diff --git a/dom/base/nsRange.cpp b/dom/base/nsRange.cpp
index 1b420cd887..27d48aa6aa 100644
--- a/dom/base/nsRange.cpp
+++ b/dom/base/nsRange.cpp
@@ -33,6 +33,9 @@
 #include "mozilla/Telemetry.h"
 #include "mozilla/Likely.h"
 #include "nsCSSFrameConstructor.h"
+#include "nsStyleStruct.h"
+#include "nsStyleStructInlines.h"
+#include "nsComputedDOMStyle.h"
 
 using namespace mozilla;
 using namespace mozilla::dom;
@@ -3131,3 +3134,244 @@ nsRange::ExcludeNonSelectableNodes(nsTArray<nsRefPtr<nsRange>>* aOutRanges)
     }
   }
 }
+
+
+struct InnerTextAccumulator
+{
+  explicit InnerTextAccumulator(mozilla::dom::DOMString& aValue)
+    : mString(aValue.AsAString()), mRequiredLineBreakCount(0) {}
+  void FlushLineBreaks()
+  {
+    while (mRequiredLineBreakCount > 0) {
+      // Required line breaks at the start of the text are suppressed.
+      if (!mString.IsEmpty()) {
+        mString.Append('\n');
+      }
+      --mRequiredLineBreakCount;
+    }
+  }
+  void Append(char aCh)
+  {
+    Append(nsAutoString(aCh));
+  }
+  void Append(const nsAString& aString)
+  {
+    if (aString.IsEmpty()) {
+      return;
+    }
+    FlushLineBreaks();
+    mString.Append(aString);
+  }
+  void AddRequiredLineBreakCount(int8_t aCount)
+  {
+    mRequiredLineBreakCount = std::max(mRequiredLineBreakCount, aCount);
+  }
+
+  nsAString& mString;
+  int8_t mRequiredLineBreakCount;
+};
+
+static bool
+IsVisibleAndNotInReplacedElement(nsIFrame* aFrame)
+{
+  if (!aFrame || !aFrame->StyleVisibility()->IsVisible()) {
+    return false;
+  }
+  for (nsIFrame* f = aFrame->GetParent(); f; f = f->GetParent()) {
+    if (f->IsFrameOfType(nsIFrame::eReplaced) &&
+        !f->GetContent()->IsHTML(nsGkAtoms::button)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+static bool
+ElementIsVisible(Element* aElement)
+{
+  if (!aElement) {
+    return false;
+  }
+  nsRefPtr<nsStyleContext> sc = nsComputedDOMStyle::GetStyleContextForElement(
+    aElement, nullptr, nullptr);
+  return sc && sc->StyleVisibility()->IsVisible();
+}
+
+static void
+AppendTransformedText(InnerTextAccumulator& aResult,
+                      nsGenericDOMDataNode* aTextNode,
+                      int32_t aStart, int32_t aEnd)
+{
+  nsIFrame* frame = aTextNode->GetPrimaryFrame();
+  if (!IsVisibleAndNotInReplacedElement(frame)) {
+    return;
+  }
+  nsIFrame::RenderedText text = frame->GetRenderedText(aStart, aEnd);
+  aResult.Append(text.mString);
+}
+
+/**
+ * States for tree traversal. AT_NODE means that we are about to enter
+ * the current DOM node. AFTER_NODE means that we have just finished traversing
+ * the children of the current DOM node and are about to apply any
+ * "after processing the node's children" steps before we finish visiting
+ * the node.
+ */
+enum TreeTraversalState {
+  AT_NODE,
+  AFTER_NODE
+};
+
+static int8_t
+GetRequiredInnerTextLineBreakCount(nsIFrame* aFrame)
+{
+  if (aFrame->GetContent()->IsHTML(nsGkAtoms::p)) {
+    return 2;
+  }
+  const nsStyleDisplay* styleDisplay = aFrame->StyleDisplay();
+  if (styleDisplay->IsBlockOutside(aFrame) ||
+      styleDisplay->mDisplay == NS_STYLE_DISPLAY_TABLE_CAPTION) {
+    return 1;
+  }
+  return 0;
+}
+
+static bool
+IsLastCellOfRow(nsIFrame* aFrame)
+{
+  nsIAtom* type = aFrame->GetType();
+  if (type != nsGkAtoms::tableCellFrame &&
+      type != nsGkAtoms::bcTableCellFrame) {
+    return true;
+  }
+  for (nsIFrame* c = aFrame; c; c = c->GetNextContinuation()) {
+    if (c->GetNextSibling()) {
+      return false;
+    }
+  }
+  return true;
+}
+
+static bool
+IsLastRowOfRowGroup(nsIFrame* aFrame)
+{
+  if (aFrame->GetType() != nsGkAtoms::tableRowFrame) {
+    return true;
+  }
+  for (nsIFrame* c = aFrame; c; c = c->GetNextContinuation()) {
+    if (c->GetNextSibling()) {
+      return false;
+    }
+  }
+  return true;
+}
+
+static bool
+IsLastNonemptyRowGroupOfTable(nsIFrame* aFrame)
+{
+  if (aFrame->GetType() != nsGkAtoms::tableRowGroupFrame) {
+    return true;
+  }
+  for (nsIFrame* c = aFrame; c; c = c->GetNextContinuation()) {
+    for (nsIFrame* next = c->GetNextSibling(); next; next = next->GetNextSibling()) {
+      if (next->GetFirstPrincipalChild()) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
+void
+nsRange::GetInnerTextNoFlush(DOMString& aValue, ErrorResult& aError,
+                             nsIContent* aStartParent, uint32_t aStartOffset,
+                             nsIContent* aEndParent, uint32_t aEndOffset)
+{
+  InnerTextAccumulator result(aValue);
+  nsIContent* currentNode = aStartParent;
+  TreeTraversalState currentState = AFTER_NODE;
+  if (aStartParent->IsNodeOfType(nsINode::eTEXT)) {
+    auto t = static_cast<nsGenericDOMDataNode*>(aStartParent);
+    if (aStartParent == aEndParent) {
+      AppendTransformedText(result, t, aStartOffset, aEndOffset);
+      return;
+    }
+    AppendTransformedText(result, t, aStartOffset, t->TextLength());
+  } else {
+    if (uint32_t(aStartOffset) < aStartParent->GetChildCount()) {
+      currentNode = aStartParent->GetChildAt(aStartOffset);
+      currentState = AT_NODE;
+    }
+  }
+
+  nsIContent* endNode = aEndParent;
+  TreeTraversalState endState = AFTER_NODE;
+  if (aEndParent->IsNodeOfType(nsINode::eTEXT)) {
+    endState = AT_NODE;
+  } else {
+    if (uint32_t(aEndOffset) < aEndParent->GetChildCount()) {
+      endNode = aEndParent->GetChildAt(aEndOffset);
+      endState = AT_NODE;
+    }
+  }
+
+  while (currentNode != endNode || currentState != endState) {
+    nsIFrame* f = currentNode->GetPrimaryFrame();
+    bool isVisibleAndNotReplaced = IsVisibleAndNotInReplacedElement(f);
+    if (currentState == AT_NODE) {
+      bool isText = currentNode->IsNodeOfType(nsINode::eTEXT);
+      if (isText && currentNode->GetParent()->IsHTML(nsGkAtoms::rp) &&
+          ElementIsVisible(currentNode->GetParent()->AsElement())) {
+        nsAutoString str;
+        currentNode->GetTextContent(str, aError);
+        result.Append(str);
+      } else if (isVisibleAndNotReplaced) {
+        result.AddRequiredLineBreakCount(GetRequiredInnerTextLineBreakCount(f));
+        if (isText) {
+          nsIFrame::RenderedText text = f->GetRenderedText();
+          result.Append(text.mString);
+        }
+      }
+      nsIContent* child = currentNode->GetFirstChild();
+      if (child) {
+        currentNode = child;
+      } else {
+        currentState = AFTER_NODE;
+      }
+    } else {
+      if (isVisibleAndNotReplaced) {
+        if (currentNode->IsHTML(nsGkAtoms::br)) {
+          result.Append('\n');
+        }
+        switch (f->StyleDisplay()->mDisplay) {
+        case NS_STYLE_DISPLAY_TABLE_CELL:
+          if (!IsLastCellOfRow(f)) {
+            result.Append('\t');
+          }
+          break;
+        case NS_STYLE_DISPLAY_TABLE_ROW:
+          if (!IsLastRowOfRowGroup(f) ||
+              !IsLastNonemptyRowGroupOfTable(f->GetParent())) {
+            result.Append('\n');
+          }
+          break;
+        }
+        result.AddRequiredLineBreakCount(GetRequiredInnerTextLineBreakCount(f));
+      }
+      nsIContent* next = currentNode->GetNextSibling();
+      if (next) {
+        currentNode = next;
+        currentState = AT_NODE;
+      } else {
+        currentNode = currentNode->GetParent();
+      }
+    }
+  }
+
+  if (aEndParent->IsNodeOfType(nsINode::eTEXT)) {
+    nsGenericDOMDataNode* t = static_cast<nsGenericDOMDataNode*>(aEndParent);
+    AppendTransformedText(result, t, 0, aEndOffset);
+  }
+  // Do not flush trailing line breaks! Required breaks at the end of the text
+  // are suppressed.
+}
\ No newline at end of file
diff --git a/dom/base/nsRange.h b/dom/base/nsRange.h
index 0be4a903cd..e82628b3a5 100644
--- a/dom/base/nsRange.h
+++ b/dom/base/nsRange.h
@@ -242,6 +242,12 @@ public:
                                                   bool aFlushLayout = true);
   already_AddRefed<DOMRectList> GetClientRects(bool aClampToEdge = true,
                                                bool aFlushLayout = true);
+  static void GetInnerTextNoFlush(mozilla::dom::DOMString& aValue,
+                                  mozilla::ErrorResult& aError,
+                                  nsIContent* aStartParent,
+                                  uint32_t aStartOffset,
+                                  nsIContent* aEndParent,
+                                  uint32_t aEndOffset);
 
   nsINode* GetParentObject() const { return mOwner; }
   virtual JSObject* WrapObject(JSContext* cx) override final;
diff --git a/dom/html/nsGenericHTMLElement.cpp b/dom/html/nsGenericHTMLElement.cpp
index 966ed54db8..2c13e953e4 100644
--- a/dom/html/nsGenericHTMLElement.cpp
+++ b/dom/html/nsGenericHTMLElement.cpp
@@ -84,6 +84,8 @@
 #include "nsITextControlElement.h"
 #include "mozilla/dom/Element.h"
 #include "HTMLFieldSetElement.h"
+#include "nsTextNode.h"
+#include "HTMLBRElement.h"
 #include "HTMLMenuElement.h"
 #include "nsDOMMutationObserver.h"
 #include "mozilla/Preferences.h"
@@ -104,6 +106,7 @@
 #include "nsGlobalWindow.h"
 #include "mozilla/dom/HTMLBodyElement.h"
 #include "imgIContainer.h"
+#include "nsComputedDOMStyle.h"
 
 using namespace mozilla;
 using namespace mozilla::dom;
@@ -3220,3 +3223,77 @@ nsGenericHTMLElement::NewURIFromString(const nsAutoString& aURISpec,
 
   return NS_OK;
 }
+
+void
+nsGenericHTMLElement::GetInnerText(mozilla::dom::DOMString& aValue,
+                                   mozilla::ErrorResult& aError)
+{
+  if (!GetPrimaryFrame(Flush_Layout)) {
+    nsRefPtr<nsStyleContext> sc =
+      nsComputedDOMStyle::GetStyleContextForElementNoFlush(this, nullptr, nullptr);
+    if (!sc || sc->StyleDisplay()->mDisplay == NS_STYLE_DISPLAY_NONE ||
+        !IsInComposedDoc()) {
+      GetTextContentInternal(aValue, aError);
+      return;
+    }
+  }
+
+  nsRange::GetInnerTextNoFlush(aValue, aError, this, 0, this, GetChildCount());
+}
+
+void
+nsGenericHTMLElement::SetInnerText(const nsAString& aValue)
+{
+  // Fire DOMNodeRemoved mutation events before we do anything else.
+  nsCOMPtr<nsIContent> kungFuDeathGrip;
+
+  // Batch possible DOMSubtreeModified events.
+  mozAutoSubtreeModified subtree(OwnerDoc(), nullptr);
+  FireNodeRemovedForChildren();
+
+  // Might as well stick a batch around this since we're performing several
+  // mutations.
+  mozAutoDocUpdate updateBatch(GetComposedDoc(),
+    UPDATE_CONTENT_MODEL, true);
+  nsAutoMutationBatch mb;
+
+  uint32_t childCount = GetChildCount();
+
+  mb.Init(this, true, false);
+  for (uint32_t i = 0; i < childCount; ++i) {
+    RemoveChildAt(0, true);
+  }
+  mb.RemovalDone();
+
+  nsString str;
+  const char16_t* s = aValue.BeginReading();
+  const char16_t* end = aValue.EndReading();
+  while (true) {
+    if (s != end && *s == '\r' && s + 1 != end && s[1] == '\n') {
+      // a \r\n pair should only generate one <br>, so just skip the \r
+      ++s;
+    }
+    if (s == end || *s == '\r' || *s == '\n') {
+      if (!str.IsEmpty()) {
+        nsRefPtr<nsTextNode> textContent =
+          new nsTextNode(NodeInfo()->NodeInfoManager());
+        textContent->SetText(str, true);
+        AppendChildTo(textContent, true);
+      }
+      if (s == end) {
+        break;
+      }
+      str.Truncate();
+      already_AddRefed<mozilla::dom::NodeInfo> ni =
+        NodeInfo()->NodeInfoManager()->GetNodeInfo(nsGkAtoms::br,
+          nullptr, kNameSpaceID_XHTML, nsIDOMNode::ELEMENT_NODE);
+      nsRefPtr<HTMLBRElement> br = new HTMLBRElement(ni);
+      AppendChildTo(br, true);
+    } else {
+      str.Append(*s);
+    }
+    ++s;
+  }
+
+  mb.NodesAdded();
+}
diff --git a/dom/html/nsGenericHTMLElement.h b/dom/html/nsGenericHTMLElement.h
index 35181ef284..6028612e70 100644
--- a/dom/html/nsGenericHTMLElement.h
+++ b/dom/html/nsGenericHTMLElement.h
@@ -233,6 +233,9 @@ public:
     mScrollgrab = aValue;
   }
 
+  void GetInnerText(mozilla::dom::DOMString& aValue, mozilla::ErrorResult& aError);
+  void SetInnerText(const nsAString& aValue);
+
   /**
    * Determine whether an attribute is an event (onclick, etc.)
    * @param aName the attribute
diff --git a/dom/webidl/HTMLElement.webidl b/dom/webidl/HTMLElement.webidl
index 8399c1e7cb..7caf687854 100644
--- a/dom/webidl/HTMLElement.webidl
+++ b/dom/webidl/HTMLElement.webidl
@@ -22,6 +22,9 @@ interface HTMLElement : Element {
   [Constant]
   readonly attribute DOMStringMap dataset;
 
+  [GetterThrows, Pure]
+           attribute DOMString innerText;
+
   // microdata 
   [SetterThrows, Pure]
            attribute boolean itemScope;