How to fix database/network-error in Firebase

First, confirm your device has internet access. Open a web browser and navigate to https://www.google.com or another website. If you cannot access any websites:

1. Check WiFi or mobile signal strength
2. Try switching networks (WiFi to mobile data or vice versa)
3. Restart your device's network interface
4. Restart your router if on WiFi

If basic connectivity works but Firebase still fails, continue to the next steps.

Verify that Firebase services are not experiencing an outage:

1. Visit https://status.firebase.google.com/

2. Check for any incidents affecting "Realtime Database" in your region
3. If an outage is reported, wait for Google to resolve it
4. If no outage is shown but you still have issues, continue troubleshooting

Occasionally, specific networks (like certain ISPs) may temporarily lose access to Firebase servers.

Add a listener for Firebase connection state and handle errors gracefully:

// Web SDK
const connectedRef = firebase.database().ref(".info/connected");
connectedRef.on("value", (snap) => {
  if (snap.val() === true) {
    console.log("Connected to Firebase");
  } else {
    console.log("Disconnected from Firebase");
  }
});

// Monitor database errors
const db = firebase.database();
db.ref("your/path").on("value", 
  (snapshot) => {
    console.log("Data:", snapshot.val());
  },
  (error) => {
    if (error.code === "NETWORK_ERROR") {
      console.log("Network error, will retry automatically");
    } else {
      console.error("Database error:", error.code, error.message);
    }
  }
);

// Android SDK
val database = FirebaseDatabase.getInstance()
val ref = database.getReference("your/path")

ref.addValueEventListener(object : ValueEventListener {
  override fun onDataChange(snapshot: DataSnapshot) {
    // Handle data
  }
  
  override fun onCancelled(error: DatabaseError) {
    when (error.code) {
      DatabaseError.NETWORK_ERROR -> {
        Log.e("Firebase", "Network error: " + error.message)
        // Implement retry logic with exponential backoff
      }
      else -> Log.e("Firebase", "Database error: " + error.message)
    }
  }
})

Firebase SDKs have built-in automatic retry logic, but you should acknowledge network errors in your UI so users understand what's happening.

Ensure your Firebase Database URL is correctly configured in your app:

// Web SDK
const firebaseConfig = {
  apiKey: "YOUR_API_KEY",
  authDomain: "YOUR_PROJECT.firebaseapp.com",
  databaseURL: "https://YOUR_PROJECT.firebaseio.com", // Make sure this is correct
  projectId: "YOUR_PROJECT",
  // ...
};

const app = initializeApp(firebaseConfig);
const db = getDatabase(app);

// Android - typically configured in google-services.json
// Verify your google-services.json is from the correct Firebase project

1. Go to Firebase Console → Project Settings → Your App
2. Confirm the Database URL matches your Realtime Database instance URL
3. The URL should be in format: https://YOUR_PROJECT.firebaseio.com
4. If incorrect, update your config and redeploy

Network errors can sometimes mask authentication failures:

// Verify user is authenticated
const auth = getAuth();
onAuthStateChanged(auth, (user) => {
  if (user) {
    console.log("Authenticated as:", user.uid);
    // Now safe to access database
  } else {
    console.log("Not authenticated");
  }
});

// Check Realtime Database rules
const db = getDatabase();
const ref = ref(db, "test_read");
get(ref).then((snapshot) => {
  if (snapshot.exists()) {
    console.log("Rules allow read access");
  }
}).catch((error) => {
  console.error(error.code, error.message);
});

1. Go to Firebase Console → Realtime Database → Rules
2. Ensure rules allow your authenticated user to access the paths they're reading/writing
3. During development, you can use: {".read": true, ".write": true} (not for production)
4. If rules deny access, it may show as a network error rather than a permission error

Sometimes cached authentication tokens or connection state become corrupted:

1. iOS: Settings → Apps → Your App → Storage → Clear App Data
2. Android: Settings → Apps → Your App → Storage → Clear Cache / Clear Data
3. Web: Open developer tools → Application → Clear Site Data
4. Restart the app and try again

This forces the SDK to reinitialize and obtain fresh authentication tokens.

To isolate whether the issue is network-specific:

1. If currently on WiFi, switch to mobile data (or vice versa)
2. Try a different WiFi network (coffee shop, library, another location)
3. If using corporate WiFi, try personal network
4. Test from a different device on the same network

If it works on one network but not another, the issue is network/firewall-specific:
- Contact your network administrator if on corporate WiFi
- Request that *.firebaseio.com and related Firebase domains are whitelisted
- Check for VPN conflicts (try disabling temporarily for testing)