diff --git a/devtools/shared/css/generated/properties-db.js b/devtools/shared/css/generated/properties-db.js
index e3ec51466..994dd9348 100644
--- a/devtools/shared/css/generated/properties-db.js
+++ b/devtools/shared/css/generated/properties-db.js
@@ -6994,6 +6994,26 @@ exports.CSS_PROPERTIES = {
       "unset"
     ]
   },
+  "inset-block": {
+    "isInherited": false,
+    "subproperties": [
+      "inset-block-start",
+      "inset-block-end"
+    ],
+    "supports": [
+      6,
+      8
+    ],
+    "values": [
+      "-moz-calc",
+      "auto",
+      "calc",
+      "inherit",
+      "initial",
+      "revert",
+      "unset"
+    ]
+  },
   "inset-block-end": {
     "isInherited": false,
     "subproperties": [
@@ -7032,6 +7052,26 @@ exports.CSS_PROPERTIES = {
       "unset"
     ]
   },
+  "inset-inline": {
+    "isInherited": false,
+    "subproperties": [
+      "inset-inline-start",
+      "inset-inline-end"
+    ],
+    "supports": [
+      6,
+      8
+    ],
+    "values": [
+      "-moz-calc",
+      "auto",
+      "calc",
+      "inherit",
+      "initial",
+      "revert",
+      "unset"
+    ]
+  },
   "inset-inline-end": {
     "isInherited": false,
     "subproperties": [
diff --git a/layout/style/Declaration.cpp b/layout/style/Declaration.cpp
index a1634fccb..8c89ee3b4 100644
--- a/layout/style/Declaration.cpp
+++ b/layout/style/Declaration.cpp
@@ -1559,6 +1559,8 @@ Declaration::GetPropertyValueInternal(
       }
       MOZ_FALLTHROUGH;
     }
+    case eCSSProperty_inset_block:
+    case eCSSProperty_inset_inline:
     case eCSSProperty_margin_block:
     case eCSSProperty_margin_inline:
     case eCSSProperty_padding_block:
diff --git a/layout/style/nsCSSParser.cpp b/layout/style/nsCSSParser.cpp
index 559934869..7dd8f0041 100644
--- a/layout/style/nsCSSParser.cpp
+++ b/layout/style/nsCSSParser.cpp
@@ -1077,6 +1077,8 @@ protected:
   bool ParseFontSrcFormat(InfallibleTArray<nsCSSValue>& values);
   bool ParseFontRanges(nsCSSValue& aValue);
   bool ParseInset();
+  bool ParseInsetBlock();
+  bool ParseInsetInline();
   bool ParseListStyle();
   bool ParseListStyleType(nsCSSValue& aValue);
   bool ParseMargin();
@@ -12673,6 +12675,10 @@ CSSParserImpl::ParsePropertyByFunction(nsCSSPropertyID aPropID)
     return ParseJustifyItems();
   case eCSSProperty_inset:
     return ParseInset();
+  case eCSSProperty_inset_block:
+    return ParseInsetBlock();
+  case eCSSProperty_inset_inline:
+    return ParseInsetInline();
   case eCSSProperty_list_style:
     return ParseListStyle();
   case eCSSProperty_margin:
@@ -16202,6 +16208,24 @@ CSSParserImpl::ParseInset()
   return ParseBoxProperties(kInsetSideIDs);
 }
 
+bool
+CSSParserImpl::ParseInsetBlock()
+{
+  return ParseBoxPairProperties(VARIANT_AUTO | VARIANT_INHERIT,
+                                VARIANT_AUTO | VARIANT_LPCALC,
+                                eCSSProperty_inset_block_start,
+                                eCSSProperty_inset_block_end);
+}
+
+bool
+CSSParserImpl::ParseInsetInline()
+{
+  return ParseBoxPairProperties(VARIANT_AUTO | VARIANT_INHERIT,
+                                VARIANT_AUTO | VARIANT_LPCALC,
+                                eCSSProperty_inset_inline_start,
+                                eCSSProperty_inset_inline_end);
+}
+
 bool
 CSSParserImpl::ParseListStyleType(nsCSSValue& aValue)
 {
diff --git a/layout/style/nsCSSPropList.h b/layout/style/nsCSSPropList.h
index d58d3f2e9..5306462e2 100644
--- a/layout/style/nsCSSPropList.h
+++ b/layout/style/nsCSSPropList.h
@@ -2999,6 +2999,12 @@ CSS_PROP_POSITION(
     kImageLayerPositionKTable,
     offsetof(nsStylePosition, mObjectPosition),
     eStyleAnimType_Custom)
+CSS_PROP_SHORTHAND(
+    inset-block,
+    inset_block,
+    InsetBlock,
+    CSS_PROPERTY_PARSE_FUNCTION,
+    "")
 CSS_PROP_LOGICAL(
     inset-block-end,
     inset_block_end,
@@ -3032,6 +3038,12 @@ CSS_PROP_LOGICAL(
     Position,
     CSS_PROP_NO_OFFSET,
     eStyleAnimType_None)
+CSS_PROP_SHORTHAND(
+    inset-inline,
+    inset_inline,
+    InsetInline,
+    CSS_PROPERTY_PARSE_FUNCTION,
+    "")
 CSS_PROP_LOGICAL(
     inset-inline-end,
     inset_inline_end,
diff --git a/layout/style/nsCSSProps.cpp b/layout/style/nsCSSProps.cpp
index 35fdcbc60..49f0b4c41 100644
--- a/layout/style/nsCSSProps.cpp
+++ b/layout/style/nsCSSProps.cpp
@@ -2866,6 +2866,18 @@ static const nsCSSPropertyID gInsetSubpropTable[] = {
   eCSSProperty_UNKNOWN
 };
 
+static const nsCSSPropertyID gInsetBlockSubpropTable[] = {
+  eCSSProperty_inset_block_start,
+  eCSSProperty_inset_block_end,
+  eCSSProperty_UNKNOWN
+};
+
+static const nsCSSPropertyID gInsetInlineSubpropTable[] = {
+  eCSSProperty_inset_inline_start,
+  eCSSProperty_inset_inline_end,
+  eCSSProperty_UNKNOWN
+};
+
 static const nsCSSPropertyID gListStyleSubpropTable[] = {
   eCSSProperty_list_style_type,
   eCSSProperty_list_style_image,