diff --git a/mobile/.gitignore b/mobile/.gitignore
index c7d39cbd..7cecd1c9 100644
--- a/mobile/.gitignore
+++ b/mobile/.gitignore
@@ -1,6 +1,7 @@
 /build
 /debug
 /release
+/google/
 
 # tests aren't ready yet
 /src/androidTest
diff --git a/mobile/build.gradle b/mobile/build.gradle
index 8a61afc0..5c88b9c8 100644
--- a/mobile/build.gradle
+++ b/mobile/build.gradle
@@ -11,8 +11,8 @@ android {
         minSdkVersion 21
         targetSdkVersion 28
         resConfigs "zh-rCN"
-        versionCode 25
-        versionName "1.3.4"
+        versionCode 26
+        versionName "1.3.5"
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
     }
     buildTypes {
@@ -26,11 +26,23 @@ android {
         }
     }
     dataBinding.enabled = true
+    flavorDimensions("freedom")
+    productFlavors {
+        freedom {
+            dimension "freedom"
+            buildConfigField "boolean", "DONATIONS", "true"
+        }
+        google {
+            dimension "freedom"
+            buildConfigField "boolean", "DONATIONS", "false"
+        }
+    }
 }
 
 dependencies {
     kapt "androidx.databinding:databinding-compiler:$androidPluginVersion"
     implementation fileTree(dir: 'libs', include: ['*.jar'])
+    implementation 'com.android.billingclient:billing:1.1'
     implementation "com.android.support:customtabs:$supportLibraryVersion"
     implementation "com.android.support:design:$supportLibraryVersion"
     implementation "com.android.support:preference-v14:$supportLibraryVersion"
diff --git a/mobile/src/main/AndroidManifest.xml b/mobile/src/main/AndroidManifest.xml
index 2796e587..2959d482 100644
--- a/mobile/src/main/AndroidManifest.xml
+++ b/mobile/src/main/AndroidManifest.xml
@@ -21,6 +21,7 @@
 
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
     <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
+    <uses-permission android:name="android.permission.BILLING"/>
     <uses-permission android:name="android.permission.BLUETOOTH"/>
     <uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"/>
     <uses-permission android:name="android.permission.CHANGE_WIFI_STATE"/>
diff --git a/mobile/src/main/java/be/mygod/vpnhotspot/EBegFragment.kt b/mobile/src/main/java/be/mygod/vpnhotspot/EBegFragment.kt
new file mode 100644
index 00000000..2f6c7e37
--- /dev/null
+++ b/mobile/src/main/java/be/mygod/vpnhotspot/EBegFragment.kt
@@ -0,0 +1,103 @@
+package be.mygod.vpnhotspot
+
+import android.app.AlertDialog
+import android.net.Uri
+import android.os.Bundle
+import android.support.v4.app.DialogFragment
+import android.util.Log
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.view.ViewStub
+import android.widget.ArrayAdapter
+import android.widget.Button
+import android.widget.Spinner
+import com.android.billingclient.api.*
+import com.crashlytics.android.Crashlytics
+
+/**
+ * Based on: https://github.com/PrivacyApps/donations/blob/747d36a18433c7e9329691054122a8ad337a62d2/Donations/src/main/java/org/sufficientlysecure/donations/DonationsFragment.java
+ */
+class EBegFragment : DialogFragment(), PurchasesUpdatedListener, BillingClientStateListener,
+        SkuDetailsResponseListener, ConsumeResponseListener {
+    companion object {
+        private const val TAG = "EBegFragment"
+    }
+
+    private lateinit var billingClient: BillingClient
+    private lateinit var googleSpinner: Spinner
+    private var skus: MutableList<SkuDetails>? = null
+        set(value) {
+            field = value
+            googleSpinner.apply {
+                val adapter = ArrayAdapter(requireContext(), android.R.layout.simple_spinner_item,
+                        value?.map { it.price } ?: emptyList())
+                adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
+                setAdapter(adapter)
+            }
+        }
+
+    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View =
+            inflater.inflate(R.layout.fragment_ebeg, container, false)
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+        googleSpinner = view.findViewById(R.id.donations__google_android_market_spinner)
+        billingClient = BillingClient.newBuilder(view.context).setListener(this).build()
+        onBillingServiceDisconnected()
+        view.findViewById<Button>(R.id.donations__google_android_market_donate_button).setOnClickListener {
+            val skus = skus
+            if (skus == null) {
+                openDialog(android.R.drawable.ic_dialog_alert,
+                        R.string.donations__google_android_market_not_supported_title,
+                        getString(R.string.donations__google_android_market_not_supported))
+            } else billingClient.launchBillingFlow(requireActivity(), BillingFlowParams.newBuilder()
+                    .setSku(skus[googleSpinner.selectedItemPosition].sku).setType(BillingClient.SkuType.INAPP).build())
+        }
+        @Suppress("ConstantConditionIf")
+        if (BuildConfig.DONATIONS) (view.findViewById<ViewStub>(R.id.donations__more_stub).inflate() as Button)
+                .setOnClickListener {
+                    (activity as MainActivity).launchUrl(Uri.parse("https://mygod.be/donate/"))
+                }
+    }
+
+    private fun openDialog(icon: Int, title: Int, message: String) = AlertDialog.Builder(requireContext()).apply {
+        setIcon(icon)
+        setTitle(title)
+        setMessage(message)
+        isCancelable = true
+        setNeutralButton(R.string.donations__button_close) { dialog, _ -> dialog.dismiss() }
+    }.show()
+
+    override fun onBillingServiceDisconnected() {
+        skus = null
+        billingClient.startConnection(this)
+    }
+    override fun onBillingSetupFinished(responseCode: Int) {
+        if (responseCode == BillingClient.BillingResponse.OK) {
+            billingClient.querySkuDetailsAsync(
+                    SkuDetailsParams.newBuilder().apply {
+                        setSkusList(listOf("donate001", "donate002", "donate005", "donate010", "donate020", "donate050",
+                                "donate100", "donate200", "donatemax"))
+                        setType(BillingClient.SkuType.INAPP)
+                    }.build(), this)
+        } else Crashlytics.log(Log.ERROR, TAG, "onBillingSetupFinished: $responseCode")
+    }
+
+    override fun onSkuDetailsResponse(responseCode: Int, skuDetailsList: MutableList<SkuDetails>?) {
+        if (responseCode == BillingClient.BillingResponse.OK) skus = skuDetailsList
+        else Crashlytics.log(Log.ERROR, TAG, "onSkuDetailsResponse: $responseCode")
+    }
+
+    override fun onPurchasesUpdated(responseCode: Int, purchases: MutableList<Purchase>?) {
+        if (responseCode == BillingClient.BillingResponse.OK && purchases != null) {
+            // directly consume in-app purchase, so that people can donate multiple times
+            purchases.forEach { billingClient.consumeAsync(it.purchaseToken, this) }
+        } else Crashlytics.log(Log.ERROR, TAG, "onPurchasesUpdated: $responseCode")
+    }
+    override fun onConsumeResponse(responseCode: Int, purchaseToken: String?) {
+        if (responseCode == BillingClient.BillingResponse.OK) {
+            openDialog(android.R.drawable.ic_dialog_info, R.string.donations__thanks_dialog_title,
+                    getString(R.string.donations__thanks_dialog))
+        } else Crashlytics.log(Log.ERROR, TAG, "onConsumeResponse: $responseCode")
+    }
+}
diff --git a/mobile/src/main/java/be/mygod/vpnhotspot/MainActivity.kt b/mobile/src/main/java/be/mygod/vpnhotspot/MainActivity.kt
index b327d0e3..dd798de5 100644
--- a/mobile/src/main/java/be/mygod/vpnhotspot/MainActivity.kt
+++ b/mobile/src/main/java/be/mygod/vpnhotspot/MainActivity.kt
@@ -1,10 +1,13 @@
 package be.mygod.vpnhotspot
 
 import android.content.ComponentName
+import android.content.Intent
 import android.content.ServiceConnection
 import android.databinding.DataBindingUtil
+import android.net.Uri
 import android.os.Bundle
 import android.os.IBinder
+import android.support.customtabs.CustomTabsIntent
 import android.support.design.internal.BottomNavigationMenuView
 import android.support.design.widget.BottomNavigationView
 import android.support.v4.app.Fragment
@@ -23,6 +26,12 @@ class MainActivity : AppCompatActivity(), BottomNavigationView.OnNavigationItemS
     private lateinit var binding: ActivityMainBinding
     private lateinit var badge: QBadgeView
     private var clients: ClientMonitorService.Binder? = null
+    private val customTabsIntent by lazy {
+        CustomTabsIntent.Builder()
+                .setToolbarColor(ContextCompat.getColor(this, R.color.colorPrimary))
+                .build()
+    }
+    fun launchUrl(url: Uri) = customTabsIntent.launchUrl(this, url)
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -76,4 +85,9 @@ class MainActivity : AppCompatActivity(), BottomNavigationView.OnNavigationItemS
 
     private fun displayFragment(fragment: Fragment) =
             supportFragmentManager.beginTransaction().replace(R.id.fragmentHolder, fragment).commitAllowingStateLoss()
+
+    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
+        super.onActivityResult(requestCode, resultCode, data)
+        supportFragmentManager.findFragmentByTag("donationsFragment")?.onActivityResult(requestCode, resultCode, data)
+    }
 }
diff --git a/mobile/src/main/java/be/mygod/vpnhotspot/SettingsPreferenceFragment.kt b/mobile/src/main/java/be/mygod/vpnhotspot/SettingsPreferenceFragment.kt
index f0eba762..5349b723 100644
--- a/mobile/src/main/java/be/mygod/vpnhotspot/SettingsPreferenceFragment.kt
+++ b/mobile/src/main/java/be/mygod/vpnhotspot/SettingsPreferenceFragment.kt
@@ -5,8 +5,6 @@ import android.content.Intent
 import android.net.Uri
 import android.os.Build
 import android.os.Bundle
-import android.support.customtabs.CustomTabsIntent
-import android.support.v4.content.ContextCompat
 import android.support.v4.content.FileProvider
 import android.support.v7.preference.Preference
 import android.widget.Toast
@@ -26,12 +24,6 @@ import java.net.NetworkInterface
 import java.net.SocketException
 
 class SettingsPreferenceFragment : PreferenceFragmentCompat() {
-    private val customTabsIntent by lazy {
-        CustomTabsIntent.Builder()
-                .setToolbarColor(ContextCompat.getColor(requireContext(), R.color.colorPrimary))
-                .build()
-    }
-
     override fun onCreatePreferencesFix(savedInstanceState: Bundle?, rootKey: String?) {
         preferenceManager.preferenceDataStore = SharedPreferenceDataStore(app.pref)
         addPreferencesFromResource(R.xml.pref_settings)
@@ -98,7 +90,11 @@ class SettingsPreferenceFragment : PreferenceFragmentCompat() {
             true
         }
         findPreference("misc.source").setOnPreferenceClickListener {
-            customTabsIntent.launchUrl(requireActivity(), Uri.parse("https://github.com/Mygod/VPNHotspot"))
+            (activity as MainActivity).launchUrl(Uri.parse("https://github.com/Mygod/VPNHotspot"))
+            true
+        }
+        findPreference("misc.donate").setOnPreferenceClickListener {
+            EBegFragment().show(fragmentManager, "ebeg_fragment")
             true
         }
     }
diff --git a/mobile/src/main/res/drawable/ic_action_card_giftcard.xml b/mobile/src/main/res/drawable/ic_action_card_giftcard.xml
new file mode 100644
index 00000000..c8f76dfc
--- /dev/null
+++ b/mobile/src/main/res/drawable/ic_action_card_giftcard.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24dp"
+        android:height="24dp"
+        android:viewportWidth="24.0"
+        android:viewportHeight="24.0"
+        android:tint="?attr/colorControlNormal">
+    <path
+        android:fillColor="#FF000000"
+        android:pathData="M20,6h-2.18c0.11,-0.31 0.18,-0.65 0.18,-1 0,-1.66 -1.34,-3 -3,-3 -1.05,0 -1.96,0.54 -2.5,1.35l-0.5,0.67 -0.5,-0.68C10.96,2.54 10.05,2 9,2 7.34,2 6,3.34 6,5c0,0.35 0.07,0.69 0.18,1L4,6c-1.11,0 -1.99,0.89 -1.99,2L2,19c0,1.11 0.89,2 2,2h16c1.11,0 2,-0.89 2,-2L22,8c0,-1.11 -0.89,-2 -2,-2zM15,4c0.55,0 1,0.45 1,1s-0.45,1 -1,1 -1,-0.45 -1,-1 0.45,-1 1,-1zM9,4c0.55,0 1,0.45 1,1s-0.45,1 -1,1 -1,-0.45 -1,-1 0.45,-1 1,-1zM20,19L4,19v-2h16v2zM20,14L4,14L4,8h5.08L7,10.83 8.62,12 11,8.76l1,-1.36 1,1.36L15.38,12 17,10.83 14.92,8L20,8v6z"/>
+</vector>
diff --git a/mobile/src/main/res/layout/fragment_ebeg.xml b/mobile/src/main/res/layout/fragment_ebeg.xml
new file mode 100644
index 00000000..c607f8a5
--- /dev/null
+++ b/mobile/src/main/res/layout/fragment_ebeg.xml
@@ -0,0 +1,69 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Based on:
+  ~ https://github.com/PrivacyApps/donations/blob/747d36a18433c7e9329691054122a8ad337a62d2/Donations/src/main/res/layout/donations__fragment.xml
+  ~ https://github.com/PrivacyApps/donations/blob/747d36a18433c7e9329691054122a8ad337a62d2/Donations/src/main/res/layout/donations__fragment_google.xml
+  ~ -->
+<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
+            android:layout_width="match_parent"
+            android:layout_height="match_parent">
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:isScrollContainer="true"
+        android:orientation="vertical"
+        android:padding="16dp">
+        <TextView
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_gravity="center_vertical"
+            android:text="@string/donations__description"
+            android:textAppearance="@android:style/TextAppearance.Small" />
+        <LinearLayout android:layout_width="match_parent"
+                      android:layout_height="wrap_content"
+                      android:orientation="vertical" >
+
+            <TextView
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:paddingTop="5dp"
+                android:text="@string/donations__google_android_market"
+                android:textAppearance="?android:attr/textAppearanceMedium" />
+
+            <TextView
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:paddingBottom="5dp"
+                android:paddingTop="5dp"
+                android:text="@string/donations__google_android_market_description"
+                android:textAppearance="@android:style/TextAppearance.Small" />
+
+            <LinearLayout
+                android:layout_width="match_parent"
+                android:layout_height="match_parent"
+                android:orientation="horizontal"
+                android:paddingTop="5dp" >
+
+                <Spinner
+                    android:id="@+id/donations__google_android_market_spinner"
+                    android:layout_width="match_parent"
+                    android:layout_height="wrap_content"
+                    android:layout_weight="1"
+                    android:prompt="@string/donations__google_android_market_text" />
+
+                <Button
+                    android:id="@+id/donations__google_android_market_donate_button"
+                    android:layout_width="match_parent"
+                    android:layout_height="wrap_content"
+                    android:layout_weight="1"
+                    android:text="@string/donations__google_android_market_donate_button" />
+            </LinearLayout>
+
+        </LinearLayout>
+        <ViewStub
+            android:id="@+id/donations__more_stub"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout="@layout/fragment_ebeg_more" />
+    </LinearLayout>
+</ScrollView>
diff --git a/mobile/src/main/res/layout/fragment_ebeg_more.xml b/mobile/src/main/res/layout/fragment_ebeg_more.xml
new file mode 100644
index 00000000..a70d5cf6
--- /dev/null
+++ b/mobile/src/main/res/layout/fragment_ebeg_more.xml
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Button xmlns:android="http://schemas.android.com/apk/res/android"
+        android:id="@+id/donations__more_donate_button"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:text="@string/settings_misc_donate_more"/>
diff --git a/mobile/src/main/res/values-zh-rCN/strings.xml b/mobile/src/main/res/values-zh-rCN/strings.xml
index 5bb9d3bc..f3b1fe31 100644
--- a/mobile/src/main/res/values-zh-rCN/strings.xml
+++ b/mobile/src/main/res/values-zh-rCN/strings.xml
@@ -74,6 +74,9 @@
     <string name="settings_misc_logcat_summary">这种非常有用哇</string>
     <string name="settings_misc_source">查看 GitHub 上的源码</string>
     <string name="settings_misc_source_summary">Star, 提交 issues, 合作</string>
+    <string name="settings_misc_donate">捐款</string>
+    <string name="settings_misc_donate_summary">请给我钱</string>
+    <string name="settings_misc_donate_more">PayPal, Flattr 等其他方式…</string>
 
     <string name="notification_tethering_title">VPN 共享已启用</string>
     <string name="notification_channel_tethering">VPN 共享服务</string>
@@ -94,4 +97,17 @@
     <string name="credentials_password_too_short" msgid="7502749986405522663">"密码至少应包含 8 个字符。"</string>
     <string name="wifi_save" msgid="3331121567988522826">"保存"</string>
     <string name="wifi_cancel" msgid="6763568902542968964">"取消"</string>
+
+    <!-- Based on: https://github.com/PrivacyApps/donations/blob/747d36a18433c7e9329691054122a8ad337a62d2/Donations/src/main/res/values-zh/donations__strings.xml -->
+    <string name="donations__button_close">关闭</string>
+    <string name="donations__google_android_market">Google Play 商店</string>
+    <string name="donations__google_android_market_not_supported_title">不支持 In-App 捐赠。</string>
+    <string name="donations__google_android_market_not_supported">不支持 In-App 捐赠。你的 Google Play 商店是否安装正确了呢？</string>
+    <string name="donations__google_android_market_donate_button">捐赠！</string>
+    <string name="donations__google_android_market_text">捐赠多少？</string>
+    <string name="donations__thanks_dialog_title">谢谢！</string>
+    <string name="donations__thanks_dialog">谢谢捐赠！\n非常感谢您！</string>
+
+    <string name="donations__description">觉得此应用很有用？\n捐赠给该开发者以支持此应用的开发！</string>
+    <string name="donations__google_android_market_description">Google 收取 30% 的费用</string>
 </resources>
diff --git a/mobile/src/main/res/values/strings.xml b/mobile/src/main/res/values/strings.xml
index da9eb218..680d3265 100644
--- a/mobile/src/main/res/values/strings.xml
+++ b/mobile/src/main/res/values/strings.xml
@@ -79,6 +79,9 @@
     <string name="settings_misc_logcat_summary">Such useful very wow</string>
     <string name="settings_misc_source">View on GitHub</string>
     <string name="settings_misc_source_summary">Star, submit issues and contribute</string>
+    <string name="settings_misc_donate">Donate</string>
+    <string name="settings_misc_donate_summary">I love money</string>
+    <string name="settings_misc_donate_more">PayPal, Flattr, more…</string>
 
     <string name="notification_tethering_title">VPN tethering active</string>
     <string name="notification_channel_tethering">VPN Tethering Service</string>
@@ -101,4 +104,16 @@
     <string name="credentials_password_too_short">The password must have at least 8 characters.</string>
     <string name="wifi_save">Save</string>
     <string name="wifi_cancel">Cancel</string>
+
+    <!-- Based on: https://github.com/PrivacyApps/donations/blob/747d36a18433c7e9329691054122a8ad337a62d2/Donations/src/main/res/values/donations__strings.xml -->
+    <string name="donations__button_close">Close</string>
+    <string name="donations__description">Do you find this application useful?\nSupport its development by sending a donation to the developer!</string>
+    <string name="donations__google_android_market">Google Play Store</string>
+    <string name="donations__google_android_market_not_supported_title">In-App Donations are not supported.</string>
+    <string name="donations__google_android_market_not_supported">In-App Donations are not supported. Is Google Play Store installed correctly?</string>
+    <string name="donations__google_android_market_description">Google charges a fee of 30%</string>
+    <string name="donations__google_android_market_donate_button">Donate!</string>
+    <string name="donations__google_android_market_text">How much?</string>
+    <string name="donations__thanks_dialog_title">Thanks!</string>
+    <string name="donations__thanks_dialog">Thanks for donating!\nI really appreciate this!</string>
 </resources>
diff --git a/mobile/src/main/res/xml/pref_settings.xml b/mobile/src/main/res/xml/pref_settings.xml
index 034bef5b..a81fcb6d 100644
--- a/mobile/src/main/res/xml/pref_settings.xml
+++ b/mobile/src/main/res/xml/pref_settings.xml
@@ -48,5 +48,10 @@
             android:icon="@drawable/ic_toggle_star"
             android:title="@string/settings_misc_source"
             android:summary="@string/settings_misc_source_summary"/>
+        <Preference
+            android:key="misc.donate"
+            android:icon="@drawable/ic_action_card_giftcard"
+            android:title="@string/settings_misc_donate"
+            android:summary="@string/settings_misc_donate_summary"/>
     </PreferenceCategory>
 </PreferenceScreen>