A private, encrypted journal for your thoughts.
Tackling a personal problem, Notion is an overkill for recording an instant, Twitter (or X Now) is distracting and public, Notes app can get cluttered easily, you cant carry a physical book everywhere, basically needed a middle ground for me to write down my thoughts on the fly, or on the go.
If you want a more formal why
Most thoughts never make it out of your head. You either don't have someone to tell, or you're not comfortable sharing publicly. Over time, these pile up - ideas fade, frustrations linger, and experiences go unrecorded.
Writing is one of the simplest ways to process what's on your mind. Thoughtbook gives you a space to do that without worrying about who's reading.
Your thoughts are too precious to be lost in the void.
Thoughtbook is a privacy-first journaling app where you are the only person who can read your entries. Everything is local :)
- End-to-end encrypted — All data is encrypted locally on your device before it's ever persisted. Encryption keys are generated per-device and stored in the OS secure keychain (via
expo-secure-store). The storage layer (MMKV) is encrypted at rest. - Minimal by design — Open the app, write a thought, done. No accounts, no social features, no feeds.
- Offline-first — Everything runs and persists locally. No network calls required.
- Favorites — Star the thoughts that matter most and find them in a dedicated tab.
- Tags — Add
#hashtagsto your thoughts to categorize them (travel ideas, bucket lists, wishlists, etc.). - Calendar heatmap — See your writing history at a glance with a color-coded calendar showing how many thoughts you wrote each day.
- Streaks — Track your consecutive days of journaling to build a writing habit.
- Swipe actions — Swipe to favorite, edit, or delete thoughts without leaving the feed.
- Over-the-air updates — Get the latest improvements without waiting for app store reviews.
- On first launch, a 256-bit random key is generated using
expo-crypto. - That key is stored in the device's secure keychain (
expo-secure-store), accessible only when the device is unlocked. - All thought data is persisted to MMKV storage using that key for encryption at rest.
- No plaintext ever leaves the device.
For extra security, you can also use native Biometric authentication to unlock the app. Most phones provide application lock out of the box.
- Semantic search across entries (local, on-device)
- AI-assisted reflection — surface patterns, summarize periods, answer questions about your own journal
- Self-hosting support — bring your own backend, own your data completely
- Cross-device sync with E2EE
- React Native (Expo SDK 54)
- Expo Router for navigation
- Tamagui for UI
- Legend State for state management + persistence
- MMKV for encrypted local storage
- expo-crypto / expo-secure-store for key management
# Install dependencies
pnpm install
# Run on iOS
pnpm ios
# Run on Android
pnpm androidAGPLv3 — see LICENSE for details.