diff --git a/layout/style/nsCSSPropList.h b/layout/style/nsCSSPropList.h
index aaf2ee39df..b4a24ca0d1 100644
--- a/layout/style/nsCSSPropList.h
+++ b/layout/style/nsCSSPropList.h
@@ -4553,6 +4553,28 @@ CSS_PROP_POSITION(
     nullptr,
     offsetof(nsStylePosition, mZIndex),
     eStyleAnimType_Coord)
+CSS_PROP_DISPLAY(
+    overflow-block,
+    overflow_block,
+    OverflowBlock,
+    CSS_PROPERTY_PARSE_VALUE |
+        CSS_PROPERTY_APPLIES_TO_PLACEHOLDER,
+    "",
+    VARIANT_HK,
+    kOverflowSubKTable,
+    CSS_PROP_NO_OFFSET,
+    eStyleAnimType_Discrete)
+CSS_PROP_DISPLAY(
+    overflow-inline,
+    overflow_inline,
+    OverflowInline,
+    CSS_PROPERTY_PARSE_VALUE |
+        CSS_PROPERTY_APPLIES_TO_PLACEHOLDER,
+    "",
+    VARIANT_HK,
+    kOverflowSubKTable,
+    CSS_PROP_NO_OFFSET,
+    eStyleAnimType_Discrete)
 
 
 #ifdef USED_CSS_PROP
diff --git a/layout/style/nsComputedDOMStyle.cpp b/layout/style/nsComputedDOMStyle.cpp
index ceeb763c87..686ea6a1f5 100644
--- a/layout/style/nsComputedDOMStyle.cpp
+++ b/layout/style/nsComputedDOMStyle.cpp
@@ -6791,4 +6791,56 @@ nsComputedDOMStyle::UnregisterPrefChangeCallbacks()
 #undef UNREGISTER_CALLBACK
 }
 
+already_AddRefed<CSSValue>
+nsComputedDOMStyle::DoGetOverflowBlock()
+{
+  RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
+  uint8_t writingMode = StyleVisibility()->mWritingMode;
+  bool isVertical = writingMode == NS_STYLE_WRITING_MODE_VERTICAL_LR ||
+                    writingMode == NS_STYLE_WRITING_MODE_VERTICAL_RL ||
+                    writingMode == NS_STYLE_WRITING_MODE_SIDEWAYS_LR ||
+                    writingMode == NS_STYLE_WRITING_MODE_SIDEWAYS_RL;
+  auto overflow = isVertical ? StyleDisplay()->mOverflowX : StyleDisplay()->mOverflowY;
+  val->SetIdent(nsCSSProps::ValueToKeywordEnum(overflow, nsCSSProps::kOverflowSubKTable));
+  return val.forget();
+}
+
+already_AddRefed<CSSValue>
+nsComputedDOMStyle::DoGetOverflowInline()
+{
+  RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
+  uint8_t writingMode = StyleVisibility()->mWritingMode;
+  bool isVertical = writingMode == NS_STYLE_WRITING_MODE_VERTICAL_LR ||
+                    writingMode == NS_STYLE_WRITING_MODE_VERTICAL_RL ||
+                    writingMode == NS_STYLE_WRITING_MODE_SIDEWAYS_LR ||
+                    writingMode == NS_STYLE_WRITING_MODE_SIDEWAYS_RL;
+  auto overflow = isVertical ? StyleDisplay()->mOverflowY : StyleDisplay()->mOverflowX;
+  val->SetIdent(nsCSSProps::ValueToKeywordEnum(overflow, nsCSSProps::kOverflowSubKTable));
+  return val.forget();
+}
+
+already_AddRefed<CSSValue>
+nsComputedDOMStyle::DoGetOverflowInlineStart()
+{
+  return DoGetOverflowInline();
+}
+
+already_AddRefed<CSSValue>
+nsComputedDOMStyle::DoGetOverflowInlineEnd()
+{
+  return DoGetOverflowInline();
+}
+
+already_AddRefed<CSSValue>
+nsComputedDOMStyle::DoGetOverflowBlockStart()
+{
+  return DoGetOverflowBlock();
+}
+
+already_AddRefed<CSSValue>
+nsComputedDOMStyle::DoGetOverflowBlockEnd()
+{
+  return DoGetOverflowBlock();
+}
+
 
diff --git a/layout/style/nsComputedDOMStyle.h b/layout/style/nsComputedDOMStyle.h
index f256d22a50..718a38ff47 100644
--- a/layout/style/nsComputedDOMStyle.h
+++ b/layout/style/nsComputedDOMStyle.h
@@ -461,6 +461,12 @@ private:
   already_AddRefed<CSSValue> DoGetOverflow();
   already_AddRefed<CSSValue> DoGetOverflowX();
   already_AddRefed<CSSValue> DoGetOverflowY();
+  already_AddRefed<CSSValue> DoGetOverflowInline();
+  already_AddRefed<CSSValue> DoGetOverflowBlock();
+  already_AddRefed<CSSValue> DoGetOverflowInlineStart();
+  already_AddRefed<CSSValue> DoGetOverflowInlineEnd();
+  already_AddRefed<CSSValue> DoGetOverflowBlockStart();
+  already_AddRefed<CSSValue> DoGetOverflowBlockEnd();
   already_AddRefed<CSSValue> DoGetOverflowClipBox();
   already_AddRefed<CSSValue> DoGetResize();
   already_AddRefed<CSSValue> DoGetPageBreakAfter();
diff --git a/layout/style/nsComputedDOMStylePropertyList.h b/layout/style/nsComputedDOMStylePropertyList.h
index a17a6a8223..db0a68c660 100644
--- a/layout/style/nsComputedDOMStylePropertyList.h
+++ b/layout/style/nsComputedDOMStylePropertyList.h
@@ -199,6 +199,8 @@ COMPUTED_STYLE_PROP(overflow_clip_box,             OverflowClipBox)
 COMPUTED_STYLE_PROP(overflow_wrap,                 OverflowWrap)
 COMPUTED_STYLE_PROP(overflow_x,                    OverflowX)
 COMPUTED_STYLE_PROP(overflow_y,                    OverflowY)
+COMPUTED_STYLE_PROP(overflow_inline,               OverflowInline)
+COMPUTED_STYLE_PROP(overflow_block,                OverflowBlock)
 //// COMPUTED_STYLE_PROP(padding,                  Padding)
 COMPUTED_STYLE_PROP(padding_bottom,                PaddingBottom)
 COMPUTED_STYLE_PROP(padding_left,                  PaddingLeft)
diff --git a/layout/style/nsRuleNode.cpp b/layout/style/nsRuleNode.cpp
index 7a88ec1a27..a0a5ec1fd6 100644
--- a/layout/style/nsRuleNode.cpp
+++ b/layout/style/nsRuleNode.cpp
@@ -6405,6 +6405,27 @@ nsRuleNode::ComputeDisplayData(void* aStartStruct,
            SETVAL_ENUMERATED | SETVAL_UNSET_INITIAL,
            parentDisplay->mOverflowY,
            NS_STYLE_OVERFLOW_VISIBLE);
+  
+  // overflow-inline: enum, inherit, initial
+  // For simplicity, map overflow-inline to overflow-x for now (horizontal writing mode assumption)
+  const nsCSSValue* overflowInlineValue = aRuleData->ValueForOverflowInline();
+  if (overflowInlineValue->GetUnit() != eCSSUnit_Null) {
+    SetValue(*overflowInlineValue,
+             display->mOverflowX, conditions,
+             SETVAL_ENUMERATED | SETVAL_UNSET_INITIAL,
+             parentDisplay->mOverflowX,
+             NS_STYLE_OVERFLOW_VISIBLE);
+  }
+  // overflow-block: enum, inherit, initial
+  // For simplicity, map overflow-block to overflow-y for now (horizontal writing mode assumption)
+  const nsCSSValue* overflowBlockValue = aRuleData->ValueForOverflowBlock();
+  if (overflowBlockValue->GetUnit() != eCSSUnit_Null) {
+    SetValue(*overflowBlockValue,
+             display->mOverflowY, conditions,
+             SETVAL_ENUMERATED | SETVAL_UNSET_INITIAL,
+             parentDisplay->mOverflowY,
+             NS_STYLE_OVERFLOW_VISIBLE);
+  }
 
   // The visible/clip values of overflow compute to auto/hidden (respectively)
   // if one of overflow-x or overflow-y is neither visible nor clip.