diff --git a/editor/libeditor/CreateElementTransaction.cpp b/editor/libeditor/CreateElementTransaction.cpp
index 716ecb25244c..0e12b6580265 100644
--- a/editor/libeditor/CreateElementTransaction.cpp
+++ b/editor/libeditor/CreateElementTransaction.cpp
@@ -95,7 +95,7 @@ CreateElementTransaction::DoTransaction()
   NS_ENSURE_STATE(mNewNode);
 
   // Try to insert formatting whitespace for the new node:
-  mEditorBase->MarkNodeDirty(GetAsDOMNode(mNewNode));
+  mEditorBase->MarkNodeDirty(mNewNode);
 
   // Insert the new node
   ErrorResult error;
diff --git a/editor/libeditor/EditorBase.cpp b/editor/libeditor/EditorBase.cpp
index 1677b749f31a..cfcf83148dca 100644
--- a/editor/libeditor/EditorBase.cpp
+++ b/editor/libeditor/EditorBase.cpp
@@ -75,7 +75,6 @@
 #include "nsIContent.h"                 // for nsIContent
 #include "nsIDocument.h"                // for nsIDocument
 #include "nsIDOMEventListener.h"        // for nsIDOMEventListener
-#include "nsIDOMNode.h"                 // for nsIDOMNode, etc.
 #include "nsIDocumentStateListener.h"   // for nsIDocumentStateListener
 #include "nsIEditActionListener.h"      // for nsIEditActionListener
 #include "nsIEditorObserver.h"          // for nsIEditorObserver
@@ -1261,16 +1260,16 @@ EditorBase::RemoveAttributeWithTransaction(Element& aElement,
 }
 
 NS_IMETHODIMP
-EditorBase::MarkNodeDirty(nsIDOMNode* aNode)
+EditorBase::MarkNodeDirty(nsINode* aNode)
 {
   // Mark the node dirty, but not for webpages (bug 599983)
   if (!OutputsMozDirty()) {
     return NS_OK;
   }
-  nsCOMPtr<dom::Element> element = do_QueryInterface(aNode);
-  if (element) {
-    element->SetAttr(kNameSpaceID_None, nsGkAtoms::mozdirty,
-                     EmptyString(), false);
+  if (aNode && aNode->IsElement()) {
+    RefPtr<Element> element = aNode->AsElement();
+    element->SetAttr(kNameSpaceID_None, nsGkAtoms::mozdirty, EmptyString(),
+                     false);
   }
   return NS_OK;
 }
@@ -1404,23 +1403,22 @@ EditorBase::CreateNodeWithTransaction(
 }
 
 NS_IMETHODIMP
-EditorBase::InsertNode(nsIDOMNode* aNodeToInsert,
-                       nsIDOMNode* aContainer,
+EditorBase::InsertNode(nsINode* aNodeToInsert,
+                       nsINode* aContainer,
                        int32_t aOffset)
 {
   nsCOMPtr<nsIContent> contentToInsert = do_QueryInterface(aNodeToInsert);
   if (NS_WARN_IF(!contentToInsert)) {
     return NS_ERROR_NULL_POINTER;
   }
-  nsCOMPtr<nsINode> container = do_QueryInterface(aContainer);
-  if (NS_WARN_IF(!container)) {
+  if (NS_WARN_IF(!aContainer)) {
     return NS_ERROR_NULL_POINTER;
   }
   int32_t offset =
-    aOffset < 0 ? static_cast<int32_t>(container->Length()) :
-                  std::min(aOffset, static_cast<int32_t>(container->Length()));
+    aOffset < 0 ? static_cast<int32_t>(aContainer->Length()) :
+                  std::min(aOffset, static_cast<int32_t>(aContainer->Length()));
   return InsertNodeWithTransaction(*contentToInsert,
-                                   EditorRawDOMPoint(container, offset));
+                                   EditorRawDOMPoint(aContainer, offset));
 }
 
 template<typename PT, typename CT>
@@ -1463,21 +1461,20 @@ EditorBase::InsertNodeWithTransaction(
 }
 
 NS_IMETHODIMP
-EditorBase::SplitNode(nsIDOMNode* aNode,
+EditorBase::SplitNode(nsINode* aNode,
                       int32_t aOffset,
-                      nsIDOMNode** aNewLeftNode)
+                      nsINode** aNewLeftNode)
 {
-  nsCOMPtr<nsIContent> node = do_QueryInterface(aNode);
-  if (NS_WARN_IF(!node)) {
+  if (NS_WARN_IF(!aNode)) {
     return NS_ERROR_INVALID_ARG;
   }
 
   int32_t offset = std::min(std::max(aOffset, 0),
-                            static_cast<int32_t>(node->Length()));
+                            static_cast<int32_t>(aNode->Length()));
   ErrorResult error;
   nsCOMPtr<nsIContent> newNode =
-    SplitNodeWithTransaction(EditorRawDOMPoint(node, offset), error);
-  *aNewLeftNode = GetAsDOMNode(newNode.forget().take());
+    SplitNodeWithTransaction(EditorRawDOMPoint(aNode, offset), error);
+  newNode.forget(aNewLeftNode);
   if (NS_WARN_IF(error.Failed())) {
     return error.StealNSResult();
   }
@@ -1547,14 +1544,12 @@ EditorBase::SplitNodeWithTransaction(
 }
 
 NS_IMETHODIMP
-EditorBase::JoinNodes(nsIDOMNode* aLeftNode,
-                      nsIDOMNode* aRightNode,
-                      nsIDOMNode*)
+EditorBase::JoinNodes(nsINode* aLeftNode,
+                      nsINode* aRightNode,
+                      nsINode*)
 {
-  nsCOMPtr<nsINode> leftNode = do_QueryInterface(aLeftNode);
-  nsCOMPtr<nsINode> rightNode = do_QueryInterface(aRightNode);
-  NS_ENSURE_STATE(leftNode && rightNode && leftNode->GetParentNode());
-  return JoinNodesWithTransaction(*leftNode, *rightNode);
+  NS_ENSURE_STATE(aLeftNode && aRightNode && aLeftNode->GetParentNode());
+  return JoinNodesWithTransaction(*aLeftNode, *aRightNode);
 }
 
 nsresult
@@ -1621,13 +1616,12 @@ EditorBase::JoinNodesWithTransaction(nsINode& aLeftNode,
 }
 
 NS_IMETHODIMP
-EditorBase::DeleteNode(nsIDOMNode* aNode)
+EditorBase::DeleteNode(nsINode* aNode)
 {
-  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
-  if (NS_WARN_IF(!node)) {
+  if (NS_WARN_IF(!aNode)) {
     return NS_ERROR_INVALID_ARG;
   }
-  return DeleteNodeWithTransaction(*node);
+  return DeleteNodeWithTransaction(*aNode);
 }
 
 nsresult
@@ -2443,22 +2437,16 @@ EditorBase::EndOperation()
 
 NS_IMETHODIMP
 EditorBase::CloneAttribute(const nsAString& aAttribute,
-                           nsIDOMNode* aDestNode,
-                           nsIDOMNode* aSourceNode)
+                           Element* aDestElement,
+                           Element* aSourceElement)
 {
-  NS_ENSURE_TRUE(aDestNode && aSourceNode, NS_ERROR_NULL_POINTER);
+  NS_ENSURE_TRUE(aDestElement && aSourceElement, NS_ERROR_NULL_POINTER);
   if (NS_WARN_IF(aAttribute.IsEmpty())) {
     return NS_ERROR_FAILURE;
   }
 
-  nsCOMPtr<Element> destElement = do_QueryInterface(aDestNode);
-  nsCOMPtr<Element> sourceElement = do_QueryInterface(aSourceNode);
-  if (NS_WARN_IF(!destElement) || NS_WARN_IF(!sourceElement)) {
-    return NS_ERROR_INVALID_ARG;
-  }
-
   RefPtr<nsAtom> attribute = NS_Atomize(aAttribute);
-  return CloneAttributeWithTransaction(*attribute, *destElement, *sourceElement);
+  return CloneAttributeWithTransaction(*attribute, *aDestElement, *aSourceElement);
 }
 
 nsresult
@@ -2478,16 +2466,14 @@ EditorBase::CloneAttributeWithTransaction(nsAtom& aAttribute,
  * @param aSource   Must be a DOM element.
  */
 NS_IMETHODIMP
-EditorBase::CloneAttributes(nsIDOMNode* aDestDOMElement,
-                            nsIDOMNode* aSourceDOMElement)
+EditorBase::CloneAttributes(Element* aDestElement,
+                            Element* aSourceElement)
 {
-  nsCOMPtr<Element> destElement = do_QueryInterface(aDestDOMElement);
-  nsCOMPtr<Element> sourceElement = do_QueryInterface(aSourceDOMElement);
-  if (NS_WARN_IF(!destElement) || NS_WARN_IF(!sourceElement)) {
+  if (NS_WARN_IF(!aDestElement) || NS_WARN_IF(!aSourceElement)) {
     return NS_ERROR_INVALID_ARG;
   }
 
-  CloneAttributesWithTransaction(*destElement, *sourceElement);
+  CloneAttributesWithTransaction(*aDestElement, *aSourceElement);
 
   return NS_OK;
 }
@@ -3372,20 +3358,6 @@ EditorBase::DoJoinNodes(nsINode* aNodeToKeep,
   return err.StealNSResult();
 }
 
-// static
-int32_t
-EditorBase::GetChildOffset(nsIDOMNode* aChild,
-                           nsIDOMNode* aParent)
-{
-  MOZ_ASSERT(aChild && aParent);
-
-  nsCOMPtr<nsINode> parent = do_QueryInterface(aParent);
-  nsCOMPtr<nsINode> child = do_QueryInterface(aChild);
-  MOZ_ASSERT(parent && child);
-
-  return GetChildOffset(child, parent);
-}
-
 // static
 int32_t
 EditorBase::GetChildOffset(nsINode* aChild,
@@ -3753,16 +3725,6 @@ EditorBase::TagCanContainTag(nsAtom& aParentTag,
   return true;
 }
 
-bool
-EditorBase::IsRoot(nsIDOMNode* inNode)
-{
-  NS_ENSURE_TRUE(inNode, false);
-
-  nsCOMPtr<nsIDOMNode> rootNode = do_QueryInterface(GetRoot());
-
-  return inNode == rootNode;
-}
-
 bool
 EditorBase::IsRoot(nsINode* inNode)
 {
@@ -3781,13 +3743,6 @@ EditorBase::IsEditorRoot(nsINode* aNode)
   return aNode == rootNode;
 }
 
-bool
-EditorBase::IsDescendantOfRoot(nsIDOMNode* inNode)
-{
-  nsCOMPtr<nsINode> node = do_QueryInterface(inNode);
-  return IsDescendantOfRoot(node);
-}
-
 bool
 EditorBase::IsDescendantOfRoot(nsINode* inNode)
 {
@@ -3814,13 +3769,6 @@ EditorBase::IsContainer(nsINode* aNode)
   return aNode ? true : false;
 }
 
-bool
-EditorBase::IsEditable(nsIDOMNode* aNode)
-{
-  nsCOMPtr<nsIContent> content = do_QueryInterface(aNode);
-  return IsEditable(content);
-}
-
 uint32_t
 EditorBase::CountEditableChildren(nsINode* aNode)
 {
@@ -3873,19 +3821,6 @@ EditorBase::ResetModificationCount()
   return NS_OK;
 }
 
-nsAtom*
-EditorBase::GetTag(nsIDOMNode* aNode)
-{
-  nsCOMPtr<nsIContent> content = do_QueryInterface(aNode);
-
-  if (!content) {
-    NS_ASSERTION(aNode, "null node passed to EditorBase::GetTag()");
-    return nullptr;
-  }
-
-  return content->NodeInfo()->NameAtom();
-}
-
 bool
 EditorBase::AreNodesSameType(nsIContent* aNode1,
                              nsIContent* aNode2)
@@ -3895,18 +3830,6 @@ EditorBase::AreNodesSameType(nsIContent* aNode1,
   return aNode1->NodeInfo()->NameAtom() == aNode2->NodeInfo()->NameAtom();
 }
 
-bool
-EditorBase::IsTextNode(nsIDOMNode* aNode)
-{
-  if (!aNode) {
-    NS_NOTREACHED("null node passed to IsTextNode()");
-    return false;
-  }
-
-  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
-  return IsTextNode(node);
-}
-
 // static
 nsIContent*
 EditorBase::GetNodeAtRangeOffsetPoint(const RawRangeBoundary& aPoint)
diff --git a/editor/libeditor/EditorBase.h b/editor/libeditor/EditorBase.h
index 73c149dd98b6..2b563b72e514 100644
--- a/editor/libeditor/EditorBase.h
+++ b/editor/libeditor/EditorBase.h
@@ -38,7 +38,6 @@
 class mozInlineSpellChecker;
 class nsAtom;
 class nsIContent;
-class nsIDOMNode;
 class nsIDocumentStateListener;
 class nsIEditActionListener;
 class nsIEditorObserver;
@@ -1399,14 +1398,6 @@ protected: // May be called by friends.
   nsIContent* GetLeftmostChild(nsINode *aCurrentNode,
                                bool bNoBlockCrossing = false);
 
-  /**
-   * Returns true if aNode is of the type implied by aTag.
-   */
-  static inline bool NodeIsType(nsIDOMNode* aNode, nsAtom* aTag)
-  {
-    return GetTag(aNode) == aTag;
-  }
-
   /**
    * Returns true if aParent can contain a child of type aTag.
    */
@@ -1418,14 +1409,12 @@ protected: // May be called by friends.
   /**
    * Returns true if aNode is our root node.
    */
-  bool IsRoot(nsIDOMNode* inNode);
   bool IsRoot(nsINode* inNode);
   bool IsEditorRoot(nsINode* aNode);
 
   /**
    * Returns true if aNode is a descendant of our root node.
    */
-  bool IsDescendantOfRoot(nsIDOMNode* inNode);
   bool IsDescendantOfRoot(nsINode* inNode);
   bool IsDescendantOfEditorRoot(nsINode* aNode);
 
@@ -1437,7 +1426,6 @@ protected: // May be called by friends.
   /**
    * returns true if aNode is an editable node.
    */
-  bool IsEditable(nsIDOMNode* aNode);
   bool IsEditable(nsINode* aNode)
   {
     NS_ENSURE_TRUE(aNode, false);
@@ -1503,11 +1491,8 @@ protected: // May be called by friends.
   /**
    * From html rules code - migration in progress.
    */
-  static nsAtom* GetTag(nsIDOMNode* aNode);
-
   virtual bool AreNodesSameType(nsIContent* aNode1, nsIContent* aNode2);
 
-  static bool IsTextNode(nsIDOMNode* aNode);
   static bool IsTextNode(nsINode* aNode)
   {
     return aNode->NodeType() == nsINode::TEXT_NODE;
@@ -1796,8 +1781,6 @@ protected: // Shouldn't be used by friend classes
    *      methods may return wrong index if aChild doesn't have previous
    *      sibling or next sibling.
    */
-  static int32_t GetChildOffset(nsIDOMNode* aChild,
-                                nsIDOMNode* aParent);
   static int32_t GetChildOffset(nsINode* aChild,
                                 nsINode* aParent);
 
diff --git a/editor/libeditor/EditorDOMPoint.h b/editor/libeditor/EditorDOMPoint.h
index aab51636a477..4fe9f1b03ec3 100644
--- a/editor/libeditor/EditorDOMPoint.h
+++ b/editor/libeditor/EditorDOMPoint.h
@@ -16,7 +16,6 @@
 #include "nsCOMPtr.h"
 #include "nsGkAtoms.h"
 #include "nsIContent.h"
-#include "nsIDOMNode.h"
 #include "nsINode.h"
 
 namespace mozilla {
@@ -97,14 +96,6 @@ public:
     }
   }
 
-  EditorDOMPointBase(nsIDOMNode* aDOMContainer,
-                     int32_t aOffset)
-    : mIsChildInitialized(false)
-  {
-    nsCOMPtr<nsINode> container = do_QueryInterface(aDOMContainer);
-    this->Set(container, aOffset);
-  }
-
   /**
    * Different from RangeBoundary, aPointedNode should be a child node
    * which you want to refer.
@@ -123,16 +114,6 @@ public:
       "Initializing RangeBoundary with invalid value");
   }
 
-  explicit EditorDOMPointBase(nsIDOMNode* aDOMPointedNode)
-    : mIsChildInitialized(false)
-  {
-    nsCOMPtr<nsIContent> child = do_QueryInterface(aDOMPointedNode);
-    if (NS_WARN_IF(!child)) {
-      return;
-    }
-    this->Set(child);
-  }
-
   EditorDOMPointBase(nsINode* aContainer,
                      nsIContent* aPointedNode,
                      int32_t aOffset)
@@ -198,12 +179,6 @@ public:
     return mParent ? mParent->GetAsText() : nullptr;
   }
 
-  nsIDOMNode*
-  GetContainerAsDOMNode() const
-  {
-    return mParent ? mParent->AsDOMNode() : nullptr;
-  }
-
   /**
    * CanContainerHaveChildren() returns true if the container node can have
    * child nodes.  Otherwise, e.g., when the container is a text node, returns
diff --git a/editor/libeditor/HTMLEditUtils.cpp b/editor/libeditor/HTMLEditUtils.cpp
index bfbb12f10b15..d790b22d34e8 100644
--- a/editor/libeditor/HTMLEditUtils.cpp
+++ b/editor/libeditor/HTMLEditUtils.cpp
@@ -18,7 +18,6 @@
 #include "nsGkAtoms.h"                  // for nsGkAtoms, nsGkAtoms::a, etc.
 #include "nsHTMLTags.h"
 #include "nsAtom.h"                    // for nsAtom
-#include "nsIDOMNode.h"                 // for nsIDOMNode
 #include "nsNameSpaceManager.h"        // for kNameSpaceID_None
 #include "nsLiteralString.h"            // for NS_LITERAL_STRING
 #include "nsString.h"                   // for nsAutoString
@@ -29,14 +28,6 @@ namespace mozilla {
 /**
  * IsInlineStyle() returns true if aNode is an inline style.
  */
-bool
-HTMLEditUtils::IsInlineStyle(nsIDOMNode* aNode)
-{
-  MOZ_ASSERT(aNode);
-  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
-  return node && IsInlineStyle(node);
-}
-
 bool
 HTMLEditUtils::IsInlineStyle(nsINode* aNode)
 {
@@ -57,14 +48,6 @@ HTMLEditUtils::IsInlineStyle(nsINode* aNode)
 /**
  * IsFormatNode() returns true if aNode is a format node.
  */
-bool
-HTMLEditUtils::IsFormatNode(nsIDOMNode* aNode)
-{
-  MOZ_ASSERT(aNode);
-  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
-  return node && IsFormatNode(node);
-}
-
 bool
 HTMLEditUtils::IsFormatNode(nsINode* aNode)
 {
@@ -111,35 +94,9 @@ HTMLEditUtils::IsHeader(nsINode& aNode)
                                    nsGkAtoms::h6);
 }
 
-bool
-HTMLEditUtils::IsHeader(nsIDOMNode* aNode)
-{
-  MOZ_ASSERT(aNode);
-  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
-  MOZ_ASSERT(node);
-  return IsHeader(*node);
-}
-
-/**
- * IsParagraph() returns true if aNode is an html paragraph.
- */
-bool
-HTMLEditUtils::IsParagraph(nsIDOMNode* aNode)
-{
-  return EditorBase::NodeIsType(aNode, nsGkAtoms::p);
-}
-
 /**
  * IsListItem() returns true if aNode is an html list item.
  */
-bool
-HTMLEditUtils::IsListItem(nsIDOMNode* aNode)
-{
-  MOZ_ASSERT(aNode);
-  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
-  return node && IsListItem(node);
-}
-
 bool
 HTMLEditUtils::IsListItem(nsINode* aNode)
 {
@@ -152,14 +109,6 @@ HTMLEditUtils::IsListItem(nsINode* aNode)
 /**
  * IsTableElement() returns true if aNode is an html table, td, tr, ...
  */
-bool
-HTMLEditUtils::IsTableElement(nsIDOMNode* aNode)
-{
-  MOZ_ASSERT(aNode);
-  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
-  return node && IsTableElement(node);
-}
-
 bool
 HTMLEditUtils::IsTableElement(nsINode* aNode)
 {
@@ -178,14 +127,6 @@ HTMLEditUtils::IsTableElement(nsINode* aNode)
  * IsTableElementButNotTable() returns true if aNode is an html td, tr, ...
  * (doesn't include table)
  */
-bool
-HTMLEditUtils::IsTableElementButNotTable(nsIDOMNode* aNode)
-{
-  MOZ_ASSERT(aNode);
-  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
-  return node && IsTableElementButNotTable(node);
-}
-
 bool
 HTMLEditUtils::IsTableElementButNotTable(nsINode* aNode)
 {
@@ -211,12 +152,6 @@ HTMLEditUtils::IsTable(nsINode* aNode)
 /**
  * IsTableRow() returns true if aNode is an html tr.
  */
-bool
-HTMLEditUtils::IsTableRow(nsIDOMNode* aNode)
-{
-  return EditorBase::NodeIsType(aNode, nsGkAtoms::tr);
-}
-
 bool
 HTMLEditUtils::IsTableRow(nsINode* aNode)
 {
@@ -226,14 +161,6 @@ HTMLEditUtils::IsTableRow(nsINode* aNode)
 /**
  * IsTableCell() returns true if aNode is an html td or th.
  */
-bool
-HTMLEditUtils::IsTableCell(nsIDOMNode* aNode)
-{
-  MOZ_ASSERT(aNode);
-  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
-  return node && IsTableCell(node);
-}
-
 bool
 HTMLEditUtils::IsTableCell(nsINode* aNode)
 {
@@ -254,14 +181,6 @@ HTMLEditUtils::IsTableCellOrCaption(nsINode& aNode)
 /**
  * IsList() returns true if aNode is an html list.
  */
-bool
-HTMLEditUtils::IsList(nsIDOMNode* aNode)
-{
-  MOZ_ASSERT(aNode);
-  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
-  return node && IsList(node);
-}
-
 bool
 HTMLEditUtils::IsList(nsINode* aNode)
 {
@@ -271,43 +190,9 @@ HTMLEditUtils::IsList(nsINode* aNode)
                                     nsGkAtoms::dl);
 }
 
-/**
- * IsOrderedList() returns true if aNode is an html ordered list.
- */
-bool
-HTMLEditUtils::IsOrderedList(nsIDOMNode* aNode)
-{
-  return EditorBase::NodeIsType(aNode, nsGkAtoms::ol);
-}
-
-
-/**
- * IsUnorderedList() returns true if aNode is an html unordered list.
- */
-bool
-HTMLEditUtils::IsUnorderedList(nsIDOMNode* aNode)
-{
-  return EditorBase::NodeIsType(aNode, nsGkAtoms::ul);
-}
-
-/**
- * IsBlockquote() returns true if aNode is an html blockquote node.
- */
-bool
-HTMLEditUtils::IsBlockquote(nsIDOMNode* aNode)
-{
-  return EditorBase::NodeIsType(aNode, nsGkAtoms::blockquote);
-}
-
 /**
  * IsPre() returns true if aNode is an html pre node.
  */
-bool
-HTMLEditUtils::IsPre(nsIDOMNode* aNode)
-{
-  return EditorBase::NodeIsType(aNode, nsGkAtoms::pre);
-}
-
 bool
 HTMLEditUtils::IsPre(nsINode* aNode)
 {
@@ -323,12 +208,6 @@ HTMLEditUtils::IsImage(nsINode* aNode)
   return aNode && aNode->IsHTMLElement(nsGkAtoms::img);
 }
 
-bool
-HTMLEditUtils::IsImage(nsIDOMNode* aNode)
-{
-  return EditorBase::NodeIsType(aNode, nsGkAtoms::img);
-}
-
 bool
 HTMLEditUtils::IsLink(nsINode* aNode)
 {
@@ -361,15 +240,6 @@ HTMLEditUtils::IsNamedAnchor(nsINode* aNode)
                                      text) && !text.IsEmpty();
 }
 
-/**
- * IsDiv() returns true if aNode is an html div node.
- */
-bool
-HTMLEditUtils::IsDiv(nsIDOMNode* aNode)
-{
-  return EditorBase::NodeIsType(aNode, nsGkAtoms::div);
-}
-
 /**
  * IsMozDiv() returns true if aNode is an html div node with |type = _moz|.
  */
@@ -384,14 +254,6 @@ HTMLEditUtils::IsMozDiv(nsINode* aNode)
 /**
  * IsMailCite() returns true if aNode is an html blockquote with |type=cite|.
  */
-bool
-HTMLEditUtils::IsMailCite(nsIDOMNode* aNode)
-{
-  MOZ_ASSERT(aNode);
-  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
-  return node && IsMailCite(node);
-}
-
 bool
 HTMLEditUtils::IsMailCite(nsINode* aNode)
 {
@@ -419,14 +281,6 @@ HTMLEditUtils::IsMailCite(nsINode* aNode)
 /**
  * IsFormWidget() returns true if aNode is a form widget of some kind.
  */
-bool
-HTMLEditUtils::IsFormWidget(nsIDOMNode* aNode)
-{
-  MOZ_ASSERT(aNode);
-  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
-  return node && IsFormWidget(node);
-}
-
 bool
 HTMLEditUtils::IsFormWidget(nsINode* aNode)
 {
diff --git a/editor/libeditor/HTMLEditUtils.h b/editor/libeditor/HTMLEditUtils.h
index 3d512802c0a9..406f8f19a0b8 100644
--- a/editor/libeditor/HTMLEditUtils.h
+++ b/editor/libeditor/HTMLEditUtils.h
@@ -8,7 +8,6 @@
 
 #include <stdint.h>
 
-class nsIDOMNode;
 class nsINode;
 
 namespace mozilla {
@@ -17,43 +16,24 @@ class HTMLEditUtils final
 {
 public:
   static bool IsInlineStyle(nsINode* aNode);
-  static bool IsInlineStyle(nsIDOMNode *aNode);
   static bool IsFormatNode(nsINode* aNode);
-  static bool IsFormatNode(nsIDOMNode* aNode);
   static bool IsNodeThatCanOutdent(nsINode* aNode);
   static bool IsHeader(nsINode& aNode);
-  static bool IsHeader(nsIDOMNode* aNode);
-  static bool IsParagraph(nsIDOMNode* aNode);
   static bool IsListItem(nsINode* aNode);
-  static bool IsListItem(nsIDOMNode* aNode);
   static bool IsTable(nsINode* aNode);
-  static bool IsTableRow(nsIDOMNode* aNode);
   static bool IsTableRow(nsINode* aNode);
   static bool IsTableElement(nsINode* aNode);
-  static bool IsTableElement(nsIDOMNode* aNode);
   static bool IsTableElementButNotTable(nsINode* aNode);
-  static bool IsTableElementButNotTable(nsIDOMNode* aNode);
   static bool IsTableCell(nsINode* node);
-  static bool IsTableCell(nsIDOMNode* aNode);
   static bool IsTableCellOrCaption(nsINode& aNode);
   static bool IsList(nsINode* aNode);
-  static bool IsList(nsIDOMNode* aNode);
-  static bool IsOrderedList(nsIDOMNode* aNode);
-  static bool IsUnorderedList(nsIDOMNode* aNode);
-  static bool IsBlockquote(nsIDOMNode* aNode);
-  static bool IsPre(nsIDOMNode* aNode);
   static bool IsPre(nsINode* aNode);
-  static bool IsAnchor(nsIDOMNode* aNode);
   static bool IsImage(nsINode* aNode);
-  static bool IsImage(nsIDOMNode* aNode);
   static bool IsLink(nsINode* aNode);
   static bool IsNamedAnchor(nsINode* aNode);
-  static bool IsDiv(nsIDOMNode* aNode);
   static bool IsMozDiv(nsINode* aNode);
   static bool IsMailCite(nsINode* aNode);
-  static bool IsMailCite(nsIDOMNode* aNode);
   static bool IsFormWidget(nsINode* aNode);
-  static bool IsFormWidget(nsIDOMNode* aNode);
   static bool SupportsAlignAttr(nsINode& aNode);
   static bool CanContain(int32_t aParent, int32_t aChild);
   static bool IsContainer(int32_t aTag);
diff --git a/editor/libeditor/HTMLEditor.cpp b/editor/libeditor/HTMLEditor.cpp
index 6c919825fadc..bf18357adf21 100644
--- a/editor/libeditor/HTMLEditor.cpp
+++ b/editor/libeditor/HTMLEditor.cpp
@@ -2590,11 +2590,12 @@ HTMLEditor::GetSelectedElement(const nsAString& aTagName,
       iter->Init(currange);
       // loop through the content iterator for each content node
       while (!iter->IsDone()) {
-        // Query interface to cast nsIContent to nsIDOMNode
+        // Query interface to cast nsIContent to Element
         //  then get tagType to compare to  aTagName
         // Clone node of each desired type and append it to the aDomFrag
         nsINode* currentNode = iter->GetCurrentNode();
-        selectedElement = do_QueryInterface(currentNode);
+        selectedElement = currentNode && currentNode->IsElement() ?
+          currentNode->AsElement() : nullptr;
         if (selectedElement) {
           // If we already found a node, then we have another element,
           //  thus there's not just one element selected
@@ -3171,8 +3172,7 @@ HTMLEditor::GetEmbeddedObjects(nsIArray** aNodeList)
                                        nsGkAtoms::a) ||
           (element->IsHTMLElement(nsGkAtoms::body) &&
            element->HasAttr(kNameSpaceID_None, nsGkAtoms::background))) {
-        nsCOMPtr<nsIDOMNode> domNode = do_QueryInterface(node);
-        nodes->AppendElement(domNode);
+        nodes->AppendElement(node);
        }
      }
      iter->Next();
@@ -3259,13 +3259,12 @@ HTMLEditor::DeleteNodeWithTransaction(nsINode& aNode)
 }
 
 NS_IMETHODIMP
-HTMLEditor::DeleteNode(nsIDOMNode* aDOMNode)
+HTMLEditor::DeleteNode(nsINode* aNode)
 {
-  nsCOMPtr<nsINode> node = do_QueryInterface(aDOMNode);
-  if (NS_WARN_IF(!node)) {
+  if (NS_WARN_IF(!aNode)) {
     return NS_ERROR_INVALID_ARG;
   }
-  nsresult rv = DeleteNodeWithTransaction(*node);
+  nsresult rv = DeleteNodeWithTransaction(*aNode);
   if (NS_WARN_IF(NS_FAILED(rv))) {
     return rv;
   }
@@ -3673,18 +3672,6 @@ HTMLEditor::GetEnclosingTable(nsINode* aNode)
   return nullptr;
 }
 
-nsIDOMNode*
-HTMLEditor::GetEnclosingTable(nsIDOMNode* aNode)
-{
-  MOZ_ASSERT(aNode, "null node passed to HTMLEditor::GetEnclosingTable");
-  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
-  NS_ENSURE_TRUE(node, nullptr);
-  nsCOMPtr<Element> table = GetEnclosingTable(node);
-  nsCOMPtr<nsIDOMNode> ret = do_QueryInterface(table);
-  return ret;
-}
-
-
 /**
  * This method scans the selection for adjacent text nodes
  * and collapses them into a single text node.
diff --git a/editor/libeditor/HTMLEditor.h b/editor/libeditor/HTMLEditor.h
index d452aaf27f7e..d3c656052ae4 100644
--- a/editor/libeditor/HTMLEditor.h
+++ b/editor/libeditor/HTMLEditor.h
@@ -141,7 +141,7 @@ public:
 
   NS_IMETHOD PasteTransferable(nsITransferable* aTransferable) override;
 
-  NS_IMETHOD DeleteNode(nsIDOMNode* aNode) override;
+  NS_IMETHOD DeleteNode(nsINode* aNode) override;
 
   NS_IMETHOD SelectAll() override;
 
@@ -1018,7 +1018,6 @@ protected: // Shouldn't be used by friend classes
   nsresult SetSelectionAtDocumentStart(Selection* aSelection);
 
   static Element* GetEnclosingTable(nsINode* aNode);
-  static nsIDOMNode* GetEnclosingTable(nsIDOMNode* aNode);
 
   // Methods for handling plaintext quotations
   nsresult PasteAsPlaintextQuotation(int32_t aSelectionType);
diff --git a/editor/libeditor/HTMLEditorDataTransfer.cpp b/editor/libeditor/HTMLEditorDataTransfer.cpp
index 825e000ecf1a..1aaa175732cd 100644
--- a/editor/libeditor/HTMLEditorDataTransfer.cpp
+++ b/editor/libeditor/HTMLEditorDataTransfer.cpp
@@ -38,7 +38,6 @@
 #include "nsGkAtoms.h"
 #include "nsIClipboard.h"
 #include "nsIContent.h"
-#include "nsIDOMNode.h"
 #include "nsIDocument.h"
 #include "nsIFile.h"
 #include "nsIInputStream.h"
diff --git a/editor/libeditor/HTMLTableEditor.cpp b/editor/libeditor/HTMLTableEditor.cpp
index 23ea0f686b2d..2aa97ae27142 100644
--- a/editor/libeditor/HTMLTableEditor.cpp
+++ b/editor/libeditor/HTMLTableEditor.cpp
@@ -24,7 +24,6 @@
 #include "nsGkAtoms.h"
 #include "nsAtom.h"
 #include "nsIContent.h"
-#include "nsIDOMNode.h"
 #include "nsIFrame.h"
 #include "nsINode.h"
 #include "nsIPresShell.h"
diff --git a/editor/libeditor/InsertNodeTransaction.cpp b/editor/libeditor/InsertNodeTransaction.cpp
index 81885c479a9d..01abbdb3811b 100644
--- a/editor/libeditor/InsertNodeTransaction.cpp
+++ b/editor/libeditor/InsertNodeTransaction.cpp
@@ -102,7 +102,7 @@ InsertNodeTransaction::DoTransaction()
     }
   }
 
-  mEditorBase->MarkNodeDirty(GetAsDOMNode(mContentToInsert));
+  mEditorBase->MarkNodeDirty(mContentToInsert);
 
   ErrorResult error;
   mPointToInsert.GetContainer()->InsertBefore(*mContentToInsert,
diff --git a/editor/libeditor/SplitNodeTransaction.cpp b/editor/libeditor/SplitNodeTransaction.cpp
index dc6bef91d1e2..41bf9cb0a663 100644
--- a/editor/libeditor/SplitNodeTransaction.cpp
+++ b/editor/libeditor/SplitNodeTransaction.cpp
@@ -85,7 +85,7 @@ SplitNodeTransaction::DoTransaction()
     return NS_ERROR_UNEXPECTED;
   }
   mNewLeftNode = dont_AddRef(clone.forget().take()->AsContent());
-  mEditorBase->MarkNodeDirty(mStartOfRightNode.GetContainerAsDOMNode());
+  mEditorBase->MarkNodeDirty(mStartOfRightNode.GetContainer());
 
   // Get the parent node
   mParent = mStartOfRightNode.GetContainer()->GetParentNode();
diff --git a/editor/libeditor/TextEditor.cpp b/editor/libeditor/TextEditor.cpp
index 9530491781bd..c3d9c13b41ca 100644
--- a/editor/libeditor/TextEditor.cpp
+++ b/editor/libeditor/TextEditor.cpp
@@ -41,7 +41,6 @@
 #include "nsIClipboard.h"
 #include "nsIContent.h"
 #include "nsIContentIterator.h"
-#include "nsIDOMNode.h"
 #include "nsIDocumentEncoder.h"
 #include "nsINode.h"
 #include "nsIPresShell.h"
diff --git a/editor/libeditor/tests/test_root_element_replacement.html b/editor/libeditor/tests/test_root_element_replacement.html
index f8b6f4336eb4..e60dd2592836 100644
--- a/editor/libeditor/tests/test_root_element_replacement.html
+++ b/editor/libeditor/tests/test_root_element_replacement.html
@@ -90,7 +90,6 @@ function onLoadIFrame()
     getInterface(SpecialPowers.Ci.nsISelectionDisplay).
     QueryInterface(SpecialPowers.Ci.nsISelectionController);
   var utils = SpecialPowers.getDOMWindowUtils(window);
-  const nsIDOMNode = SpecialPowers.Ci.nsIDOMNode;
 
   // move focus to the HTML editor
   const kTest = kTests[gTestIndex];
@@ -110,9 +109,9 @@ function onLoadIFrame()
   var content = frameDoc.body.firstChild;
   ok(content, "body doesn't have contents -- " + kTest.description);
   if (content) {
-    is(content.nodeType, nsIDOMNode.TEXT_NODE,
+    is(content.nodeType, Node.TEXT_NODE,
        "the content of body isn't text node -- " + kTest.description);
-    if (content.nodeType == nsIDOMNode.TEXT_NODE) {
+    if (content.nodeType == Node.TEXT_NODE) {
       is(content.data, "ABC",
          "the content of body text isn't 'ABC' -- " + kTest.description);
       is(frameDoc.body.innerHTML, "ABC",
diff --git a/editor/nsIEditor.idl b/editor/nsIEditor.idl
index 8df3f9a39e8a..281039cb8770 100644
--- a/editor/nsIEditor.idl
+++ b/editor/nsIEditor.idl
@@ -21,6 +21,7 @@ interface nsITransferable;
 
 webidl Document;
 webidl Element;
+webidl Node;
 webidl Selection;
 
 %{C++
@@ -355,28 +356,25 @@ interface nsIEditor  : nsISupports
    * the destination node and delete those not in the source.
    *
    * The supplied nodes MUST BE ELEMENTS (most callers are working with nodes)
-   * @param aAttribute    the name of the attribute to copy
-   * @param aDestNode     the destination element to operate on
-   * @param aSourceNode   the source element to copy attributes from
-   * @exception NS_ERROR_NULL_POINTER at least one of the nodes is null
-   * @exception NS_ERROR_NO_INTERFACE at least one of the nodes is not an
-   *                                  element
+   * @param aAttribute     the name of the attribute to copy
+   * @param aDestElement   the destination element to operate on
+   * @param aSourceElement the source element to copy attributes from
+   * @exception NS_ERROR_NULL_POINTER at least one of the elements is null
    */
   void cloneAttribute(in AString aAttribute,
-                      in nsIDOMNode aDestNode, in nsIDOMNode aSourceNode);
+                      in Element aDestElement, in Element aSourceElement);
 
   /**
-   * cloneAttributes() is similar to nsIDOMNode::cloneNode(),
+   * cloneAttributes() is similar to Node::cloneNode(),
    *   it assures the attribute nodes of the destination are identical
    *   with the source node by copying all existing attributes from the
    *   source and deleting those not in the source.
-   *   This is used when the destination node (element) already exists
+   *   This is used when the destination element already exists
    *
-   * The supplied nodes MUST BE ELEMENTS (most callers are working with nodes)
    * @param aDestNode     the destination element to operate on
    * @param aSourceNode   the source element to copy attributes from
    */
-  void cloneAttributes(in nsIDOMNode destNode, in nsIDOMNode sourceNode);
+  void cloneAttributes(in Element aDestElement, in Element aSourceElement);
 
   /**
    * insertNode inserts aNode into aParent at aPosition.
@@ -388,9 +386,9 @@ interface nsIEditor  : nsISupports
    *                  0=first child, 1=second child, etc.
    *                  any number > number of current children = last child
    */
-  void insertNode(in nsIDOMNode node,
-                  in nsIDOMNode parent,
-                  in long       aPosition);
+  void insertNode(in Node node,
+                  in Node parent,
+                  in long aPosition);
 
 
   /**
@@ -403,9 +401,9 @@ interface nsIEditor  : nsISupports
    * @param aNewLeftNode         [OUT] the new node resulting from the split,
    *                             becomes aExistingRightNode's previous sibling.
    */
-  void splitNode(in nsIDOMNode existingRightNode,
-                 in long      offset,
-                 out nsIDOMNode newLeftNode);
+  void splitNode(in Node existingRightNode,
+                 in long offset,
+                 out Node newLeftNode);
 
   /**
    * joinNodes() takes 2 nodes and merge their content|children.
@@ -417,22 +415,22 @@ interface nsIEditor  : nsISupports
    *                      of the same type.  However, a text node can be
    *                      merged only with another text node.
    */
-  void joinNodes(in nsIDOMNode leftNode,
-                 in nsIDOMNode rightNode,
-                 in nsIDOMNode parent);
+  void joinNodes(in Node leftNode,
+                 in Node rightNode,
+                 in Node parent);
 
   /**
    * deleteNode removes aChild from aParent.
    * @param aChild    The node to delete
    */
-  void deleteNode(in nsIDOMNode child);
+  void deleteNode(in Node child);
 
   /**
    * markNodeDirty() sets a special dirty attribute on the node.
    * Usually this will be called immediately after creating a new node.
    * @param aNode      The node for which to insert formatting.
    */
-  void markNodeDirty(in nsIDOMNode node);
+  void markNodeDirty(in Node node);
 
 /* ---------- direction controller ---------- */
 
diff --git a/editor/spellchecker/TextServicesDocument.cpp b/editor/spellchecker/TextServicesDocument.cpp
index c635f2a83d2f..9b3bfce3ab87 100644
--- a/editor/spellchecker/TextServicesDocument.cpp
+++ b/editor/spellchecker/TextServicesDocument.cpp
@@ -20,7 +20,6 @@
 #include "nsIContent.h"                 // for nsIContent, etc
 #include "nsIContentIterator.h"         // for nsIContentIterator
 #include "nsID.h"                       // for NS_GET_IID
-#include "nsIDOMNode.h"                 // for nsIDOMNode, etc
 #include "nsIEditor.h"                  // for nsIEditor, etc
 #include "nsINode.h"                    // for nsINode
 #include "nsIPlaintextEditor.h"         // for nsIPlaintextEditor
@@ -1914,16 +1913,6 @@ TextServicesDocument::IsTextNode(nsIContent* aContent)
   return nsINode::TEXT_NODE == aContent->NodeType();
 }
 
-// static
-bool
-TextServicesDocument::IsTextNode(nsIDOMNode* aNode)
-{
-  NS_ENSURE_TRUE(aNode, false);
-
-  nsCOMPtr<nsIContent> content = do_QueryInterface(aNode);
-  return IsTextNode(content);
-}
-
 nsresult
 TextServicesDocument::SetSelectionInternal(int32_t aOffset,
                                            int32_t aLength,
diff --git a/editor/spellchecker/TextServicesDocument.h b/editor/spellchecker/TextServicesDocument.h
index b59378840b85..5ed8f93efaa4 100644
--- a/editor/spellchecker/TextServicesDocument.h
+++ b/editor/spellchecker/TextServicesDocument.h
@@ -16,7 +16,6 @@
 
 class nsIContent;
 class nsIContentIterator;
-class nsIDOMNode;
 class nsIEditor;
 class nsINode;
 class nsISelectionController;
@@ -262,7 +261,6 @@ private:
 
   static bool IsBlockNode(nsIContent* aContent);
   static bool IsTextNode(nsIContent* aContent);
-  static bool IsTextNode(nsIDOMNode* aNode);
 
   static bool DidSkip(nsIContentIterator* aFilteredIter);
   static void ClearDidSkip(nsIContentIterator* aFilteredIter);
diff --git a/editor/spellchecker/nsFilteredContentIterator.cpp b/editor/spellchecker/nsFilteredContentIterator.cpp
index a491e3cdafd4..3fea0e741a60 100644
--- a/editor/spellchecker/nsFilteredContentIterator.cpp
+++ b/editor/spellchecker/nsFilteredContentIterator.cpp
@@ -13,7 +13,6 @@
 #include "nsAtom.h"
 #include "nsIContent.h"
 #include "nsIContentIterator.h"
-#include "nsIDOMNode.h"
 #include "nsINode.h"
 #include "nsISupportsBase.h"
 #include "nsISupportsUtils.h"
diff --git a/editor/spellchecker/nsFilteredContentIterator.h b/editor/spellchecker/nsFilteredContentIterator.h
index 70bea9e9b7d9..4579e15f03f3 100644
--- a/editor/spellchecker/nsFilteredContentIterator.h
+++ b/editor/spellchecker/nsFilteredContentIterator.h
@@ -13,7 +13,6 @@
 #include "nscore.h"
 
 class nsAtom;
-class nsIDOMNode;
 class nsINode;
 class nsITextServicesFilter;
 class nsRange;