diff --git a/clang/include/clang/ExtractAPI/Serialization/SymbolGraphSerializer.h b/clang/include/clang/ExtractAPI/Serialization/SymbolGraphSerializer.h
--- a/clang/include/clang/ExtractAPI/Serialization/SymbolGraphSerializer.h
+++ b/clang/include/clang/ExtractAPI/Serialization/SymbolGraphSerializer.h
@@ -88,6 +88,10 @@
     /// The source symbol conforms to the target symbol.
     /// For example Objective-C protocol conformances.
     ConformsTo,
+
+    /// The source symbol is an extension to the target symbol.
+    /// For example Objective-C categories extending an external type.
+    ExtensionTo,
   };
 
   /// Get the string representation of the relationship kind.
diff --git a/clang/lib/ExtractAPI/Serialization/SymbolGraphSerializer.cpp b/clang/lib/ExtractAPI/Serialization/SymbolGraphSerializer.cpp
--- a/clang/lib/ExtractAPI/Serialization/SymbolGraphSerializer.cpp
+++ b/clang/lib/ExtractAPI/Serialization/SymbolGraphSerializer.cpp
@@ -216,11 +216,7 @@
 /// references, and the interface language name.
 Object serializeIdentifier(const APIRecord &Record, Language Lang) {
   Object Identifier;
-  if (auto *CategoryRecord =
-          dyn_cast_or_null<const ObjCCategoryRecord>(&Record))
-    Identifier["precise"] = CategoryRecord->Interface.USR;
-  else
-    Identifier["precise"] = Record.USR;
+  Identifier["precise"] = Record.USR;
   Identifier["interfaceLanguage"] = getLanguageName(Lang);
 
   return Identifier;
@@ -661,6 +657,8 @@
     return "inheritsFrom";
   case RelationshipKind::ConformsTo:
     return "conformsTo";
+  case RelationshipKind::ExtensionTo:
+    return "extensionTo";
   }
   llvm_unreachable("Unhandled relationship kind");
 }
@@ -755,7 +753,7 @@
   if (!Record.IsFromExternalModule)
     return;
 
-  // Check if the current Category Record has been visited before, if not add.
+  // Check if the current Category' parent has been visited before, if so skip.
   if (!(visitedCategories.contains(Record.Interface.Name) > 0)) {
     visitedCategories.insert(Record.Interface.Name);
     Object Obj;
@@ -772,7 +770,7 @@
   Relationship["source"] = Record.USR;
   Relationship["target"] = Record.Interface.USR;
   Relationship["targetFallback"] = Record.Interface.Name;
-  Relationship["kind"] = getRelationshipString(RelationshipKind::MemberOf);
+  Relationship["kind"] = getRelationshipString(RelationshipKind::ExtensionTo);
   Relationships.emplace_back(std::move(Relationship));
 
   auto ObjCCategory = serializeAPIRecord(Record);
diff --git a/clang/test/ExtractAPI/objc_module_category.m b/clang/test/ExtractAPI/objc_module_category.m
--- a/clang/test/ExtractAPI/objc_module_category.m
+++ b/clang/test/ExtractAPI/objc_module_category.m
@@ -53,7 +53,7 @@
   },
   "relationships": [
     {
-      "kind": "memberOf",
+      "kind": "extensionTo",
       "source": "c:objc(cy)NSString@Category1",
       "target": "c:objc(cs)NSString",
       "targetFallback": "NSString"
@@ -65,7 +65,7 @@
       "targetFallback": "Category1"
     },
     {
-      "kind": "memberOf",
+      "kind": "extensionTo",
       "source": "c:objc(cy)NSString@Category2",
       "target": "c:objc(cs)NSString",
       "targetFallback": "NSString"
@@ -82,7 +82,7 @@
       "accessLevel": "public",
       "identifier": {
         "interfaceLanguage": "objective-c",
-        "precise": "c:objc(cs)NSString"
+        "precise": "c:objc(cy)NSString@Category1"
       },
       "kind": {
         "displayName": "Module Extension",
@@ -137,7 +137,7 @@
       },
       "identifier": {
         "interfaceLanguage": "objective-c",
-        "precise": "c:objc(cs)NSString"
+        "precise": "c:objc(cy)NSString@Category1"
       },
       "kind": {
         "displayName": "Class Extension",
@@ -290,7 +290,7 @@
       },
       "identifier": {
         "interfaceLanguage": "objective-c",
-        "precise": "c:objc(cs)NSString"
+        "precise": "c:objc(cy)NSString@Category2"
       },
       "kind": {
         "displayName": "Class Extension",
diff --git a/clang/test/ExtractAPI/objc_various_categories.m b/clang/test/ExtractAPI/objc_various_categories.m
--- a/clang/test/ExtractAPI/objc_various_categories.m
+++ b/clang/test/ExtractAPI/objc_various_categories.m
@@ -77,7 +77,7 @@
       "targetFallback": "MyClass1"
     },
     {
-      "kind": "memberOf",
+      "kind": "extensionTo",
       "source": "c:objc(cy)MyClass2@MyCategory2",
       "target": "c:objc(cs)MyClass2",
       "targetFallback": "MyClass2"
@@ -89,7 +89,7 @@
       "targetFallback": "MyCategory2"
     },
     {
-      "kind": "memberOf",
+      "kind": "extensionTo",
       "source": "c:objc(cy)NSString@Category1",
       "target": "c:objc(cs)NSString",
       "targetFallback": "NSString"
@@ -101,7 +101,7 @@
       "targetFallback": "Category1"
     },
     {
-      "kind": "memberOf",
+      "kind": "extensionTo",
       "source": "c:objc(cy)NSString@Category2",
       "target": "c:objc(cs)NSString",
       "targetFallback": "NSString"
@@ -241,7 +241,7 @@
       "accessLevel": "public",
       "identifier": {
         "interfaceLanguage": "objective-c",
-        "precise": "c:objc(cs)MyClass2"
+        "precise": "c:objc(cy)MyClass2@MyCategory2"
       },
       "kind": {
         "displayName": "Module Extension",
@@ -279,7 +279,7 @@
       ],
       "identifier": {
         "interfaceLanguage": "objective-c",
-        "precise": "c:objc(cs)MyClass2"
+        "precise": "c:objc(cy)MyClass2@MyCategory2"
       },
       "kind": {
         "displayName": "Class Extension",
@@ -388,7 +388,7 @@
       "accessLevel": "public",
       "identifier": {
         "interfaceLanguage": "objective-c",
-        "precise": "c:objc(cs)NSString"
+        "precise": "c:objc(cy)NSString@Category1"
       },
       "kind": {
         "displayName": "Module Extension",
@@ -426,7 +426,7 @@
       ],
       "identifier": {
         "interfaceLanguage": "objective-c",
-        "precise": "c:objc(cs)NSString"
+        "precise": "c:objc(cy)NSString@Category1"
       },
       "kind": {
         "displayName": "Class Extension",
@@ -562,7 +562,7 @@
       ],
       "identifier": {
         "interfaceLanguage": "objective-c",
-        "precise": "c:objc(cs)NSString"
+        "precise": "c:objc(cy)NSString@Category2"
       },
       "kind": {
         "displayName": "Class Extension",