diff --git a/mobile/android/base/GeckoEvent.java b/mobile/android/base/GeckoEvent.java
index 9105ac30b26..e8de7251a8d 100644
--- a/mobile/android/base/GeckoEvent.java
+++ b/mobile/android/base/GeckoEvent.java
@@ -97,9 +97,6 @@ public class GeckoEvent {
         LOW_MEMORY(35),
         NETWORK_LINK_CHANGE(36),
         TELEMETRY_HISTOGRAM_ADD(37),
-        PREFERENCES_OBSERVE(39),
-        PREFERENCES_GET(40),
-        PREFERENCES_REMOVE_OBSERVERS(41),
         TELEMETRY_UI_SESSION_START(42),
         TELEMETRY_UI_SESSION_STOP(43),
         TELEMETRY_UI_EVENT(44),
@@ -225,8 +222,6 @@ public class GeckoEvent {
     private float mGamepadButtonValue;
     private float[] mGamepadValues;
 
-    private String[] mPrefNames;
-
     private Object mObject;
 
     private GeckoEvent(NativeGeckoEvent event) {
@@ -767,29 +762,6 @@ public class GeckoEvent {
         return event;
     }
 
-    @RobocopTarget
-    public static GeckoEvent createPreferencesObserveEvent(int requestId, String[] prefNames) {
-        GeckoEvent event = GeckoEvent.get(NativeGeckoEvent.PREFERENCES_OBSERVE);
-        event.mCount = requestId;
-        event.mPrefNames = prefNames;
-        return event;
-    }
-
-    @RobocopTarget
-    public static GeckoEvent createPreferencesGetEvent(int requestId, String[] prefNames) {
-        GeckoEvent event = GeckoEvent.get(NativeGeckoEvent.PREFERENCES_GET);
-        event.mCount = requestId;
-        event.mPrefNames = prefNames;
-        return event;
-    }
-
-    @RobocopTarget
-    public static GeckoEvent createPreferencesRemoveObserversEvent(int requestId) {
-        GeckoEvent event = GeckoEvent.get(NativeGeckoEvent.PREFERENCES_REMOVE_OBSERVERS);
-        event.mCount = requestId;
-        return event;
-    }
-
     public static GeckoEvent createLowMemoryEvent(int level) {
         GeckoEvent event = GeckoEvent.get(NativeGeckoEvent.LOW_MEMORY);
         event.mMetaState = level;
diff --git a/widget/android/AndroidJavaWrappers.cpp b/widget/android/AndroidJavaWrappers.cpp
index 7e61af07610..91b07d54b55 100644
--- a/widget/android/AndroidJavaWrappers.cpp
+++ b/widget/android/AndroidJavaWrappers.cpp
@@ -70,7 +70,6 @@ jfieldID AndroidGeckoEvent::jGamepadButtonField = 0;
 jfieldID AndroidGeckoEvent::jGamepadButtonPressedField = 0;
 jfieldID AndroidGeckoEvent::jGamepadButtonValueField = 0;
 jfieldID AndroidGeckoEvent::jGamepadValuesField = 0;
-jfieldID AndroidGeckoEvent::jPrefNamesField = 0;
 jfieldID AndroidGeckoEvent::jObjectField = 0;
 
 jclass AndroidPoint::jPointClass = 0;
@@ -179,7 +178,6 @@ AndroidGeckoEvent::InitGeckoEventClass(JNIEnv *jEnv)
     jGamepadButtonPressedField = geckoEvent.getField("mGamepadButtonPressed", "Z");
     jGamepadButtonValueField = geckoEvent.getField("mGamepadButtonValue", "F");
     jGamepadValuesField = geckoEvent.getField("mGamepadValues", "[F");
-    jPrefNamesField = geckoEvent.getField("mPrefNames", "[Ljava/lang/String;");
     jObjectField = geckoEvent.getField("mObject", "Ljava/lang/Object;");
 }
 
@@ -609,18 +607,6 @@ AndroidGeckoEvent::Init(JNIEnv *jenv, jobject jobj)
             break;
         }
 
-        case PREFERENCES_OBSERVE:
-        case PREFERENCES_GET: {
-            ReadStringArray(mPrefNames, jenv, jPrefNamesField);
-            mCount = jenv->GetIntField(jobj, jCountField);
-            break;
-        }
-
-        case PREFERENCES_REMOVE_OBSERVERS: {
-            mCount = jenv->GetIntField(jobj, jCountField);
-            break;
-        }
-
         default:
             break;
     }
diff --git a/widget/android/AndroidJavaWrappers.h b/widget/android/AndroidJavaWrappers.h
index e94ee830a85..a84f6a27e24 100644
--- a/widget/android/AndroidJavaWrappers.h
+++ b/widget/android/AndroidJavaWrappers.h
@@ -524,7 +524,6 @@ public:
     const nsTArray<int>& ToolTypes() { return mToolTypes; }
     const nsTArray<float>& Orientations() { return mOrientations; }
     const nsTArray<nsIntPoint>& PointRadii() { return mPointRadii; }
-    const nsTArray<nsString>& PrefNames() { return mPrefNames; }
     double X() { return mX; }
     double Y() { return mY; }
     double Z() { return mZ; }
@@ -621,7 +620,6 @@ protected:
     float mGamepadButtonValue;
     nsTArray<float> mGamepadValues;
     nsCOMPtr<nsIObserver> mObserver;
-    nsTArray<nsString> mPrefNames;
     MultiTouchInput mApzInput;
     mozilla::layers::ScrollableLayerGuid mApzGuid;
     uint64_t mApzInputBlockId;
@@ -691,7 +689,6 @@ protected:
     static jfieldID jRangeBackColorField;
     static jfieldID jRangeLineColorField;
     static jfieldID jLocationField;
-    static jfieldID jPrefNamesField;
 
     static jfieldID jConnectionTypeField;
     static jfieldID jIsWifiField;
@@ -745,9 +742,6 @@ public:
         NETWORK_LINK_CHANGE = 36,
         TELEMETRY_HISTOGRAM_ADD = 37,
         ADD_OBSERVER = 38,
-        PREFERENCES_OBSERVE = 39,
-        PREFERENCES_GET = 40,
-        PREFERENCES_REMOVE_OBSERVERS = 41,
         TELEMETRY_UI_SESSION_START = 42,
         TELEMETRY_UI_SESSION_STOP = 43,
         TELEMETRY_UI_EVENT = 44,
diff --git a/widget/android/nsAppShell.cpp b/widget/android/nsAppShell.cpp
index ae1f9f883fd..0e5dfa7fcf5 100644
--- a/widget/android/nsAppShell.cpp
+++ b/widget/android/nsAppShell.cpp
@@ -717,27 +717,6 @@ nsAppShell::LegacyGeckoEvent::Run()
         nsAppShell::gAppShell->AddObserver(curEvent->Characters(), curEvent->Observer());
         break;
 
-    case AndroidGeckoEvent::PREFERENCES_GET:
-    case AndroidGeckoEvent::PREFERENCES_OBSERVE: {
-        const nsTArray<nsString> &prefNames = curEvent->PrefNames();
-        size_t count = prefNames.Length();
-        nsAutoArrayPtr<const char16_t*> prefNamePtrs(new const char16_t*[count]);
-        for (size_t i = 0; i < count; ++i) {
-            prefNamePtrs[i] = prefNames[i].get();
-        }
-
-        if (curEvent->Type() == AndroidGeckoEvent::PREFERENCES_GET) {
-            nsAppShell::gAppShell->mBrowserApp->GetPreferences(curEvent->RequestId(), prefNamePtrs, count);
-        } else {
-            nsAppShell::gAppShell->mBrowserApp->ObservePreferences(curEvent->RequestId(), prefNamePtrs, count);
-        }
-        break;
-    }
-
-    case AndroidGeckoEvent::PREFERENCES_REMOVE_OBSERVERS:
-        nsAppShell::gAppShell->mBrowserApp->RemovePreferenceObservers(curEvent->RequestId());
-        break;
-
     case AndroidGeckoEvent::LOW_MEMORY:
         // TODO hook in memory-reduction stuff for different levels here
         if (curEvent->MetaState() >= AndroidGeckoEvent::MEMORY_PRESSURE_MEDIUM) {