
Does Underline track me?
No. The app contains no analytics, attribution, or crash-reporting software of any kind. Nothing follows you across other apps or websites.
Does Underline sell my information?
No, and it will not.
What does get sent to an AI service?
Text. When you ask for an interpretation, put a question to Crowmeo, or ask for a recommendation, the passage and your question are sent to Anthropic's Claude API so it can answer.
Can I delete my data?
Yes. Anything you delete in the app is deleted from your account. To remove your account and everything in it, open Settings in the app and choose Delete account.
When you create an account, Underline stores your email address and an authentication record. If you sign in with Apple or Google, it receives whatever that service provides, which is normally an email address. If you use Apple's Hide My Email, it receives the relay address instead. Passwords are handled by the authentication provider and are never visible to Underline.
The passages you capture, the books and editions they belong to, page numbers and page labels, your margin notes, your binders and slips, your shelves, your reading streak, saved recommendations, and your conversations with Crowmeo.
When you capture a passage, the photograph of that page is kept so the passage can be read again or marked again later.
Underline keeps a short summary of themes you return to and books you have marked. It is used to choose which passage resurfaces each morning and to suggest what to read next.
Underline does not collect your location, your contacts, health data, advertising identifiers, or device identifiers used for tracking.
Reading a page is done entirely on your device. Apple's Vision framework recognises the words and Underline's own detector finds the marks you made. No network connection is required for this, and no image is transmitted.
Spoken reflections are also transcribed on your device. The audio is not sent to a server.
Your library is stored on your device and synced to an account hosted on Supabase, which provides the database, the sign-in system, and file storage. Database rows are protected by row-level security, so they are accessible only to your own account. Photographs of pages are stored in a private bucket under your user ID and are not publicly accessible.
Supabase hosts the database, authentication, and file storage. Its policy is at supabase.com/privacy.
Anthropic provides the Claude API behind interpretations, the Crowmeo conversation, highlight suggestions, and recommendations. Requests pass through a server that holds the API key, so the app never carries it. Only text is sent: the passage, your question, and related passages from your own library. Photographs are not sent. Under Anthropic's API terms this content is not used to train its models. Its policy is at anthropic.com/legal/privacy.
Google Books is used to look up book details. When you scan a barcode or search for a title, the ISBN or the text you typed is sent so the title, author, edition, and cover can be returned. No account information goes with it.
Webflow hosts underline.ink. If you give your email address to the waitlist on that site, Webflow stores it, and it is used only to tell you when Underline is available.
Information is used to run the app: to store your library and keep it in step across your devices, to choose a passage each morning, to produce interpretations and recommendations when you ask for them, and to send the reminders you have turned on. It is not used for advertising or profiling. It is not sold, and it is not given to anyone else for their own purposes.
Wherever you live, you may ask to see your information, to correct it, or to have it deleted.
Underline is not directed to children under 13 and does not knowingly collect information from them.
If this policy changes, the revised version will be posted on this page with a new date at the top. Significant changes will also be noted in the app.
© 2026 Underline · made with in Seattle 🌲