What Sourcebook accesses, stores, and never does.

Sourcebook is a Chrome extension that exports the sources of the NotebookLM notebook open in your browser as a zip archive. It is designed so that your data never leaves your computer except to be fetched from Google.

What the extension accesses

Your NotebookLM session. To list and download your sources, Sourcebook reads the session token that NotebookLM's web page already holds and uses it to call NotebookLM's own web API, exactly as the page itself does. The token is read into memory when you use the extension and is never written to disk, synced, or sent anywhere other than notebook.google.com.
Your notebook's sources. Source content is downloaded from Google (notebook.google.com and *.googleusercontent.com) directly to your computer and packaged into a zip that Chrome saves where you choose.

What the extension stores

Export history, per notebook, in Chrome's local extension storage: for each exported source, a content fingerprint (a SHA-256 hash), the time of export, and the source's title. This powers the New / Changed / Exported labels. No source content is stored. Delete it at any time with Forget export history for this notebook in the popup, or by removing the extension.
Popup preferences — compression choice, "ask where to save", "only new or changed".

What the extension does not do

It does not collect analytics, telemetry, or crash reports.
It does not send any data to the developer or to any third party.
It does not use remote code; everything runs from the packaged files.
It does not read any website other than notebook.google.com and notebooklm.google.com.

Permissions

Permission	Why
`downloads`	Save the archive you asked for.
`offscreen`	Build the archive in a background page.
`storage`	Keep the export history and preferences described above.
`alarms`	Free memory after an export finishes.
Host access to `notebook.google.com`, `notebooklm.google.com`, `*.googleusercontent.com`	Read the source list and download the files, using your existing sign-in.

Contact

Questions about this policy: open an issue in the project repository.