Digital Habits: Blocker Android

Block distracting websites and apps with scheduled or one-off blocks. Stay focused on what matters.

Built by computer scientists at the University of Oxford (Dr Ulrik Lyngs) and the University of Maastricht (Dr Konrad Kollnig), as part of the Reduce Digital Distraction project (digitalhabits.org).

Features

• App Blocking — Detects blocked apps via Accessibility Service and returns you to the home screen
• Website Blocking — Blocks websites in Firefox, Chrome, Brave, Vanadium, and other Chromium-based browsers
• Flexible Blocklists — Create multiple schedules with custom sets of blocked apps and websites
• One-Off Blocks — Quick blocks for immediate focus sessions
• Scheduled Blocks — Set recurring blocks on specific days/times (e.g., block social media Mon–Fri 9am–5pm)
• Override Protection — Configurable word-entry friction prevents impulsive unblocking
• Tamper Protection — Enabled by default with a 10-word minimum (configurable in the settings menu; existing saved preferences are retained): while a block is active, opening the blocker's App info page (Force stop, Uninstall) or its accessibility settings resets Settings navigation before showing a friction gate. The required word count is the maximum of this minimum and all active schedules' word counts. Completion allows Settings access for one minute without pausing any schedule; lowering or disabling protection requires the same word count. Completing or cancelling the gate does not reopen the protected page. The earlier Back/Recents navigation reset was tested on a Pixel 9; the independent access window still needs device validation. Other Settings implementations may differ, and rapid taps before detection remain possible.
• Boot Persistence — Schedules resume automatically after device restart
• Material You — Modern Material 3 design with dynamic colors

Architecture

flowchart TB
    subgraph App["Android App (Kotlin / Jetpack Compose)"]
        UI[User Interface]
        Data[Room Database + DataStore]
        Scheduler[Schedule Manager]
    end

    subgraph Service["Accessibility Service"]
        AppWatcher[App Watcher]
        WebWatcher[Browser URL Watcher]
    end

    subgraph Receiver["Broadcast Receivers"]
        Boot[Boot Receiver]
        Alarm[Alarm Receiver]
    end

    subgraph System["Android System"]
        Apps[Running Apps]
        Browsers[Browser URL Bar]
        Home[Home Screen]
    end

    UI --> Data
    UI --> Scheduler
    Scheduler --> Alarm
    Boot --> Scheduler
    Alarm --> Service
    AppWatcher -->|detect blocked app| Apps
    AppWatcher -->|redirect to| Home
    WebWatcher -->|detect blocked URL| Browsers
    WebWatcher -->|redirect to digitalhabits.org| Browsers

How It Works

App Blocking

Digital Habits: Blocker uses Android's Accessibility Service to monitor which app is in the foreground. When a blocked app is detected, the user is immediately returned to the home screen.

Component	Role
Accessibility Service	Detects foreground app changes via onAccessibilityEvent
Home redirect	Launches the default launcher intent to return user to home screen

Website Blocking

The Accessibility Service also monitors the URL bar of supported browsers. When a blocked domain is detected, the browser is redirected to digitalhabits.org.

Browser	Support
Firefox	✅ URL bar monitoring via Accessibility
Chrome	✅ URL bar monitoring via Accessibility
Brave	✅ URL bar monitoring via Accessibility
Vanadium	✅ URL bar monitoring via Accessibility
Other Chromium-based	✅ URL bar monitoring via Accessibility

Schedule Management

Schedules define which apps and websites are blocked and when. Each schedule can be configured with:

• Manual activation — Start/stop blocks on demand
• Daily schedule — Block during specific hours every day
• Weekly schedule — Block during specific hours on selected days
• Override friction — Require typing a configurable number of random words before disabling

Schedules are persisted via Room database and survive app restarts. A boot receiver re-registers alarms on device restart.

Permissions

Permission	Purpose
Accessibility Service	Required. Detects app launches and browser URL navigation
Notifications	Shows alerts when content is blocked
Battery Optimization Exemption	Ensures reliable background operation
Receive Boot Completed	Restores schedules after device restart

Project Structure

ReDDBlockAndroid/
├── app/src/main/
│   ├── AndroidManifest.xml           # App manifest & permissions
│   └── java/net/kollnig/reddblockandroid/
│       ├── MainActivity.kt           # Main entry point
│       ├── ReDDBlockApp.kt           # Application class
│       ├── data/                     # Room database & data models
│       ├── receiver/                 # Boot & alarm broadcast receivers
│       ├── schedule/                 # Schedule management logic
│       ├── service/                  # Accessibility service
│       ├── ui/                       # Jetpack Compose UI screens
│       └── util/                     # Utility functions
├── build.gradle                      # Project-level build config
├── app/build.gradle                  # App-level build config & dependencies
├── gradle/                           # Gradle wrapper
└── settings.gradle                   # Project settings

Local Development

Prerequisites

• Android Studio (latest stable)
• JDK 17+
• Android SDK 34+

Getting Started

# Clone the repository
git clone <repo-url>
cd ReDDBlockAndroid

# Build debug APK
./gradlew assembleDebug

# Install on connected device
./gradlew installDebug

Or open the project in Android Studio and run directly on a connected device or emulator.

Building

# Debug build
./gradlew assembleDebug

# Release build
./gradlew assembleRelease

Requirements

• Android: 7.0+ (API 24, Nougat or later)

Acknowledgments

This project is based on Reef by Pranav Purwar, licensed under the MIT License.

License

MIT

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Made with ♥ by digitalhabits.org