diff --git a/.gitignore b/.gitignore
index 949cea02040ab..6f3b08c679167 100644
--- a/.gitignore
+++ b/.gitignore
@@ -46,3 +46,5 @@ ipch/
 *.VC.db*
 *.tds
 *.*codeanalysis*
+*.js
+*.wasm
diff --git a/ACE/ace/Notification_Queue.h b/ACE/ace/Notification_Queue.h
index 914904ac296fc..18749e4f2a221 100644
--- a/ACE/ace/Notification_Queue.h
+++ b/ACE/ace/Notification_Queue.h
@@ -13,6 +13,8 @@
 #include "ace/Intrusive_List.h"
 #include "ace/Intrusive_List_Node.h"
 #include "ace/Unbounded_Queue.h"
+#include "ace/Synch_Traits.h"
+#include "ace/Thread_Mutex.h"
 
 ACE_BEGIN_VERSIONED_NAMESPACE_DECL
 
diff --git a/ACE/ace/Timer_Queue_T.inl b/ACE/ace/Timer_Queue_T.inl
index 15c0e8ef99d5f..673820f2e1035 100644
--- a/ACE/ace/Timer_Queue_T.inl
+++ b/ACE/ace/Timer_Queue_T.inl
@@ -1,6 +1,10 @@
 // -*- C++ -*-
 ACE_BEGIN_VERSIONED_NAMESPACE_DECL
 
+#include "ace/Guard_T.h"
+
+ACE_BEGIN_VERSIONED_NAMESPACE_DECL
+
 template <class TYPE, class FUNCTOR> ACE_INLINE FUNCTOR &
 ACE_Timer_Queue_Upcall_Base<TYPE, FUNCTOR>::upcall_functor ()
 {
diff --git a/ACE/ace/config-emscripten.h b/ACE/ace/config-emscripten.h
new file mode 100644
index 0000000000000..f43c16b3a52f6
--- /dev/null
+++ b/ACE/ace/config-emscripten.h
@@ -0,0 +1,51 @@
+#ifndef ACE_CONFIG_EMSCRIPTEN_H
+#define ACE_CONFIG_EMSCRIPTEN_H
+
+#define ACE_EMSCRIPTEN
+
+#define ACE_HAS_CPP11
+
+// Threading
+#define ACE_MT_SAFE 1
+#define ACE_HAS_THREADS 1
+#define ACE_HAS_PTHREADS
+#define ACE_HAS_PTHREADS_UNIX98_EXT
+#define ACE_HAS_THREAD_SPECIFIC_STORAGE
+
+// Basic Types
+#define ACE_HAS_SSIZE_T
+#define ACE_HAS_WCHAR
+
+// Time
+#define ACE_HAS_POSIX_TIME
+#define ACE_LACKS_TIMESPEC_T
+#define ACE_HAS_NONCONST_SELECT_TIMEVAL
+#define ACE_HAS_VOIDPTR_GETTIMEOFDAY
+
+// Everything else
+#define ACE_HAS_UCONTEXT_T
+#define ACE_HAS_MSG
+#define ACE_HAS_CPU_SET_T
+#define ACE_LACKS_ISCTYPE
+#define ACE_HAS_STRBUF_T
+#define ACE_HAS_SOCKLEN_T
+#define ACE_LACKS_AUTO_PTR
+#define ACE_HAS_SIGINFO_T
+#define ACE_LACKS_SIGINFO_H
+#define ACE_HAS_CONSISTENT_SIGNAL_PROTOTYPES
+#define ACE_HAS_3_PARAM_WCSTOK
+#define ACE_LACKS_ITOW
+#define ACE_LACKS_WCSICMP
+#define ACE_LACKS_WCSNICMP
+#define ACE_HAS_DIRENT
+#define ACE_HAS_4_4BSD_SENDMSG_RECVMSG
+
+#include "config-posix.h"
+#include "config-g++-common.h"
+
+// Not supported? https://github.com/emscripten-core/emscripten/issues/18050
+#ifdef ACE_HAS_AIO_CALLS
+#  undef ACE_HAS_AIO_CALLS
+#endif
+
+#endif
diff --git a/ACE/ace/os_include/sys/os_types.h b/ACE/ace/os_include/sys/os_types.h
index 822c8a93d97db..7f39c8cc99957 100644
--- a/ACE/ace/os_include/sys/os_types.h
+++ b/ACE/ace/os_include/sys/os_types.h
@@ -66,7 +66,7 @@ typedef double ACE_timer_t;
 #if defined (ACE_SIZEOF_LONG) && ACE_SIZEOF_LONG == 8
    typedef off_t ACE_LOFF_T;
 #elif defined (ACE_HAS_RTEMS) || defined (__FreeBSD__) || defined (__NetBSD__) || defined (__OpenBSD__) || defined (__APPLE__) || \
-  (defined (ACE_OPENVMS) && defined (_LARGEFILE))
+  (defined (ACE_OPENVMS) && defined (_LARGEFILE)) || defined (ACE_EMSCRIPTEN)
    typedef off_t ACE_LOFF_T;
 #elif defined (AIX) || defined (HPUX) || defined (__QNX__)
    typedef off64_t ACE_LOFF_T;
diff --git a/ACE/include/makeinclude/platform_emscripten.GNU b/ACE/include/makeinclude/platform_emscripten.GNU
new file mode 100644
index 0000000000000..af6fa2bc14544
--- /dev/null
+++ b/ACE/include/makeinclude/platform_emscripten.GNU
@@ -0,0 +1,23 @@
+ACE_PLATFORM_CONFIG ?= config-emscripten.h
+EXEEXT = .js
+
+debug ?= 1
+optimize ?= 1
+threads ?= 1
+inline ?= 1
+static_libs_only = 1
+
+CROSS_COMPILE := THIS_VALUE_SHOULD_NOT_BE_USED
+override_cross_compile = 1
+CC = emcc
+CXX = em++
+AR = emar
+LD = emcc
+
+ifeq ($(threads),1)
+  FLAGS_C_CC += -pthread
+  SOFLAGS += -pthread
+  LIBS += -lrt
+endif
+
+include $(ACE_ROOT)/include/makeinclude/platform_clang_common.GNU