# Folio

> Free, open source note-taking app for Android tablets and pens. Write by hand with pressure-sensitive brushes, annotate PDFs and EPUBs, convert handwriting to text. Offline, no account.

Folio is a free, open source (Apache 2.0) Android app for pen tablets and phones: handwriting with pressure-sensitive brushes, page templates and an infinite canvas, a PDF and EPUB reader with annotations and OCR, handwriting to text, and Excalidraw live boards for calls. It works offline, with no account and no ads. Source code: https://github.com/allient/folio. Every page is also available as Markdown by sending `Accept: text/markdown`.

## Product

- [Folio: Handwriting Notes & PDF Annotation App for Android Tablets](https://folio.allient.io/index.md): Free, open source note-taking app for Android tablets and pens. Write by hand with pressure-sensitive brushes, annotate PDFs and EPUBs, convert handwriting to text. Offline, no account.
- [Brand](https://folio.allient.io/brand/index.md): Folio logo, colours, type and how the app uses them.
- [Privacy policy · Folio](https://folio.allient.io/privacy/index.md): How Folio handles your notes, books and recordings: everything stays on your device.

## Developer docs

- [Ink rendering research](https://folio.allient.io/architecture/ink-rendering-research/index.md): How Folio renders handwriting on Android: Jetpack Ink, front-buffered wet ink and the options reviewed for low-latency stylus drawing.
- [Jetpack Ink implementation and code review](https://folio.allient.io/architecture/jetpack-ink-implementation/index.md): How Folio uses Jetpack Ink for low-latency, pressure-sensitive handwriting on Android, with a code review of the integration.
- [Local storage and portable backups](https://folio.allient.io/architecture/local-storage/index.md): Where Folio keeps notebooks and books on the device, how Trash and smart backups work, and the limits on importing files.
- [Modules and the iOS path](https://folio.allient.io/architecture/modules/index.md): How Folio's Kotlin Multiplatform code is split today, the rules that keep it portable, and the order for an iOS port.
- [Folio portable format](https://folio.allient.io/architecture/portable-format/index.md): The open .folio notebook format: a ZIP archive with Zstandard-compressed JSON, its schemas, assets and legacy .knotes support.
- [PDF and EPUB reader](https://folio.allient.io/architecture/reader/index.md): How Folio’s PDF and EPUB reader works: rendering, highlights and margin notes, search, OCR, bookmarks and export.
- [SQLite schema migrations](https://folio.allient.io/architecture/sqlite-migrations/index.md): Rules for changing Folio’s on-device SQLite databases safely, without risking a user’s library.
- [BOOX-inspired notes: implementation coverage](https://folio.allient.io/features/boox-feature-coverage/index.md): Which handwritten-notes workflows Folio covers: toolbar, tool rail, notebooks, page navigation and more.
- [Canvas tools review — 2026-10-16](https://folio.allient.io/features/canvas-tools-review/index.md): Review of Folio’s canvas tools: pens, erasers, lasso, shapes, fill, layers and zoom, with what was fixed.
- [Live boards](https://folio.allient.io/features/live-boards/index.md): Excalidraw boards inside Folio with Folio's pen filters, a Live tab in the library, and live sessions for video calls.
- [Ruler and zoom window](https://folio.allient.io/features/ruler-and-zoom-window/index.md): Folio’s ruler for straight lines and angles, and the zoom window for writing small details with the pen.
- [Tables, stickers and sticky notes](https://folio.allient.io/features/tables-stickers-notes/index.md): Tables, stickers and sticky notes on Folio pages: how they work and how they are stored.
- [MNP1095 writing crash: Jetpack Ink mesh rendering](https://folio.allient.io/investigations/mnp1095-mesh-crash/index.md): Why writing crashed Folio on an Android 14 pen tablet (Jetpack Ink mesh rendering) and how path rendering fixed it.
- [Publish on Google Play](https://folio.allient.io/publishing/google-play/index.md): Step-by-step guide to publishing Folio on Google Play, from the first upload to routine releases.
- [Play Console answers](https://folio.allient.io/publishing/play-console-answers/index.md): Copy-ready store listing text and the answers for every Play Console form.
- [Planned preferences and languages (not implemented)](https://folio.allient.io/roadmap/planned-preferences/index.md): Preferences and app languages planned for Folio but not built yet, and why they wait.
- [Responsive layout: possible improvements](https://folio.allient.io/roadmap/responsive-improvements/index.md): Layout problems found when checking Folio in landscape and at phone size, kept for later.
- [Mirroring the tablet](https://folio.allient.io/testing/mirroring/index.md): See and control the physical tablet from the Mac while testing Folio.
- [Validation — 2026-10-16](https://folio.allient.io/testing/validation/index.md): Test results for Folio on the Android tablet emulator: builds, instrumented tests and UI flows.

## Optional

- [All pages in one file](https://folio.allient.io/llms-full.txt)
- [.folio archive agent skill](https://folio.allient.io/.well-known/agent-skills/folio-archive/SKILL.md): read and write Folio notebook files
- [Notebook JSON schema](https://folio.allient.io/schemas/folio-notebook-v2.schema.json)