diff --git a/xpcom/components/nsCategoryManager.cpp b/xpcom/components/nsCategoryManager.cpp
index 527c78719053..ccdffbf956ab 100644
--- a/xpcom/components/nsCategoryManager.cpp
+++ b/xpcom/components/nsCategoryManager.cpp
@@ -113,8 +113,7 @@ BaseStringEnumerator::GetNext(nsISupports** aResult)
     return NS_ERROR_FAILURE;
   }
 
-  nsSupportsDependentCString* str =
-    new nsSupportsDependentCString(mArray[mSimpleCurItem++]);
+  auto* str = new nsSupportsDependentCString(mArray[mSimpleCurItem++]);
   if (!str) {
     return NS_ERROR_OUT_OF_MEMORY;
   }
@@ -173,7 +172,7 @@ public:
 EntryEnumerator*
 EntryEnumerator::Create(nsTHashtable<CategoryLeaf>& aTable)
 {
-  EntryEnumerator* enumObj = new EntryEnumerator();
+  auto* enumObj = new EntryEnumerator();
   if (!enumObj) {
     return nullptr;
   }
@@ -337,7 +336,7 @@ CategoryEnumerator*
 CategoryEnumerator::Create(nsClassHashtable<nsDepCharHashKey, CategoryNode>&
                            aTable)
 {
-  CategoryEnumerator* enumObj = new CategoryEnumerator();
+  auto* enumObj = new CategoryEnumerator();
   if (!enumObj) {
     return nullptr;
   }
diff --git a/xpcom/components/nsComponentManager.cpp b/xpcom/components/nsComponentManager.cpp
index 7108b8e0ad68..f839651d5837 100644
--- a/xpcom/components/nsComponentManager.cpp
+++ b/xpcom/components/nsComponentManager.cpp
@@ -721,7 +721,7 @@ nsComponentManagerImpl::ManifestComponent(ManifestProcessingContext& aCx,
   *permanentCID = cid;
 
   PL_ARENA_ALLOCATE(place, &mArena, sizeof(mozilla::Module::CIDEntry));
-  mozilla::Module::CIDEntry* e = new (place) mozilla::Module::CIDEntry();
+  auto* e = new (place) mozilla::Module::CIDEntry();
   e->cid = permanentCID;
 
   f = new nsFactoryEntry(e, km);
@@ -1691,7 +1691,7 @@ nsComponentManagerImpl::EnumerateCIDs(nsISimpleEnumerator** aEnumerator)
 NS_IMETHODIMP
 nsComponentManagerImpl::EnumerateContractIDs(nsISimpleEnumerator** aEnumerator)
 {
-  nsTArray<nsCString>* array = new nsTArray<nsCString>;
+  auto* array = new nsTArray<nsCString>;
   for (auto iter = mContractIDs.Iter(); !iter.Done(); iter.Next()) {
     const nsACString& contract = iter.Key();
     array->AppendElement(contract);
@@ -1803,8 +1803,8 @@ nsFactoryEntry::nsFactoryEntry(const nsCID& aCID, nsIFactory* aFactory)
   , mModule(nullptr)
   , mFactory(aFactory)
 {
-  mozilla::Module::CIDEntry* e = new mozilla::Module::CIDEntry();
-  nsCID* cid = new nsCID;
+  auto* e = new mozilla::Module::CIDEntry();
+  auto* cid = new nsCID;
   *cid = aCID;
   e->cid = cid;
   mCIDEntry = e;
diff --git a/xpcom/glue/nsEnumeratorUtils.cpp b/xpcom/glue/nsEnumeratorUtils.cpp
index d1843a78ad59..4af997648ad5 100644
--- a/xpcom/glue/nsEnumeratorUtils.cpp
+++ b/xpcom/glue/nsEnumeratorUtils.cpp
@@ -279,8 +279,8 @@ NS_NewUnionEnumerator(nsISimpleEnumerator** aResult,
   } else if (!aSecondEnumerator) {
     *aResult = aFirstEnumerator;
   } else {
-    nsUnionEnumerator* enumer = new nsUnionEnumerator(aFirstEnumerator,
-                                                      aSecondEnumerator);
+    auto* enumer = new nsUnionEnumerator(aFirstEnumerator,
+                                         aSecondEnumerator);
     if (!enumer) {
       return NS_ERROR_OUT_OF_MEMORY;
     }
diff --git a/xpcom/glue/nsTArray.cpp b/xpcom/glue/nsTArray.cpp
index a5b7704926d2..81a5799f18af 100644
--- a/xpcom/glue/nsTArray.cpp
+++ b/xpcom/glue/nsTArray.cpp
@@ -26,7 +26,7 @@ InvalidArrayIndex_CRASH(size_t aIndex, size_t aLength)
   // Leak the buffer on the heap to make sure that it lives long enough, as
   // MOZ_CRASH_ANNOTATE expects the pointer passed to it to live to the end of
   // the program.
-  char* buffer = new char[CAPACITY];
+  auto* buffer = new char[CAPACITY];
   snprintf(buffer, CAPACITY,
            "ElementAt(aIndex = %llu, aLength = %llu)",
            (long long unsigned) aIndex,
diff --git a/xpcom/glue/standalone/nsXPCOMGlue.cpp b/xpcom/glue/standalone/nsXPCOMGlue.cpp
index b657d7050e88..58dc856acde1 100644
--- a/xpcom/glue/standalone/nsXPCOMGlue.cpp
+++ b/xpcom/glue/standalone/nsXPCOMGlue.cpp
@@ -134,7 +134,7 @@ static DependentLib* sTop;
 static void
 AppendDependentLib(LibHandleType aLibHandle)
 {
-  DependentLib* d = new DependentLib;
+  auto* d = new DependentLib;
   if (!d) {
     return;
   }
diff --git a/xpcom/io/nsLocalFileUnix.cpp b/xpcom/io/nsLocalFileUnix.cpp
index 494752df7043..b509bd96228a 100644
--- a/xpcom/io/nsLocalFileUnix.cpp
+++ b/xpcom/io/nsLocalFileUnix.cpp
@@ -827,7 +827,7 @@ nsLocalFile::CopyToNative(nsIFile* aNewParent, const nsACString& aNewName)
 #endif
 
     // actually create the file.
-    nsLocalFile* newFile = new nsLocalFile();
+    auto* newFile = new nsLocalFile();
     nsCOMPtr<nsIFile> fileRef(newFile); // release on exit
 
     rv = newFile->InitWithNativePath(newPathName);
@@ -1040,7 +1040,7 @@ nsLocalFile::Remove(bool aRecursive)
   }
 
   if (aRecursive) {
-    nsDirEnumeratorUnix* dir = new nsDirEnumeratorUnix();
+    auto* dir = new nsDirEnumeratorUnix();
 
     nsCOMPtr<nsISimpleEnumerator> dirRef(dir); // release on exit
 
diff --git a/xpcom/tests/gtest/TestCOMPtr.cpp b/xpcom/tests/gtest/TestCOMPtr.cpp
index e17331c65e91..c74436fdf896 100644
--- a/xpcom/tests/gtest/TestCOMPtr.cpp
+++ b/xpcom/tests/gtest/TestCOMPtr.cpp
@@ -102,7 +102,7 @@ nsresult
 CreateIFoo( void** result )
 // a typical factory function (that calls AddRef)
 {
-  IFoo* foop = new IFoo;
+  auto* foop = new IFoo;
 
   foop->AddRef();
   *result = foop;
@@ -190,7 +190,7 @@ nsresult
 CreateIBar( void** result )
   // a typical factory function (that calls AddRef)
 {
-  IBar* barp = new IBar;
+  auto* barp = new IBar;
 
   barp->AddRef();
   *result = barp;
@@ -332,10 +332,10 @@ void Comparison()
 void DontAddRef()
 {
   {
-    IFoo* raw_foo1p = new IFoo;
+    auto* raw_foo1p = new IFoo;
     raw_foo1p->AddRef();
 
-    IFoo* raw_foo2p = new IFoo;
+    auto* raw_foo2p = new IFoo;
     raw_foo2p->AddRef();
 
     nsCOMPtr<IFoo> foo1p( dont_AddRef(raw_foo1p) );
diff --git a/xpcom/tests/gtest/TestHashtables.cpp b/xpcom/tests/gtest/TestHashtables.cpp
index 13bd15128cd2..9687b1b6e05c 100644
--- a/xpcom/tests/gtest/TestHashtables.cpp
+++ b/xpcom/tests/gtest/TestHashtables.cpp
@@ -246,7 +246,7 @@ nsresult
 CreateIFoo( IFoo** result )
     // a typical factory function (that calls AddRef)
   {
-    IFoo* foop = new IFoo();
+    auto* foop = new IFoo();
 
     foop->AddRef();
     *result = foop;
@@ -318,7 +318,7 @@ TEST(Hashtables, ClassHashtable)
   nsClassHashtable<nsCStringHashKey,TestUniChar> EntToUniClass(ENTITY_COUNT);
 
   for (auto& entity : gEntities) {
-    TestUniChar* temp = new TestUniChar(entity.mUnicode);
+    auto* temp = new TestUniChar(entity.mUnicode);
     EntToUniClass.Put(nsDependentCString(entity.mStr), temp);
   }
 
diff --git a/xpcom/tests/gtest/TestNsRefPtr.cpp b/xpcom/tests/gtest/TestNsRefPtr.cpp
index a085c29660f7..c340a7ed2702 100644
--- a/xpcom/tests/gtest/TestNsRefPtr.cpp
+++ b/xpcom/tests/gtest/TestNsRefPtr.cpp
@@ -128,7 +128,7 @@ nsresult
 CreateFoo( void** result )
   // a typical factory function (that calls AddRef)
 {
-  Foo* foop = new Foo;
+  auto* foop = new Foo;
 
   foop->AddRef();
   *result = foop;
@@ -331,10 +331,10 @@ TEST(nsRefPtr, AddRefHelpers)
   Foo::total_addrefs_ = 0;
 
   {
-    Foo* raw_foo1p = new Foo;
+    auto* raw_foo1p = new Foo;
     raw_foo1p->AddRef();
 
-    Foo* raw_foo2p = new Foo;
+    auto* raw_foo2p = new Foo;
     raw_foo2p->AddRef();
 
     ASSERT_EQ(Foo::total_addrefs_, 2);