Privacy

Backfill is a free, non-commercial personal project, built by Rutwik Pasumarthi and put online for anyone who wants to give it a try.

It stores your email address and what you have learned, and it sends the text you submit to a language model provider so lessons can be written. It does not sell anything, run ads, track you across the web, or take payment details.

Your account. Your email address, and an identifier from whichever sign-in method you used. If you sign in with a provider that shares a display name, that is stored too.

What you submit. Links you paste, the extracted text of files you upload, goals you type, questions you ask on a highlight, and any feedback you send.

What you do. The courses you create, the steps in them, your quiz answers and scores, which concepts you have demonstrated, and your highlights and notes.

Server logs. Ordinary request logs kept by the host, which include IP addresses. Not used to build a profile of you.

Backfill cannot write a lesson without sending your text to a model. These are everyone it reaches:

• SupabaseAuthentication and the database. Holds your email address, your login session, and everything the app stores about your learning.
• VercelHosting. Serves the site and keeps short-lived server logs of requests, which include IP addresses.
• OpenRouterRoutes text to the model that writes modules. Receives whatever you submit for teaching — pasted links, the text of files you upload, your stated goals, and the questions you ask on a highlight.
• The model provider behind OpenRouterCurrently Moonshot AI, whose Kimi model writes the modules. Receives the same text OpenRouter does. Changing the configured model changes who this is.

Each has its own terms and its own retention. Nobody else receives your data, and it is never sold or shared for advertising.

Lessons are written once per concept and reused by everyone, which is what keeps this affordable to run. A lesson generated because you asked for it goes into a shared library and is served to other people learning the same thing.

Those lessons contain no personal information — not your name, your email or your progress — but they are derived from what you submitted. Deleting your account does not withdraw them, because by then they are content other people are learning from. Do not paste anything confidential.

One cookie, holding your sign-in session, so you are not asked to log in on every page. There are no analytics, advertising or third-party tracking cookies, which is why there is no consent banner.

Your account and learning history are kept until you ask for them to be deleted. Server logs are kept only as long as the host keeps them, which is a matter of days.

Email rutwikpasumarthi@gmail.com and ask. Your account, your courses, your progress, your highlights and your feedback will be deleted. You can also ask for a copy of what is stored about you, or for something to be corrected.

The one exception is the shared lessons described above, which stay in the library because other people are using them.

This is not intended for children under 13, and accounts are not knowingly created for them.

If what is collected or who it goes to changes, this page changes and the date at the top moves.

Anything about your data: rutwikpasumarthi@gmail.com.