diff --git a/uhabits-android/build.gradle.kts b/uhabits-android/build.gradle.kts
index f4ee9b9cf..8e7103475 100644
--- a/uhabits-android/build.gradle.kts
+++ b/uhabits-android/build.gradle.kts
@@ -32,13 +32,13 @@ tasks.compileLint {
 
 android {
 
-    compileSdk = 30
+    compileSdk = 31
 
     defaultConfig {
         versionCode = 20003
         versionName = "2.0.3"
         minSdk = 23
-        targetSdk = 30
+        targetSdk = 31
         applicationId = "org.isoron.uhabits"
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
     }
diff --git a/uhabits-android/src/main/AndroidManifest.xml b/uhabits-android/src/main/AndroidManifest.xml
index b5d06f181..3b0851207 100644
--- a/uhabits-android/src/main/AndroidManifest.xml
+++ b/uhabits-android/src/main/AndroidManifest.xml
@@ -17,9 +17,10 @@
   ~ with this program. If not, see <http://www.gnu.org/licenses/>.
   -->
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:tools="http://schemas.android.com/tools"
     package="org.isoron.uhabits">
 
+    <uses-permission android:name="android.permission.BROADCAST_CLOSE_SYSTEM_DIALOGS" />
+    <uses-permission android:name="android.permission.SCHEDULE_EXACT_ALARM" />
     <uses-permission android:name="android.permission.VIBRATE" />
     <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
 
@@ -48,11 +49,11 @@
             android:name=".activities.habits.list.ListHabitsActivity"
             android:exported="true"
             android:label="@string/main_activity_title"
-            android:launchMode="singleTop">
-        </activity>
+            android:launchMode="singleTop" />
 
         <activity-alias
             android:name=".MainActivity"
+            android:exported="true"
             android:label="@string/main_activity_title"
             android:launchMode="singleTop"
             android:targetActivity=".activities.habits.list.ListHabitsActivity">
@@ -85,6 +86,7 @@
 
         <activity
             android:name=".widgets.activities.HabitPickerDialog"
+            android:exported="true"
             android:theme="@style/Theme.AppCompat.Light.Dialog">
             <intent-filter>
                 <action android:name="android.appwidget.action.APPWIDGET_CONFIGURE" />
@@ -93,6 +95,7 @@
 
         <activity
             android:name=".widgets.activities.BooleanHabitPickerDialog"
+            android:exported="true"
             android:theme="@style/Theme.AppCompat.Light.Dialog">
             <intent-filter>
                 <action android:name="android.appwidget.action.APPWIDGET_CONFIGURE" />
@@ -101,6 +104,7 @@
 
         <activity
             android:name=".widgets.activities.NumericalHabitPickerDialog"
+            android:exported="true"
             android:theme="@style/Theme.AppCompat.Light.Dialog">
             <intent-filter>
                 <action android:name="android.appwidget.action.APPWIDGET_CONFIGURE" />
@@ -117,9 +121,10 @@
 
         <activity
             android:name=".widgets.activities.NumericalCheckmarkWidgetActivity"
+            android:excludeFromRecents="true"
+            android:exported="true"
             android:label="NumericalCheckmarkWidget"
             android:noHistory="true"
-            android:excludeFromRecents="true"
             android:theme="@style/Theme.AppCompat.Light.Dialog">
             <intent-filter>
                 <action android:name="org.isoron.uhabits.ACTION_SHOW_NUMERICAL_VALUE_ACTIVITY" />
@@ -128,13 +133,14 @@
 
         <activity
             android:name=".notifications.SnoozeDelayPickerActivity"
-            android:taskAffinity=""
             android:excludeFromRecents="true"
             android:launchMode="singleInstance"
+            android:taskAffinity=""
             android:theme="@android:style/Theme.Translucent.NoTitleBar" />
 
         <receiver
             android:name=".widgets.CheckmarkWidgetProvider"
+            android:exported="true"
             android:label="@string/checkmark">
             <intent-filter>
                 <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
@@ -152,6 +158,7 @@
 
         <receiver
             android:name=".widgets.HistoryWidgetProvider"
+            android:exported="true"
             android:label="@string/history">
             <intent-filter>
                 <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
@@ -164,6 +171,7 @@
 
         <receiver
             android:name=".widgets.ScoreWidgetProvider"
+            android:exported="true"
             android:label="@string/score">
             <intent-filter>
                 <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
@@ -176,6 +184,7 @@
 
         <receiver
             android:name=".widgets.StreakWidgetProvider"
+            android:exported="true"
             android:label="@string/streaks">
             <intent-filter>
                 <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
@@ -188,6 +197,7 @@
 
         <receiver
             android:name=".widgets.FrequencyWidgetProvider"
+            android:exported="true"
             android:label="@string/frequency">
             <intent-filter>
                 <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
@@ -200,6 +210,7 @@
 
         <receiver
             android:name=".widgets.TargetWidgetProvider"
+            android:exported="true"
             android:label="@string/target">
             <intent-filter>
                 <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
@@ -210,13 +221,17 @@
                 android:resource="@xml/widget_target_info" />
         </receiver>
 
-        <receiver android:name=".receivers.ReminderReceiver">
+        <receiver
+            android:name=".receivers.ReminderReceiver"
+            android:exported="true">
             <intent-filter>
                 <action android:name="android.intent.action.BOOT_COMPLETED" />
             </intent-filter>
         </receiver>
 
-        <receiver android:name=".receivers.WidgetReceiver">
+        <receiver android:name=".receivers.WidgetReceiver"
+            android:exported="true"
+            android:permission="false">
             <intent-filter>
                 <category android:name="android.intent.category.DEFAULT" />
                 <action android:name="org.isoron.uhabits.ACTION_SET_NUMERICAL_VALUE" />
@@ -267,7 +282,7 @@
         <!-- Locale/Tasker -->
         <receiver
             android:name=".automation.FireSettingReceiver"
-            android:exported="true">
+            android:exported="false">
             <intent-filter>
                 <action android:name="com.twofortyfouram.locale.intent.action.FIRE_SETTING" />
             </intent-filter>
diff --git a/uhabits-android/src/main/java/org/isoron/uhabits/intents/IntentScheduler.kt b/uhabits-android/src/main/java/org/isoron/uhabits/intents/IntentScheduler.kt
index 5a4c79f1d..089af4af2 100644
--- a/uhabits-android/src/main/java/org/isoron/uhabits/intents/IntentScheduler.kt
+++ b/uhabits-android/src/main/java/org/isoron/uhabits/intents/IntentScheduler.kt
@@ -25,8 +25,6 @@ import android.app.AlarmManager.RTC_WAKEUP
 import android.app.PendingIntent
 import android.content.Context
 import android.content.Context.ALARM_SERVICE
-import android.os.Build.VERSION.SDK_INT
-import android.os.Build.VERSION_CODES.M
 import android.util.Log
 import org.isoron.uhabits.core.AppScope
 import org.isoron.uhabits.core.models.Habit
@@ -58,10 +56,7 @@ class IntentScheduler
             )
             return SchedulerResult.IGNORED
         }
-        if (SDK_INT >= M)
-            manager.setExactAndAllowWhileIdle(alarmType, timestamp, intent)
-        else
-            manager.setExact(alarmType, timestamp, intent)
+        manager.setExactAndAllowWhileIdle(alarmType, timestamp, intent)
         return SchedulerResult.OK
     }
 
diff --git a/uhabits-android/src/main/java/org/isoron/uhabits/intents/PendingIntentFactory.kt b/uhabits-android/src/main/java/org/isoron/uhabits/intents/PendingIntentFactory.kt
index 5df329a95..841fa55e6 100644
--- a/uhabits-android/src/main/java/org/isoron/uhabits/intents/PendingIntentFactory.kt
+++ b/uhabits-android/src/main/java/org/isoron/uhabits/intents/PendingIntentFactory.kt
@@ -20,6 +20,7 @@
 package org.isoron.uhabits.intents
 
 import android.app.PendingIntent
+import android.app.PendingIntent.FLAG_IMMUTABLE
 import android.app.PendingIntent.FLAG_UPDATE_CURRENT
 import android.app.PendingIntent.getBroadcast
 import android.content.Context
@@ -49,7 +50,7 @@ class PendingIntentFactory
                 action = WidgetReceiver.ACTION_ADD_REPETITION
                 if (timestamp != null) putExtra("timestamp", timestamp.unixTime)
             },
-            FLAG_UPDATE_CURRENT
+            FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT
         )
 
     fun dismissNotification(habit: Habit): PendingIntent =
@@ -60,7 +61,7 @@ class PendingIntentFactory
                 action = WidgetReceiver.ACTION_DISMISS_REMINDER
                 data = Uri.parse(habit.uriString)
             },
-            FLAG_UPDATE_CURRENT
+            FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT
         )
 
     fun removeRepetition(habit: Habit, timestamp: Timestamp?): PendingIntent =
@@ -72,7 +73,7 @@ class PendingIntentFactory
                 data = Uri.parse(habit.uriString)
                 if (timestamp != null) putExtra("timestamp", timestamp.unixTime)
             },
-            FLAG_UPDATE_CURRENT
+            FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT
         )
 
     fun showHabit(habit: Habit): PendingIntent =
@@ -84,7 +85,7 @@ class PendingIntentFactory
                     habit
                 )
             )
-            .getPendingIntent(0, FLAG_UPDATE_CURRENT)!!
+            .getPendingIntent(0, FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT)!!
 
     fun showReminder(
         habit: Habit,
@@ -100,7 +101,7 @@ class PendingIntentFactory
                 putExtra("timestamp", timestamp)
                 putExtra("reminderTime", reminderTime)
             },
-            FLAG_UPDATE_CURRENT
+            FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT
         )
 
     fun snoozeNotification(habit: Habit): PendingIntent =
@@ -111,7 +112,7 @@ class PendingIntentFactory
                 data = Uri.parse(habit.uriString)
                 action = ReminderReceiver.ACTION_SNOOZE_REMINDER
             },
-            FLAG_UPDATE_CURRENT
+            FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT
         )
 
     fun toggleCheckmark(habit: Habit, timestamp: Long?): PendingIntent =
@@ -123,7 +124,7 @@ class PendingIntentFactory
                 action = WidgetReceiver.ACTION_TOGGLE_REPETITION
                 if (timestamp != null) putExtra("timestamp", timestamp)
             },
-            FLAG_UPDATE_CURRENT
+            FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT
         )
 
     fun setNumericalValue(
@@ -142,7 +143,7 @@ class PendingIntentFactory
                 putExtra("numericalValue", numericalValue)
                 if (timestamp != null) putExtra("timestamp", timestamp)
             },
-            FLAG_UPDATE_CURRENT
+            FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT
         )
 
     fun updateWidgets(): PendingIntent =
@@ -152,6 +153,6 @@ class PendingIntentFactory
             Intent(context, WidgetReceiver::class.java).apply {
                 action = WidgetReceiver.ACTION_UPDATE_WIDGETS_VALUE
             },
-            FLAG_UPDATE_CURRENT
+            FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT
         )
 }
diff --git a/uhabits-android/src/main/java/org/isoron/uhabits/notifications/AndroidNotificationTray.kt b/uhabits-android/src/main/java/org/isoron/uhabits/notifications/AndroidNotificationTray.kt
index 04f3d8d92..3721f04d5 100644
--- a/uhabits-android/src/main/java/org/isoron/uhabits/notifications/AndroidNotificationTray.kt
+++ b/uhabits-android/src/main/java/org/isoron/uhabits/notifications/AndroidNotificationTray.kt
@@ -153,13 +153,15 @@ class AndroidNotificationTray
         if (preferences.shouldMakeNotificationsLed())
             builder.setLights(Color.RED, 1000, 1000)
 
-        val snoozeAction = Action(
-            R.drawable.ic_action_snooze,
-            context.getString(R.string.snooze),
-            pendingIntents.snoozeNotification(habit)
-        )
-        wearableExtender.addAction(snoozeAction)
-        builder.addAction(snoozeAction)
+        if (SDK_INT < Build.VERSION_CODES.S) {
+            val snoozeAction = Action(
+                R.drawable.ic_action_snooze,
+                context.getString(R.string.snooze),
+                pendingIntents.snoozeNotification(habit)
+            )
+            wearableExtender.addAction(snoozeAction)
+            builder.addAction(snoozeAction)
+        }
 
         builder.extend(wearableExtender)
         return builder.build()
diff --git a/uhabits-android/src/main/java/org/isoron/uhabits/receivers/ReminderReceiver.kt b/uhabits-android/src/main/java/org/isoron/uhabits/receivers/ReminderReceiver.kt
index 951b46ae8..6eb10dc7e 100644
--- a/uhabits-android/src/main/java/org/isoron/uhabits/receivers/ReminderReceiver.kt
+++ b/uhabits-android/src/main/java/org/isoron/uhabits/receivers/ReminderReceiver.kt
@@ -22,6 +22,8 @@ import android.content.BroadcastReceiver
 import android.content.ContentUris
 import android.content.Context
 import android.content.Intent
+import android.os.Build
+import android.os.Build.VERSION.SDK_INT
 import android.util.Log
 import org.isoron.uhabits.HabitsApplication
 import org.isoron.uhabits.core.models.Habit
@@ -76,8 +78,21 @@ class ReminderReceiver : BroadcastReceiver() {
                 }
                 ACTION_SNOOZE_REMINDER -> {
                     if (habit == null) return
-                    Log.d("ReminderReceiver", String.format("onSnoozePressed habit=%d", habit.id))
-                    reminderController.onSnoozePressed(habit, context)
+                    if (SDK_INT < Build.VERSION_CODES.S) {
+                        Log.d(
+                            "ReminderReceiver",
+                            String.format("onSnoozePressed habit=%d", habit.id)
+                        )
+                        reminderController.onSnoozePressed(habit, context)
+                    } else {
+                        Log.w(
+                            "ReminderReceiver",
+                            String.format(
+                                "onSnoozePressed habit=%d, should be deactivated in recent versions.",
+                                habit.id
+                            )
+                        )
+                    }
                 }
                 Intent.ACTION_BOOT_COMPLETED -> {
                     Log.d("ReminderReceiver", "onBootCompleted")