diff --git a/dom/plugins/base/npapi.h b/dom/plugins/base/npapi.h
index 1b256163c184..798ee20aad6b 100644
--- a/dom/plugins/base/npapi.h
+++ b/dom/plugins/base/npapi.h
@@ -412,6 +412,8 @@ typedef enum {
 
   NPNVdocumentOrigin = 22,
 
+  NPNVCSSZoomFactor = 23,
+
   NPNVpluginDrawingModel = 1000 /* Get the current drawing model (NPDrawingModel) */
 #if defined(XP_MACOSX)
   , NPNVcontentsScaleFactor = 1001
diff --git a/dom/plugins/base/nsNPAPIPlugin.cpp b/dom/plugins/base/nsNPAPIPlugin.cpp
index 8eff00273d77..a25731178bbd 100644
--- a/dom/plugins/base/nsNPAPIPlugin.cpp
+++ b/dom/plugins/base/nsNPAPIPlugin.cpp
@@ -2031,6 +2031,14 @@ _getvalue(NPP npp, NPNVariable variable, void *result)
   }
 #endif
 
+  case NPNVCSSZoomFactor: {
+    nsNPAPIPluginInstance *inst =
+      (nsNPAPIPluginInstance *) (npp ? npp->ndata : nullptr);
+    double scaleFactor = inst ? inst->GetCSSZoomFactor() : 1.0;
+    *(double*)result = scaleFactor;
+    return NPERR_NO_ERROR;
+  }
+
 #ifdef MOZ_WIDGET_ANDROID
     case kLogInterfaceV0_ANPGetValue: {
       LOG("get log interface");
diff --git a/dom/plugins/base/nsNPAPIPluginInstance.cpp b/dom/plugins/base/nsNPAPIPluginInstance.cpp
index 9aec762ce270..33945ad1e1ce 100644
--- a/dom/plugins/base/nsNPAPIPluginInstance.cpp
+++ b/dom/plugins/base/nsNPAPIPluginInstance.cpp
@@ -1001,7 +1001,8 @@ nsresult nsNPAPIPluginInstance::IsRemoteDrawingCoreAnimation(bool* aDrawing)
 #endif
 }
 
-nsresult nsNPAPIPluginInstance::ContentsScaleFactorChanged(double aContentsScaleFactor)
+nsresult
+nsNPAPIPluginInstance::ContentsScaleFactorChanged(double aContentsScaleFactor)
 {
 #ifdef XP_MACOSX
   if (!mPlugin)
@@ -1021,6 +1022,31 @@ nsresult nsNPAPIPluginInstance::ContentsScaleFactorChanged(double aContentsScale
 #endif
 }
 
+nsresult
+nsNPAPIPluginInstance::CSSZoomFactorChanged(float aCSSZoomFactor)
+{
+  if (RUNNING != mRunning)
+    return NS_OK;
+
+  PLUGIN_LOG(PLUGIN_LOG_NORMAL, ("nsNPAPIPluginInstance informing plugin of CSS Zoom Factor change this=%p\n",this));
+
+  if (!mPlugin || !mPlugin->GetLibrary())
+    return NS_ERROR_FAILURE;
+
+  NPPluginFuncs* pluginFunctions = mPlugin->PluginFuncs();
+
+  if (!pluginFunctions->setvalue)
+    return NS_ERROR_FAILURE;
+
+  PluginDestructionGuard guard(this);
+
+  NPError error;
+  double value = static_cast<double>(aCSSZoomFactor);
+  NS_TRY_SAFE_CALL_RETURN(error, (*pluginFunctions->setvalue)(&mNPP, NPNVCSSZoomFactor, &value), this,
+                          NS_PLUGIN_CALL_UNSAFE_TO_REENTER_GECKO);
+  return (error == NPERR_NO_ERROR) ? NS_OK : NS_ERROR_FAILURE;
+}
+
 nsresult
 nsNPAPIPluginInstance::GetJSObject(JSContext *cx, JSObject** outObject)
 {
@@ -1739,6 +1765,16 @@ nsNPAPIPluginInstance::GetContentsScaleFactor()
   return scaleFactor;
 }
 
+float
+nsNPAPIPluginInstance::GetCSSZoomFactor()
+{
+  float zoomFactor = 1.0;
+  if (mOwner) {
+    mOwner->GetCSSZoomFactor(&zoomFactor);
+  }
+  return zoomFactor;
+}
+
 nsresult
 nsNPAPIPluginInstance::GetRunID(uint32_t* aRunID)
 {
diff --git a/dom/plugins/base/nsNPAPIPluginInstance.h b/dom/plugins/base/nsNPAPIPluginInstance.h
index 7aed6051bb2d..8e26a547ea4e 100644
--- a/dom/plugins/base/nsNPAPIPluginInstance.h
+++ b/dom/plugins/base/nsNPAPIPluginInstance.h
@@ -100,6 +100,7 @@ public:
   nsresult GetDrawingModel(int32_t* aModel);
   nsresult IsRemoteDrawingCoreAnimation(bool* aDrawing);
   nsresult ContentsScaleFactorChanged(double aContentsScaleFactor);
+  nsresult CSSZoomFactorChanged(float aCSSZoomFactor);
   nsresult GetJSObject(JSContext *cx, JSObject** outObject);
   bool ShouldCache();
   nsresult IsWindowless(bool* isWindowless);
@@ -306,6 +307,9 @@ public:
   // Returns the contents scale factor of the screen the plugin is drawn on.
   double GetContentsScaleFactor();
 
+  // Returns the css zoom factor of the document the plugin is drawn on.
+  float GetCSSZoomFactor();
+
   nsresult GetRunID(uint32_t *aRunID);
 
   static bool InPluginCallUnsafeForReentry() { return gInUnsafePluginCalls > 0; }
diff --git a/dom/plugins/base/nsPluginInstanceOwner.cpp b/dom/plugins/base/nsPluginInstanceOwner.cpp
index d449ecc79eb7..7dc2175a1b82 100644
--- a/dom/plugins/base/nsPluginInstanceOwner.cpp
+++ b/dom/plugins/base/nsPluginInstanceOwner.cpp
@@ -361,6 +361,7 @@ nsPluginInstanceOwner::nsPluginInstanceOwner()
   mLastScaleFactor = 1.0;
   mShouldBlurOnActivate = false;
 #endif
+  mLastCSSZoomFactor = 1.0;
   mContentFocused = false;
   mWidgetVisible = true;
   mPluginWindowVisible = false;
@@ -3535,17 +3536,6 @@ nsPluginInstanceOwner::SendWindowFocusChanged(bool aIsActive)
                          NS_PLUGIN_CALL_SAFE_TO_REENTER_GECKO);
 }
 
-void
-nsPluginInstanceOwner::ResolutionMayHaveChanged()
-{
-  double scaleFactor = 1.0;
-  GetContentsScaleFactor(&scaleFactor);
-  if (scaleFactor != mLastScaleFactor) {
-    ContentsScaleFactorChanged(scaleFactor);
-    mLastScaleFactor = scaleFactor;
-   }
-}
-
 void
 nsPluginInstanceOwner::HidePluginWindow()
 {
@@ -3616,6 +3606,28 @@ nsPluginInstanceOwner::UpdateWindowVisibility(bool aVisible)
 }
 #endif // XP_MACOSX
 
+void
+nsPluginInstanceOwner::ResolutionMayHaveChanged()
+{
+#ifdef XP_MACOSX
+  double scaleFactor = 1.0;
+  GetContentsScaleFactor(&scaleFactor);
+  if (scaleFactor != mLastScaleFactor) {
+    ContentsScaleFactorChanged(scaleFactor);
+    mLastScaleFactor = scaleFactor;
+  }
+#endif
+  float zoomFactor = 1.0;
+  GetCSSZoomFactor(&zoomFactor);
+  if (zoomFactor != mLastCSSZoomFactor) {
+    if (mInstance) {
+      mInstance->CSSZoomFactorChanged(zoomFactor);
+    }
+    mLastCSSZoomFactor = zoomFactor;
+  }
+
+}
+
 void
 nsPluginInstanceOwner::UpdateDocumentActiveState(bool aIsActive)
 {
@@ -3695,6 +3707,18 @@ nsPluginInstanceOwner::GetContentsScaleFactor(double *result)
   return NS_OK;
 }
 
+void
+nsPluginInstanceOwner::GetCSSZoomFactor(float *result)
+{
+  nsCOMPtr<nsIContent> content = do_QueryReferent(mContent);
+  nsIPresShell* presShell = nsContentUtils::FindPresShellForDocument(content->OwnerDoc());
+  if (presShell) {
+    *result = presShell->GetPresContext()->DeviceContext()->GetFullZoom();
+  } else {
+    *result = 1.0;
+  }
+}
+
 void nsPluginInstanceOwner::SetFrame(nsPluginFrame *aFrame)
 {
   // Don't do anything if the frame situation hasn't changed.
diff --git a/dom/plugins/base/nsPluginInstanceOwner.h b/dom/plugins/base/nsPluginInstanceOwner.h
index 7fafa09de5be..1b8d9c8ca43b 100644
--- a/dom/plugins/base/nsPluginInstanceOwner.h
+++ b/dom/plugins/base/nsPluginInstanceOwner.h
@@ -138,7 +138,6 @@ public:
   enum { ePluginPaintEnable, ePluginPaintDisable };
 
   void WindowFocusMayHaveChanged();
-  void ResolutionMayHaveChanged();
 
   bool WindowIsActive();
   void SendWindowFocusChanged(bool aIsActive);
@@ -160,6 +159,7 @@ public:
   void UpdateWindowVisibility(bool aVisible);
 #endif // XP_MACOSX
 
+  void ResolutionMayHaveChanged();
   void UpdateDocumentActiveState(bool aIsActive);
 
   void SetFrame(nsPluginFrame *aFrame);
@@ -278,6 +278,7 @@ public:
            const mozilla::widget::CandidateWindowPosition& aPosition);
   bool RequestCommitOrCancel(bool aCommitted);
 
+  void GetCSSZoomFactor(float *result);
 private:
   virtual ~nsPluginInstanceOwner();
 
@@ -328,7 +329,7 @@ private:
   // True if, the next time the window is activated, we should blur ourselves.
   bool                                      mShouldBlurOnActivate;
 #endif
-
+  double                                    mLastCSSZoomFactor;
   // Initially, the event loop nesting level we were created on, it's updated
   // if we detect the appshell is on a lower level as long as we're not stopped.
   // We delay DoStopPlugin() until the appshell reaches this level or lower.
diff --git a/dom/plugins/ipc/PPluginInstance.ipdl b/dom/plugins/ipc/PPluginInstance.ipdl
index ff09c7f8822e..a5381f58fbbe 100644
--- a/dom/plugins/ipc/PPluginInstance.ipdl
+++ b/dom/plugins/ipc/PPluginInstance.ipdl
@@ -97,6 +97,8 @@ child:
   intr NPP_GetValue_NPPVpluginNativeAccessibleAtkPlugId()
     returns (nsCString plug_id, NPError result);
 
+  intr NPP_SetValue_NPNVCSSZoomFactor(double value) returns (NPError result);
+
   intr NPP_SetValue_NPNVmuteAudioBool(bool muted) returns (NPError result);
 
   intr NPP_HandleEvent(NPRemoteEvent event)
diff --git a/dom/plugins/ipc/PluginInstanceChild.cpp b/dom/plugins/ipc/PluginInstanceChild.cpp
index 27b66340402c..63a74fee74cb 100644
--- a/dom/plugins/ipc/PluginInstanceChild.cpp
+++ b/dom/plugins/ipc/PluginInstanceChild.cpp
@@ -543,6 +543,10 @@ PluginInstanceChild::NPN_GetValue(NPNVariable aVar,
     }
 #endif /* XP_MACOSX */
 
+    case NPNVCSSZoomFactor: {
+        *static_cast<double*>(aValue) = mCSSZoomFactor;
+        return NPERR_NO_ERROR;
+    }
 #ifdef DEBUG
     case NPNVjavascriptEnabledBool:
     case NPNVasdEnabledBool:
@@ -817,6 +821,21 @@ PluginInstanceChild::AnswerNPP_SetValue_NPNVprivateModeBool(const bool& value,
     return true;
 }
 
+bool
+PluginInstanceChild::AnswerNPP_SetValue_NPNVCSSZoomFactor(const double& value,
+                                                          NPError* result)
+{
+    if (!mPluginIface->setvalue) {
+        *result = NPERR_GENERIC_ERROR;
+        return true;
+    }
+
+    mCSSZoomFactor = value;
+    double v = value;
+    *result = mPluginIface->setvalue(GetNPP(), NPNVCSSZoomFactor, &v);
+    return true;
+}
+
 bool
 PluginInstanceChild::AnswerNPP_SetValue_NPNVmuteAudioBool(const bool& value,
                                                           NPError* result)
diff --git a/dom/plugins/ipc/PluginInstanceChild.h b/dom/plugins/ipc/PluginInstanceChild.h
index 6ddd751219d7..d04954439ec3 100644
--- a/dom/plugins/ipc/PluginInstanceChild.h
+++ b/dom/plugins/ipc/PluginInstanceChild.h
@@ -89,6 +89,8 @@ protected:
     AnswerNPP_SetValue_NPNVprivateModeBool(const bool& value, NPError* result) override;
     virtual bool
     AnswerNPP_SetValue_NPNVmuteAudioBool(const bool& value, NPError* result) override;
+    virtual bool
+    AnswerNPP_SetValue_NPNVCSSZoomFactor(const double& value, NPError* result) override;
 
     virtual bool
     AnswerNPP_HandleEvent(const NPRemoteEvent& event, int16_t* handled) override;
@@ -403,6 +405,7 @@ private:
 #if defined(XP_DARWIN)
     double mContentsScaleFactor;
 #endif
+    double mCSSZoomFactor;
     int16_t               mDrawingModel;
 
     NPAsyncSurface* mCurrentDirectSurface;
diff --git a/dom/plugins/ipc/PluginInstanceParent.cpp b/dom/plugins/ipc/PluginInstanceParent.cpp
index f4ea848541c2..8bbd952c8277 100644
--- a/dom/plugins/ipc/PluginInstanceParent.cpp
+++ b/dom/plugins/ipc/PluginInstanceParent.cpp
@@ -1735,6 +1735,13 @@ PluginInstanceParent::NPP_SetValue(NPNVariable variable, void* value)
 
         return result;
 
+    case NPNVCSSZoomFactor:
+        if (!CallNPP_SetValue_NPNVCSSZoomFactor(*static_cast<double*>(value),
+                                                &result))
+            return NPERR_GENERIC_ERROR;
+
+        return result;
+
     default:
         NS_ERROR("Unhandled NPNVariable in NPP_SetValue");
         MOZ_LOG(GetPluginLog(), LogLevel::Warning,
diff --git a/layout/generic/nsPluginFrame.cpp b/layout/generic/nsPluginFrame.cpp
index f536a6367e7c..8ed1ab65dbb1 100644
--- a/layout/generic/nsPluginFrame.cpp
+++ b/layout/generic/nsPluginFrame.cpp
@@ -1218,8 +1218,9 @@ nsPluginFrame::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
 #endif
 
   if (aBuilder->IsForPainting() && mInstanceOwner) {
-#ifdef XP_MACOSX
+    // Update plugin frame for both content scaling and full zoom changes.
     mInstanceOwner->ResolutionMayHaveChanged();
+#ifdef XP_MACOSX
     mInstanceOwner->WindowFocusMayHaveChanged();
 #endif
     if (mInstanceOwner->UseAsyncRendering()) {