diff --git a/mobile/src/main/java/net/activitywatch/android/AWPreferences.kt b/mobile/src/main/java/net/activitywatch/android/AWPreferences.kt
index 227faaed..f4a5c711 100644
--- a/mobile/src/main/java/net/activitywatch/android/AWPreferences.kt
+++ b/mobile/src/main/java/net/activitywatch/android/AWPreferences.kt
@@ -36,4 +36,14 @@ class AWPreferences(context: Context) {
     fun setHostnameMigrated() {
         sharedPreferences.edit().putBoolean("hasMigratedHostname", true).apply()
     }
+
+    // Sync is off by default; user must explicitly enable it once a sync directory
+    // is configured (e.g. via Storage Access Framework).
+    fun isSyncEnabled(): Boolean {
+        return sharedPreferences.getBoolean("syncEnabled", false)
+    }
+
+    fun setSyncEnabled(enabled: Boolean) {
+        sharedPreferences.edit().putBoolean("syncEnabled", enabled).apply()
+    }
 }
diff --git a/mobile/src/main/java/net/activitywatch/android/BackgroundService.kt b/mobile/src/main/java/net/activitywatch/android/BackgroundService.kt
index c0588e7c..df29cee8 100644
--- a/mobile/src/main/java/net/activitywatch/android/BackgroundService.kt
+++ b/mobile/src/main/java/net/activitywatch/android/BackgroundService.kt
@@ -85,8 +85,14 @@ class BackgroundService : Service() {
             }
         }
 
-        // Start the sync scheduler
-        syncScheduler.start()
+        // Start the sync scheduler only when the user has enabled sync.
+        // Default is off — the sync directory is not accessible to other apps
+        // (Android scoped storage), so auto-sync would silently no-op for most users.
+        if (prefs.isSyncEnabled()) {
+            syncScheduler.start()
+        } else {
+            Log.i(TAG, "Sync is disabled (default). Enable it in settings to start syncing.")
+        }
 
         // Schedule event parsing
         scheduleEventParsing()
diff --git a/mobile/src/main/java/net/activitywatch/android/SyncAlarmReceiver.kt b/mobile/src/main/java/net/activitywatch/android/SyncAlarmReceiver.kt
index f74cfbf9..2db62ac1 100644
--- a/mobile/src/main/java/net/activitywatch/android/SyncAlarmReceiver.kt
+++ b/mobile/src/main/java/net/activitywatch/android/SyncAlarmReceiver.kt
@@ -16,6 +16,11 @@ class SyncAlarmReceiver : BroadcastReceiver() {
 
         when (intent.action) {
             "net.activitywatch.android.SYNC_ALARM" -> {
+                if (!AWPreferences(context).isSyncEnabled()) {
+                    Log.i(TAG, "Sync is disabled; cancelling stale alarm")
+                    SyncScheduler.cancelAlarm(context)
+                    return
+                }
                 Log.i(TAG, "Performing scheduled sync...")
                 val pendingResult = goAsync()
                 // Create SyncInterface and perform sync on IO dispatcher to avoid
diff --git a/mobile/src/main/java/net/activitywatch/android/SyncScheduler.kt b/mobile/src/main/java/net/activitywatch/android/SyncScheduler.kt
index d43c6db2..e396203b 100644
--- a/mobile/src/main/java/net/activitywatch/android/SyncScheduler.kt
+++ b/mobile/src/main/java/net/activitywatch/android/SyncScheduler.kt
@@ -105,4 +105,24 @@ class SyncScheduler(private val context: Context) {
             }
         }
     }
+
+    companion object {
+        // Called by SyncAlarmReceiver when sync is disabled, to cancel a stale alarm left
+        // from a previous enable session or an older build that registered it before the pref existed.
+        fun cancelAlarm(context: Context) {
+            val am = context.getSystemService(Context.ALARM_SERVICE) as AlarmManager
+            val intent = Intent(ACTION_SYNC_ALARM).setPackage(context.packageName)
+            val pi = PendingIntent.getBroadcast(
+                context,
+                0,
+                intent,
+                PendingIntent.FLAG_NO_CREATE or PendingIntent.FLAG_IMMUTABLE
+            )
+            if (pi != null) {
+                am.cancel(pi)
+                pi.cancel()
+                Log.i(TAG, "Cancelled stale AlarmManager sync alarm (sync disabled)")
+            }
+        }
+    }
 }