Show HN: ProjectDiscoverys Subfinder > Android App in

3 hours ago 1

A simple and powerful Android application for passive subdomain enumeration, based on the ProjectDiscovery Subfinder tool.

Passive Enumeration: Uses only passive sources (no active scanning)
Multiple Sources: Queries 5 different sources:
- crt.sh (Certificate Transparency logs)
- HackerTarget API
- ThreatCrowd API
- AlienVault OTX
- RapidDNS
Material Design UI: Clean, modern interface
Fast & Parallel: All sources queried simultaneously using Kotlin coroutines
Export Results: Share/export subdomain lists as text files
No API Keys Required: All sources are free and don't require authentication

The app implements the same core logic as Subfinder:

Input: User enters a domain (e.g., example.com)
Query: App queries multiple passive DNS/security sources in parallel
Extract: Subdomains are extracted from API responses
Deduplicate: All results are combined and duplicates removed
Display: Sorted list of unique subdomains shown in the app

Android Studio (latest version) OR
Android SDK Command Line Tools
JDK 8 or higher

Method 1: Using Android Studio

Open Android Studio
Click "Open Project"
Navigate to the subfinder-android folder
Wait for Gradle sync to complete
Click Build → Build Bundle(s) / APK(s) → Build APK(s)
APK will be generated in: app/build/outputs/apk/debug/app-debug.apk

Method 2: Using Command Line

# Navigate to the project directory cd subfinder-android # Make gradlew executable (Linux/Mac) chmod +x gradlew # Build debug APK ./gradlew assembleDebug # For release APK (requires signing) ./gradlew assembleRelease

The APK will be located at:

Debug: app/build/outputs/apk/debug/app-debug.apk
Release: app/build/outputs/apk/release/app-release-unsigned.apk

Method 3: Direct Gradle Build (if you have gradle installed)

cd subfinder-android gradle assembleDebug

Transfer the APK to your device
Enable "Install from Unknown Sources" in Settings
Open the APK file and tap Install

adb install app/build/outputs/apk/debug/app-debug.apk

Launch the app
Enter a domain name (e.g., hackerone.com)
Tap "Start Scan"
Wait for results (typically 10-30 seconds)
View the discovered subdomains
Tap "Export" to share/save the results

Android 7.0 (API Level 24) or higher
Internet connection

SubdomainFinder (Main Engine) ├── SubdomainSource (Interface) │ ├── CrtShSource │ ├── HackerTargetSource │ ├── ThreatCrowdSource │ ├── AlienVaultSource │ └── RapidDnsSource ├── MainActivity (UI) └── SubdomainAdapter (RecyclerView)

Language: Kotlin
UI: Material Design 3
Async: Kotlin Coroutines
HTTP: OkHttp3
JSON: org.json
Min SDK: 24 (Android 7.0)
Target SDK: 34 (Android 14)

Comparison with Original Subfinder

Feature Original Subfinder This Android App

Sources	40+ sources	5 free sources
API Keys	Optional	Not required
Platform	CLI (Linux/Mac/Windows)	Android Mobile
Language	Go	Kotlin
DNS Resolution	Yes	No
Wildcard Filtering	Yes	No
Speed	Very Fast	Fast
UI	Command Line	Material Design GUI

Fewer sources than the original tool (5 vs 40+)
No DNS resolution verification
No wildcard filtering
No recursive enumeration
Some sources may rate-limit requests

Add more free sources (VirusTotal, URLScan, etc.)
Implement DNS resolution
Add source selection options
Save scan history
Dark mode support
Subdomain filtering/sorting options

This project is inspired by ProjectDiscovery's Subfinder. Use responsibly and ethically.

This tool is for educational and authorized security testing purposes only. Always obtain proper authorization before scanning any domain you don't own.