diff --git a/dom/webidl/CaretStateChangedEvent.webidl b/dom/webidl/CaretStateChangedEvent.webidl
index 5fdb9f34b3cb..0a661fe73733 100644
--- a/dom/webidl/CaretStateChangedEvent.webidl
+++ b/dom/webidl/CaretStateChangedEvent.webidl
@@ -11,7 +11,8 @@ enum CaretChangedReason {
   "taponcaret",
   "presscaret",
   "releasecaret",
-  "scroll"
+  "scroll",
+  "dragcaret"
 };
 
 dictionary CaretStateChangedEventInit : EventInit {
@@ -23,6 +24,8 @@ dictionary CaretStateChangedEventInit : EventInit {
   boolean selectionVisible = false;
   boolean selectionEditable = false;
   DOMString selectedTextContent = "";
+  long clientX = 0;
+  long clientY = 0;
 };
 
 [ChromeOnly,
@@ -40,4 +43,8 @@ interface CaretStateChangedEvent : Event {
   readonly attribute boolean selectionVisible;
   readonly attribute boolean selectionEditable;
   readonly attribute DOMString selectedTextContent;
+  [Pref="layout.accessiblecaret.magnifier.enabled"]
+  readonly attribute long clientX;
+  [Pref="layout.accessiblecaret.magnifier.enabled"]
+  readonly attribute long clientY;
 };
diff --git a/layout/base/AccessibleCaretManager.cpp b/layout/base/AccessibleCaretManager.cpp
index 918ee8e518c3..0d1875333a44 100644
--- a/layout/base/AccessibleCaretManager.cpp
+++ b/layout/base/AccessibleCaretManager.cpp
@@ -497,7 +497,7 @@ nsresult AccessibleCaretManager::PressCaret(const nsPoint& aPoint,
     mOffsetYToCaretLogicalPosition =
         mActiveCaret->LogicalPosition().y - aPoint.y;
     SetSelectionDragState(true);
-    DispatchCaretStateChangedEvent(CaretChangedReason::Presscaret);
+    DispatchCaretStateChangedEvent(CaretChangedReason::Presscaret, &aPoint);
     rv = NS_OK;
   }
 
@@ -518,6 +518,10 @@ nsresult AccessibleCaretManager::DragCaret(const nsPoint& aPoint) {
   // We want to scroll the page even if we failed to drag the caret.
   StartSelectionAutoScrollTimer(aPoint);
   UpdateCarets();
+
+  if (StaticPrefs::layout_accessiblecaret_magnifier_enabled()) {
+    DispatchCaretStateChangedEvent(CaretChangedReason::Dragcaret, &aPoint);
+  }
   return NS_OK;
 }
 
@@ -537,7 +541,7 @@ nsresult AccessibleCaretManager::TapCaret(const nsPoint& aPoint) {
   nsresult rv = NS_ERROR_FAILURE;
 
   if (GetCaretMode() == CaretMode::Cursor) {
-    DispatchCaretStateChangedEvent(CaretChangedReason::Taponcaret);
+    DispatchCaretStateChangedEvent(CaretChangedReason::Taponcaret, &aPoint);
     rv = NS_OK;
   }
 
@@ -1427,7 +1431,7 @@ void AccessibleCaretManager::StopSelectionAutoScrollTimer() const {
 }
 
 void AccessibleCaretManager::DispatchCaretStateChangedEvent(
-    CaretChangedReason aReason) {
+    CaretChangedReason aReason, const nsPoint* aPoint) {
   if (MaybeFlushLayout() == Terminated::Yes) {
     return;
   }
@@ -1488,6 +1492,12 @@ void AccessibleCaretManager::DispatchCaretStateChangedEvent(
   init.mCaretVisuallyVisible = mCarets.HasVisuallyVisibleCaret();
   init.mSelectedTextContent = StringifiedSelection();
 
+  if (aPoint) {
+    CSSIntPoint pt = CSSPixel::FromAppUnitsRounded(*aPoint);
+    init.mClientX = pt.x;
+    init.mClientY = pt.y;
+  }
+
   RefPtr<CaretStateChangedEvent> event = CaretStateChangedEvent::Constructor(
       doc, u"mozcaretstatechanged"_ns, init);
 
diff --git a/layout/base/AccessibleCaretManager.h b/layout/base/AccessibleCaretManager.h
index 049c4a44be63..909aeb883895 100644
--- a/layout/base/AccessibleCaretManager.h
+++ b/layout/base/AccessibleCaretManager.h
@@ -304,8 +304,11 @@ class AccessibleCaretManager {
 
   // This function will flush layout, so caller must ensure the PresShell is
   // still valid after calling this method.
+  // @param aPoint The event point when the user is pressing or dragging a
+  //               caret, which is relative to the root frame.
   MOZ_CAN_RUN_SCRIPT
-  virtual void DispatchCaretStateChangedEvent(dom::CaretChangedReason aReason);
+  virtual void DispatchCaretStateChangedEvent(dom::CaretChangedReason aReason,
+                                              const nsPoint* aPoint = nullptr);
 
   // ---------------------------------------------------------------------------
   // Member variables
diff --git a/layout/base/gtest/TestAccessibleCaretManager.cpp b/layout/base/gtest/TestAccessibleCaretManager.cpp
index d23558a18294..464ad68fb043 100644
--- a/layout/base/gtest/TestAccessibleCaretManager.cpp
+++ b/layout/base/gtest/TestAccessibleCaretManager.cpp
@@ -105,8 +105,8 @@ class AccessibleCaretManagerTester : public ::testing::Test {
     Terminated MaybeFlushLayout() override { return Terminated::No; }
 
     MOCK_CONST_METHOD0(GetCaretMode, CaretMode());
-    MOCK_METHOD1(DispatchCaretStateChangedEvent,
-                 void(CaretChangedReason aReason));
+    MOCK_METHOD2(DispatchCaretStateChangedEvent,
+                 void(CaretChangedReason aReason, const nsPoint* aPoint));
     MOCK_CONST_METHOD1(HasNonEmptyTextContent, bool(nsINode* aNode));
 
   };  // class MockAccessibleCaretManager
@@ -148,7 +148,7 @@ MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION {
       .WillRepeatedly(Return(CaretMode::Selection));
 
   EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                            CaretChangedReason::Updateposition))
+                            CaretChangedReason::Updateposition, nullptr))
       .Times(3);
 
   mManager.UpdateCarets();
@@ -176,33 +176,33 @@ MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION {
     InSequence dummy;
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition))
+                              CaretChangedReason::Updateposition, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("update"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Visibilitychange))
+                              CaretChangedReason::Visibilitychange, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("mouse down"));
 
-    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(_)).Times(0);
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(_, nullptr)).Times(0);
     EXPECT_CALL(check, Call("reflow"));
 
-    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(_)).Times(0);
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(_, nullptr)).Times(0);
     EXPECT_CALL(check, Call("blur"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition))
+                              CaretChangedReason::Updateposition, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("mouse up"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition))
+                              CaretChangedReason::Updateposition, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("reflow2"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition))
+                              CaretChangedReason::Updateposition, nullptr))
         .Times(1);
   }
 
@@ -256,33 +256,33 @@ MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION {
     InSequence dummy;
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition))
+                              CaretChangedReason::Updateposition, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("update"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Visibilitychange))
+                              CaretChangedReason::Visibilitychange, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("mouse down"));
 
-    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(_)).Times(0);
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(_, nullptr)).Times(0);
     EXPECT_CALL(check, Call("reflow"));
 
-    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(_)).Times(0);
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(_, nullptr)).Times(0);
     EXPECT_CALL(check, Call("blur"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition))
+                              CaretChangedReason::Updateposition, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("mouse up"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition))
+                              CaretChangedReason::Updateposition, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("reflow2"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition))
+                              CaretChangedReason::Updateposition, nullptr))
         .Times(1);
   }
 
@@ -330,18 +330,18 @@ MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION {
     InSequence dummy;
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition))
+                              CaretChangedReason::Updateposition, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("update"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Visibilitychange))
+                              CaretChangedReason::Visibilitychange, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("keyboard"));
 
     // No CaretStateChanged events should be dispatched since the caret has
     // being hidden in cursor mode.
-    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(_)).Times(0);
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(_, nullptr)).Times(0);
   }
 
   // Simulate typing the end of the input.
@@ -378,15 +378,15 @@ MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION {
         .WillOnce(Return(PositionChangedResult::Invisible));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("updatecarets"));
 
-    EXPECT_CALL(mManager,
-                DispatchCaretStateChangedEvent(CaretChangedReason::Scroll));
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
+                              CaretChangedReason::Scroll, nullptr));
     EXPECT_CALL(check, Call("scrollstart1"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("reflow1"));
 
     // After scroll ended, first caret is visible and second caret is out of
@@ -395,20 +395,20 @@ MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION {
         .WillOnce(Return(PositionChangedResult::Invisible));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("scrollend1"));
 
-    EXPECT_CALL(mManager,
-                DispatchCaretStateChangedEvent(CaretChangedReason::Scroll));
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
+                              CaretChangedReason::Scroll, nullptr));
     EXPECT_CALL(check, Call("scrollstart2"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("reflow2"));
 
     // After the scroll ended, both carets are visible.
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("scrollend2"));
   }
 
@@ -466,18 +466,18 @@ MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION {
         .WillOnce(Return(PositionChangedResult::Invisible));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("updatecarets"));
 
-    EXPECT_CALL(mManager,
-                DispatchCaretStateChangedEvent(CaretChangedReason::Scroll));
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
+                              CaretChangedReason::Scroll, nullptr));
     EXPECT_CALL(check, Call("scrollstart1"));
 
-    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(_)).Times(0);
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(_, nullptr)).Times(0);
     EXPECT_CALL(check, Call("scrollPositionChanged1"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("reflow1"));
 
     // After scroll ended, first caret is visible and second caret is out of
@@ -486,23 +486,23 @@ MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION {
         .WillOnce(Return(PositionChangedResult::Invisible));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("scrollend1"));
 
-    EXPECT_CALL(mManager,
-                DispatchCaretStateChangedEvent(CaretChangedReason::Scroll));
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
+                              CaretChangedReason::Scroll, nullptr));
     EXPECT_CALL(check, Call("scrollstart2"));
 
-    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(_)).Times(0);
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(_, nullptr)).Times(0);
     EXPECT_CALL(check, Call("scrollPositionChanged2"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("reflow2"));
 
     // After the scroll ended, both carets are visible.
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("scrollend2"));
   }
 
@@ -564,12 +564,12 @@ MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION {
     InSequence dummy;
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition))
+                              CaretChangedReason::Updateposition, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("updatecarets"));
 
-    EXPECT_CALL(mManager,
-                DispatchCaretStateChangedEvent(CaretChangedReason::Scroll))
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
+                              CaretChangedReason::Scroll, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("scrollstart1"));
 
@@ -577,12 +577,12 @@ MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION {
     EXPECT_CALL(mManager.FirstCaret(), SetPosition(_, _))
         .WillRepeatedly(Return(PositionChangedResult::Invisible));
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition))
+                              CaretChangedReason::Updateposition, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("scrollend1"));
 
-    EXPECT_CALL(mManager,
-                DispatchCaretStateChangedEvent(CaretChangedReason::Scroll))
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
+                              CaretChangedReason::Scroll, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("scrollstart2"));
 
@@ -590,7 +590,7 @@ MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION {
     EXPECT_CALL(mManager.FirstCaret(), SetPosition(_, _))
         .WillRepeatedly(Return(PositionChangedResult::Position));
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition))
+                              CaretChangedReason::Updateposition, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("scrollend2"));
   }
@@ -628,12 +628,12 @@ MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION {
     InSequence dummy;
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition))
+                              CaretChangedReason::Updateposition, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("updatecarets"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Visibilitychange))
+                              CaretChangedReason::Visibilitychange, nullptr))
         .Times(1);
     EXPECT_CALL(check, Call("hidecarets"));
 
@@ -689,33 +689,33 @@ MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION {
     InSequence dummy;
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("updatecarets"));
 
-    EXPECT_CALL(mManager,
-                DispatchCaretStateChangedEvent(CaretChangedReason::Scroll));
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
+                              CaretChangedReason::Scroll, nullptr));
     EXPECT_CALL(check, Call("scrollstart1"));
 
     EXPECT_CALL(mManager.FirstCaret(), SetPosition(_, _))
         .WillOnce(Return(PositionChangedResult::Invisible));
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("scrollend1"));
 
-    EXPECT_CALL(mManager,
-                DispatchCaretStateChangedEvent(CaretChangedReason::Scroll));
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
+                              CaretChangedReason::Scroll, nullptr));
     EXPECT_CALL(check, Call("scrollstart2"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("scrollend2"));
 
-    EXPECT_CALL(mManager,
-                DispatchCaretStateChangedEvent(CaretChangedReason::Scroll));
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
+                              CaretChangedReason::Scroll, nullptr));
     EXPECT_CALL(check, Call("scrollstart3"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("scrollend3"));
   }
 
@@ -770,37 +770,37 @@ MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION {
     InSequence dummy;
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("singletap updatecarets"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("longtap updatecarets"));
 
-    EXPECT_CALL(mManager,
-                DispatchCaretStateChangedEvent(CaretChangedReason::Scroll));
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
+                              CaretChangedReason::Scroll, nullptr));
     EXPECT_CALL(check, Call("longtap scrollstart1"));
 
     EXPECT_CALL(mManager.FirstCaret(), SetPosition(_, _))
         .WillOnce(Return(PositionChangedResult::Invisible));
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("longtap scrollend1"));
 
-    EXPECT_CALL(mManager,
-                DispatchCaretStateChangedEvent(CaretChangedReason::Scroll));
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
+                              CaretChangedReason::Scroll, nullptr));
     EXPECT_CALL(check, Call("longtap scrollstart2"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("longtap scrollend2"));
 
-    EXPECT_CALL(mManager,
-                DispatchCaretStateChangedEvent(CaretChangedReason::Scroll));
+    EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
+                              CaretChangedReason::Scroll, nullptr));
     EXPECT_CALL(check, Call("longtap scrollstart3"));
 
     EXPECT_CALL(mManager, DispatchCaretStateChangedEvent(
-                              CaretChangedReason::Updateposition));
+                              CaretChangedReason::Updateposition, nullptr));
     EXPECT_CALL(check, Call("longtap scrollend3"));
   }
 
diff --git a/layout/base/tests/accessiblecaret_magnifier.html b/layout/base/tests/accessiblecaret_magnifier.html
new file mode 100644
index 000000000000..855a027725a6
--- /dev/null
+++ b/layout/base/tests/accessiblecaret_magnifier.html
@@ -0,0 +1,91 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+</head>
+<body>
+<p id="display">
+  <div id="editable" contenteditable style="width: 400px; font-size: 4em;">foobarbaz</div>
+</p>
+<script>
+const SimpleTest = parent.SimpleTest;
+const is = parent.is;
+const info = parent.info;
+const isnot = parent.isnot;
+const ok = parent.ok;
+
+window.addEventListener("load", runTest);
+
+async function runTest() {
+  let target = document.getElementById("editable");
+  target.focus();
+  let targetRect = target.getBoundingClientRect();
+  let selection = window.getSelection();
+
+  // Select word then show accessible caret
+  synthesizeTouchAtCenter(target, { type: "touchstart" });
+  synthesizeMouseAtCenter(target, { type: "mouselongtap" });
+  synthesizeTouchAtCenter(target, { type: "touchend" });
+  ok(!selection.getRangeAt(0).collapsed, "Select word");
+
+  let rangeRect = selection.getRangeAt(0).getBoundingClientRect();
+  let presscaret = 0;
+  let dragcaret = 0;
+  let releasecaret = 0;
+
+  const dragStart = {
+    x: Math.round(rangeRect.left),
+    y: Math.round(rangeRect.bottom + 12)
+  };
+  const dragEnd = {
+    x: Math.round(rangeRect.left + 60),
+    y: Math.round(rangeRect.bottom + 12)
+  };
+  let handler;
+
+  let promise = new Promise(resolve => {
+    handler = function(e) {
+      info("mozcaretstatechanged is fired with " + e.reason);
+      switch (e.reason) {
+        case "presscaret":
+          is(dragStart.x, e.clientX, "dragcaret event has clientX data.");
+          is(dragStart.y, e.clientY, "dragcaret event has clientY data.");
+          presscaret++;
+          break;
+        case "dragcaret":
+          is(dragEnd.x, e.clientX, "dragcaret event has clientX data.");
+          is(dragEnd.y, e.clientY, "dragcaret event has clientY data.");
+          dragcaret++;
+          break;
+        case "releasecaret":
+          releasecaret++;
+          resolve();
+          break;
+      }
+    };
+  });
+
+  SpecialPowers.addChromeEventListener("mozcaretstatechanged", handler, true);
+
+  // Drag accessible caret
+  synthesizeTouchAtPoint(dragStart.x, dragStart.y, { type: "touchstart" });
+  synthesizeTouchAtPoint(dragEnd.x, dragEnd.y, { type: "touchmove" });
+  synthesizeTouchAtPoint(dragEnd.x, dragEnd.y, { type: "touchend" });
+
+  await promise;
+
+  SpecialPowers.removeChromeEventListener("mozcaretstatechanged", handler, true);
+
+  is(presscaret, 1, "presscaret is fired correctly");
+  is(dragcaret, 1, "presscaret is fired correctly");
+  is(releasecaret, 1, "releasecaret is fired correctly");
+
+  let newRangeRect = selection.getRangeAt(0).getBoundingClientRect();
+  isnot(rangeRect.left, newRangeRect.left,
+        "Selected range is changed by dragging accessible caret");
+
+  SimpleTest.finish();
+}
+</script>
+</body>
+</html>
diff --git a/layout/base/tests/mochitest.ini b/layout/base/tests/mochitest.ini
index 6845928bc1c2..4e9c4882bcf3 100644
--- a/layout/base/tests/mochitest.ini
+++ b/layout/base/tests/mochitest.ini
@@ -8,6 +8,8 @@ support-files =
   selection-utils.js
   !/gfx/layers/apz/test/mochitest/apz_test_utils.js
 
+[test_accessiblecaret_magnifier.html]
+support-files = accessiblecaret_magnifier.html
 [test_after_paint_pref.html]
 [test_border_radius_hit_testing.html]
 support-files = border_radius_hit_testing_iframe.html
diff --git a/layout/base/tests/test_accessiblecaret_magnifier.html b/layout/base/tests/test_accessiblecaret_magnifier.html
new file mode 100644
index 000000000000..2ac97cccc504
--- /dev/null
+++ b/layout/base/tests/test_accessiblecaret_magnifier.html
@@ -0,0 +1,33 @@
+<!DOCTYPE html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1639087
+-->
+<head>
+  <title>Test for magnifier event</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+  <meta name="viewport" content="width=device-width,minimum-scale=1,initial-scale=1">
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1639087">Mozilla Bug 1639087</a>
+<p id="display">
+  <div id="container" style="width: 600px; height: 500px;"></div>
+</p>
+<script>
+SimpleTest.waitForExplicitFinish();
+SpecialPowers.pushPrefEnv({
+  "set": [
+    ["layout.accessiblecaret.enabled", true],
+    ["layout.accessiblecaret.magnifier.enabled", true]
+  ]
+}, () => {
+  let iframe = document.createElement("iframe");
+  iframe.src = "accessiblecaret_magnifier.html";
+  iframe.style.width = "100%";
+  iframe.style.height = "100%";
+  document.getElementById('container').appendChild(iframe);
+});
+</script>
+</body>
+</html>
diff --git a/modules/libpref/init/StaticPrefList.yaml b/modules/libpref/init/StaticPrefList.yaml
index ae1e683a32e8..4ba1bda0dff8 100644
--- a/modules/libpref/init/StaticPrefList.yaml
+++ b/modules/libpref/init/StaticPrefList.yaml
@@ -7221,6 +7221,13 @@
   value: false
   mirror: always
 
+# To support magnify glass, whether we dispatch additional chrome event such as
+# dragcaret.
+- name: layout.accessiblecaret.magnifier.enabled
+  type: bool
+  value: @IS_ANDROID@
+  mirror: always
+
 # One of several prefs affecting the maximum area to pre-render when animating
 # a large element on the compositor.
 # This pref enables transform (and transform like properties) animations on a