Folio

A quiet, local-first notebook for handwriting, sketches, maths, and PDFs.

Folio is a native Android notebook built with Kotlin and Jetpack Compose. Write with a stylus or finger, keep pages organized, and take your notebooks with you in .folio backups.

Features

• Pressure-sensitive handwriting, drawing tools, and undo/redo
• Writing follow that measures your lines from the ink, holds still for corrections, and offers one-tap or automatic line return, plus a pinned peek view (hold to glance, tap to keep open)
• Typed notes, photos, and PDF annotation
• Long responses: pinned questions, plans, linked drafts and marked copies, side-by-side comparison, and feedback actions
• Ruled, dotted, grid, maths, and infinite-canvas pages
• Graph tool: centred or corner axes, optional grid, ticks, unit numbers and x/y labels
• Page bookmarks, search, and notebook organization
• Dedicated study timer: standalone or notebook-linked sessions, reflections, history, and Focal sync
• Reference view: a read-only PDF pane with contents, text search, page jump, zoom/fit and link following
• Export pages as PDF or PNG; save compact .folio backups with undo history, or use incremental automatic library backups (details)
• Make it yours: your own accent colour, app text size, toolbar layout, quick ink colours, saved tool presets and notebook covers
• Core notebook works offline; Android 8.0 and newer

Get Folio

Download the latest APK from GitHub Releases.

Experimental builds are available from the Folio server. In Settings → Account & updates, enable Experimental builds to check that server; leave it off for stable GitHub releases. Server setup and publishing are documented in docs/release-server.md.

Build

Requires JDK 17 and Android SDK 36.

./gradlew :app:assembleDebug

For repeated local builds, keep app/build and the Gradle caches: avoid clean unless diagnosing a build problem. On Windows, use .\build.ps1 -Tasks ':app:assembleDebug' for the same build without lint.

CI builds and publishes signed R8 releases on pushes to main or manual dispatch. Run local build and lint checks with:

./gradlew :app:assembleDebug :app:lintDebug

On the configured VPS, run bash ./build.sh to make a signed experimental build, then answer y to publish it. Each run gets a new version code even without a new commit (commitCount × 10000 + localBuildNumber) and a name such as 2.1.7-exp.2. Stable Gradle/CI builds use commitCount × 10000; the next stable commit therefore supersedes the preceding experimental builds.

Version numbers are supplied lazily to the APK outputs. Focal connection settings are generated separately from version metadata, so changing a commit or experimental build number can reuse Kotlin/Java compilation in both debug and release builds. Gradle's configuration and build caches remain enabled. To inspect local task timings, add --profile to either build command; reports are written to build/reports/profile/.