diff --git a/memory/mozjemalloc/jemalloc.c b/memory/mozjemalloc/jemalloc.c
index 01c559a2bb..5e50d65f81 100644
--- a/memory/mozjemalloc/jemalloc.c
+++ b/memory/mozjemalloc/jemalloc.c
@@ -297,22 +297,9 @@ typedef long ssize_t;
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
-#ifndef MOZ_MEMORY_DARWIN
 #include <strings.h>
-#endif
 #include <unistd.h>
 
-#ifdef MOZ_MEMORY_DARWIN
-#include <libkern/OSAtomic.h>
-#include <mach/mach_error.h>
-#include <mach/mach_init.h>
-#include <mach/vm_map.h>
-#include <malloc/malloc.h>
-#ifndef _pthread_self
-#define _pthread_self() pthread_self()
-#endif
-#endif
-
 #endif
 
 #include "jemalloc_types.h"
diff --git a/netwerk/protocol/http/nsHttpHandler.cpp b/netwerk/protocol/http/nsHttpHandler.cpp
index b103ac66ad..de023beafa 100644
--- a/netwerk/protocol/http/nsHttpHandler.cpp
+++ b/netwerk/protocol/http/nsHttpHandler.cpp
@@ -826,15 +826,6 @@ nsHttpHandler::InitUserAgentComponents()
             PR_smprintf_free(buf);
         }
     }
-#elif defined (XP_MACOSX)
-#if defined(__ppc__)
-    mOscpu.AssignLiteral("PPC Mac OS X");
-#elif defined(__i386__) || defined(__x86_64__)
-    mOscpu.AssignLiteral("Intel Mac OS X");
-#endif
-    SInt32 majorVersion = nsCocoaFeatures::macOSVersionMajor();
-    SInt32 minorVersion = nsCocoaFeatures::macOSVersionMinor();
-    mOscpu += nsPrintfCString(" %d.%d", majorVersion, minorVersion);
 #elif defined (XP_UNIX)
     struct utsname name;
 
diff --git a/widget/GfxDriverInfo.h b/widget/GfxDriverInfo.h
index 17baf136d7..ad4337b0fb 100644
--- a/widget/GfxDriverInfo.h
+++ b/widget/GfxDriverInfo.h
@@ -49,21 +49,6 @@ enum class OperatingSystem {
   Windows8_1,
   Windows10,
   Linux,
-  OSX,
-  OSX10_5,
-  OSX10_6,
-  OSX10_7,
-  OSX10_8,
-  OSX10_9,
-  OSX10_10,
-  OSX10_11,
-  OSX10_12,
-  OSX10_13,
-  OSX10_14,
-  OSX10_15,
-  OSX10_16,
-  OSX11_0,
-  Ios
 };
 
 enum VersionComparisonOp {
diff --git a/widget/GfxInfoBase.cpp b/widget/GfxInfoBase.cpp
index 321ee87547..feafc37bde 100644
--- a/widget/GfxInfoBase.cpp
+++ b/widget/GfxInfoBase.cpp
@@ -263,30 +263,6 @@ BlacklistOSToOperatingSystem(const nsAString& os)
     return OperatingSystem::Windows10;
   else if (os.EqualsLiteral("Linux"))
     return OperatingSystem::Linux;
-  else if (os.EqualsLiteral("Darwin 9"))
-    return OperatingSystem::OSX10_5;
-  else if (os.EqualsLiteral("Darwin 10"))
-    return OperatingSystem::OSX10_6;
-  else if (os.EqualsLiteral("Darwin 11"))
-    return OperatingSystem::OSX10_7;
-  else if (os.EqualsLiteral("Darwin 12"))
-    return OperatingSystem::OSX10_8;
-  else if (os.EqualsLiteral("Darwin 13"))
-    return OperatingSystem::OSX10_9;
-  else if (os.EqualsLiteral("Darwin 14"))
-    return OperatingSystem::OSX10_10;
-  else if (os.EqualsLiteral("Darwin 15"))
-    return OperatingSystem::OSX10_11;
-  else if (os.EqualsLiteral("Darwin 16"))
-    return OperatingSystem::OSX10_12;
-  else if (os.EqualsLiteral("Darwin 17"))
-    return OperatingSystem::OSX10_13;
-  else if (os.EqualsLiteral("Darwin 18"))
-    return OperatingSystem::OSX10_14;
-  else if (os.EqualsLiteral("Darwin 19"))
-    return OperatingSystem::OSX10_15;
-  else if (os.EqualsLiteral("Darwin 20"))
-    return OperatingSystem::OSX11_0;
   // For historical reasons, "All" in blocklist means "All Windows"
   else if (os.EqualsLiteral("All"))
     return OperatingSystem::Windows;
diff --git a/xpcom/components/ManifestParser.cpp b/xpcom/components/ManifestParser.cpp
index f256354288..e3b0b0f3cc 100644
--- a/xpcom/components/ManifestParser.cpp
+++ b/xpcom/components/ManifestParser.cpp
@@ -539,12 +539,6 @@ ParseManifest(NSLocationType aType, FileLocation& aFile, char* aBuf,
                               info.dwMinorVersion);
   }
 #pragma warning(pop)
-#elif defined(MOZ_WIDGET_COCOA)
-  SInt32 majorVersion = nsCocoaFeatures::macOSVersionMajor();
-  SInt32 minorVersion = nsCocoaFeatures::macOSVersionMinor();
-  nsTextFormatter::ssprintf(osVersion, u"%ld.%ld",
-                            majorVersion,
-                            minorVersion);
 #elif defined(MOZ_WIDGET_GTK)
   nsTextFormatter::ssprintf(osVersion, u"%ld.%ld",
                             gtk_major_version,