# Happybook

> Happybook is a progressive web app for building notebooks out of PDFs. Add a PDF to start a notebook, add more PDFs to it, highlight passages, and create cross-links between locations in different PDFs. Everything works offline; signing in (passkeys) syncs notebooks across devices.

## What it does

- Notebooks: each notebook is a collection of PDFs plus your highlights and links.
- Highlights: select text in a PDF and highlight it; highlights persist per notebook.
- Cross-links: select text or a spot in one PDF and link it to a page, passage, or point in another PDF in the same notebook. Links are navigable in both directions.
- Offline-first: the app and your documents live on your device; no account is required to use it.
- Sync: sign in with a passkey to back up notebooks and sync them across devices.

## URLs

- App: https://app.happybook.proc.io
- Marketing: https://happybook.proc.io

## Technical notes

- Local storage: IndexedDB for structured data, OPFS for PDF bytes.
- Sync: last-write-wins record sync over HTTPS; PDF blobs are content-addressed by SHA-256.
- Auth: WebAuthn passkeys via AuthGravity; no passwords.