MarkDownViewer (mdview)

A simple, fast and lightweight standalone Markdown Viewer written in Rust.

Runs on Linux, macOS, Windows and Android — one renderer, one codebase.

Features

• GitHub Flavored Markdown rendering (tables, task lists, strikethrough)
• Syntax highlighting for 50+ programming languages
• Smart link handling (.md files open internally, others open in browser)
• Back/forward navigation between markdown files
• Live reload on file changes (desktop)
• Light and dark themes
• Inline image rendering

Usage

mdview <FILE.md>

Android

Install the APK from the latest release, then open a .md file from any file manager, or share one to mdview.

Tap 📁 to grant access to a folder rather than a single file. This is the recommended way in: documents inside a granted folder can link to each other, and their images resolve, because Android hands the app access to the whole tree rather than to one document. 📄 opens a single file, which is quicker but leaves links to sibling files unresolvable — Android gives no way to reach them.

Live reload is desktop-only: Android documents are read through the Storage Access Framework, which exposes no watchable path.

Keyboard Shortcuts

Shortcut	Action
Alt+Left	Navigate back
Alt+Right	Navigate forward
Ctrl+Q	Quit
F5	Manual refresh
Ctrl+T	Toggle theme

Releases

GitHub releases are built by .github/workflows/release.yml.

Create and push a version tag like v0.1.0 to trigger the pipeline automatically:

git tag v0.1.0
git push origin v0.1.0

The release workflow publishes:

• Windows zip archives
• macOS tar.gz archives for Intel and Apple Silicon
• Linux tar.gz archives
• Linux .deb packages for Debian and Ubuntu based distros
• Linux .rpm packages for Fedora, RHEL, Rocky, AlmaLinux, and openSUSE style distros
• Android mdview-<version>-android.apk (universal APK: arm64-v8a, armeabi-v7a, x86_64, x86)
• A SHA256SUMS.txt file for artifact verification

Building for Android

The Android port lives in android/. To build the APK locally:

# 1. Install Rust targets
rustup target add aarch64-linux-android armv7-linux-androideabi x86_64-linux-android i686-linux-android

# 2. Install cargo-ndk
cargo install cargo-ndk

# 3. Install Android SDK + NDK
sdkmanager "platform-tools" "platforms;android-34" "build-tools;34.0.0" "ndk;26.3.11579264"

# 4. Build the native libraries
cargo ndk \
    -t arm64-v8a \
    -t armeabi-v7a \
    -t x86_64 \
    -t x86 \
    -P 24 \
    -o android/app/build/intermediates/cargo-ndk-out \
    build --release

# 5. Build the APK
cd android
ANDROID_HOME=/opt/android-sdk JAVA_HOME=/usr/lib/jvm/java-21-openjdk-amd64 ./gradlew :app:assembleRelease

# 6. Install on a device
adb install -r app/build/outputs/apk/release/app-release.apk
adb shell am start -n eu.io_com.mdview/.MainActivity

The APK's versionName/versionCode are derived from version in Cargo.toml, so bumping the crate version is enough to bump the app.

Signing

assembleRelease falls back to the local debug keystore and prints a warning. That APK is fine for testing but not distributable: the debug key differs per machine, and Android refuses to upgrade an app whose signing key changed.

To produce a distributable APK, point the build at a real keystore:

export MDVIEW_KEYSTORE=/path/to/release.jks
export MDVIEW_KEYSTORE_PASSWORD=…
export MDVIEW_KEY_ALIAS=…
export MDVIEW_KEY_PASSWORD=…
./gradlew :app:assembleRelease

CI reads the same key from the repository secrets ANDROID_KEYSTORE_BASE64 (the .jks file, base64-encoded), ANDROID_KEYSTORE_PASSWORD, ANDROID_KEY_ALIAS and ANDROID_KEY_PASSWORD. Until those secrets are set the release workflow still builds an APK, but it is debug-signed and the job logs a warning saying so.

The app uses androidx.games:games-activity:4.4.0 to host the eframe/egui rendering surface, and the jni crate for the small set of JNI calls needed to bridge between Rust and Kotlin (file picker, intent data, etc.).

License

GPLv3 — see LICENSE for details.