OpenCallShield

English · Español · Português · Français · Deutsch · Русский · 中文 · 日本語 · 한국어

Open source (MIT) Android app that blocks SPAM calls using CallScreeningService (Android 10+), with a local Room database, a detection rules engine and sync with a public collaborative list hosted on GitHub.

A privacy-first, decentralized alternative to Truecaller.

⬇️ Download

• Google Play: https://play.google.com/store/apps/details?id=com.jhonsu01.opencallshield
• Direct APK: download the .apk from Releases.

📱 Screenshots

Screenshots in every language are in playstore/screenshots/.

✨ Features

• Automatic blocking through CallScreeningService (reject or silence).
• Rules engine: known contact → allow; reported number → block; blacklisted prefix → block; number not in contacts → optional.
• Block by country with one tap on the flag (no prefixes to type).
• Local Room database of reported numbers.
• Sync with a public JSON on GitHub (daily via WorkManager + manual).
• Reports and history of filtered calls (add / remove numbers with one tap).
• 9 languages: English, Español, Português, Français, Deutsch, Русский, 中文, 日本語, 한국어 — pick one from the 🌐 icon in the app or from Android's per-app language settings.
• UI in Jetpack Compose (Material 3).

🏗️ Stack

Kotlin · Jetpack Compose (Material 3) · Room · WorkManager · AppCompat (per-app language) · MVVM · CallScreeningService · targetSdk 36 (Android 16)

📦 Build

# Requires JDK 17 and the Android SDK (compileSdk 36)
./gradlew assembleDebug      # installable debug APK
./gradlew assembleRelease    # release APK (needs signing)
./gradlew bundleRelease      # AAB for Google Play

Outputs are in app/build/outputs/.

📲 Usage

1. Install the app.
2. Grant the contacts permission (so your contacts are never blocked).
3. Tap "Set as call screening app" and accept the role in Android.
4. Adjust the rules, pick countries to block and/or sync the collaborative list.

🌐 Collaborative list

The app syncs from spam_numbers.json in this repository:

https://raw.githubusercontent.com/jhonsu01/OpenCallShield/main/spam_numbers.json

Format:

{
  "version": "1.0",
  "updated_at": "2026-01-01",
  "numbers": [
    { "number": "+1234567890", "reports": 120, "tag": "scam" }
  ]
}

The URL can be changed from the app (Advanced settings), so anyone can run their own list (guide, in Spanish).

🔑 Contributing from the app (optional GitHub sign-in)

From ⋮ → Collaborate you can sign in with GitHub and then, in SPAM list, tap "Contribute to the public database": the app opens an Issue in this repo with your reported numbers as JSON, ready to merge into spam_numbers.json. Signing in is optional: the app works fully without it.

Two ways to sign in (no server/backend):

Option A — OAuth Device Flow (recommended)

1. On GitHub: Settings → Developer settings → OAuth Apps → New OAuth App, then enable Device Flow.
2. Copy the Client ID (it is public, not a secret).
3. In the app → Collaborate → paste the Client ID, tap Connect and enter the code at github.com/login/device.

Option B — Personal access token (PAT)

1. GitHub → Settings → Developer settings → Personal access tokens → create one with the public_repo scope.
2. In the app → Collaborate → paste it and tap Connect with token.

The token is stored encrypted on the device (EncryptedSharedPreferences) and is only sent to the GitHub API.

🛠️ Reviewing contributions (maintainer)

Contributions arrive as Issues with a JSON block. Copy the numbers into spam_numbers.json, update "updated_at" and commit with Closes #N.

🔓 License

MIT — see LICENSE. Privacy policy: PRIVACY.md.

❤️ Support the project

OpenCallShield is free and open source. If you find it useful, you can support its development: