diff --git a/.vscode/settings.json b/.vscode/settings.json
index 5a97ba29cee..5312b7ed5b4 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -5,6 +5,7 @@
     "editor.formatOnSave": true,
     "files.associations": {
         ".clang-format": "yaml",
+        "header-units.json": "jsonc",
         "**/stl/inc/**": "cpp"
     },
     "files.eol": "\r\n",
diff --git a/stl/CMakeLists.txt b/stl/CMakeLists.txt
index 394f28cd064..6f2686e6de2 100644
--- a/stl/CMakeLists.txt
+++ b/stl/CMakeLists.txt
@@ -146,6 +146,7 @@ set(HEADERS
     ${CMAKE_CURRENT_LIST_DIR}/inc/future
     ${CMAKE_CURRENT_LIST_DIR}/inc/hash_map
     ${CMAKE_CURRENT_LIST_DIR}/inc/hash_set
+    ${CMAKE_CURRENT_LIST_DIR}/inc/header-units.json
     ${CMAKE_CURRENT_LIST_DIR}/inc/initializer_list
     ${CMAKE_CURRENT_LIST_DIR}/inc/iomanip
     ${CMAKE_CURRENT_LIST_DIR}/inc/ios
diff --git a/stl/inc/header-units.json b/stl/inc/header-units.json
new file mode 100644
index 00000000000..cb1ef9efeb5
--- /dev/null
+++ b/stl/inc/header-units.json
@@ -0,0 +1,149 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+{
+    "Version": "1.0",
+    "BuildAsHeaderUnits": [
+        // "__msvc_all_public_headers.hpp", // for testing, not production
+        "__msvc_system_error_abi.hpp",
+        "algorithm",
+        "any",
+        "array",
+        "atomic",
+        "barrier",
+        "bit",
+        "bitset",
+        // "cassert", // design is permanently incompatible with header units
+        // "ccomplex", // removed in C++20
+        "cctype",
+        "cerrno",
+        "cfenv",
+        "cfloat",
+        "charconv",
+        "chrono",
+        "cinttypes",
+        // "ciso646", // removed in C++20
+        "climits",
+        "clocale",
+        "cmath",
+        "codecvt",
+        "compare",
+        "complex",
+        "concepts",
+        "condition_variable",
+        "coroutine",
+        "csetjmp",
+        "csignal",
+        // "cstdalign", // removed in C++20
+        "cstdarg",
+        // "cstdbool", // removed in C++20
+        "cstddef",
+        "cstdint",
+        "cstdio",
+        "cstdlib",
+        "cstring",
+        // "ctgmath", // removed in C++20
+        "ctime",
+        "cuchar",
+        "cwchar",
+        "cwctype",
+        "deque",
+        "exception",
+        "execution",
+        "filesystem",
+        "forward_list",
+        "fstream",
+        "functional",
+        "future",
+        // "hash_map", // non-Standard, will be removed soon
+        // "hash_set", // non-Standard, will be removed soon
+        "initializer_list",
+        "iomanip",
+        "ios",
+        "iosfwd",
+        "iostream",
+        "iso646.h",
+        "istream",
+        "iterator",
+        "latch",
+        "limits",
+        "list",
+        "locale",
+        "map",
+        "memory",
+        "memory_resource",
+        "mutex",
+        "new",
+        "numbers",
+        "numeric",
+        "optional",
+        "ostream",
+        "queue",
+        "random",
+        "ranges",
+        "ratio",
+        "regex",
+        "scoped_allocator",
+        "semaphore",
+        "set",
+        "shared_mutex",
+        "span",
+        "sstream",
+        "stack",
+        "stdexcept",
+        "stop_token",
+        "streambuf",
+        "string",
+        "string_view",
+        "strstream",
+        "system_error",
+        "thread",
+        "tuple",
+        "type_traits",
+        "typeindex",
+        "typeinfo",
+        "unordered_map",
+        "unordered_set",
+        "use_ansi.h",
+        "utility",
+        "valarray",
+        "variant",
+        "vector",
+        "version",
+        "xatomic.h",
+        "xatomic_wait.h",
+        "xbit_ops.h",
+        "xcall_once.h",
+        "xcharconv.h",
+        "xcharconv_ryu.h",
+        "xcharconv_ryu_tables.h",
+        "xerrc.h",
+        "xfacet",
+        "xfilesystem_abi.h",
+        "xhash",
+        "xiosbase",
+        // "xkeycheck.h", // internal header, provides no machinery, scans for macroized keywords only
+        "xlocale",
+        "xlocbuf",
+        "xlocinfo",
+        "xlocinfo.h",
+        "xlocmes",
+        "xlocmon",
+        "xlocnum",
+        "xloctime",
+        "xmemory",
+        "xnode_handle.h",
+        "xpolymorphic_allocator.h",
+        "xsmf_control.h",
+        "xstddef",
+        "xstring",
+        "xthreads.h",
+        "xtimec.h",
+        "xtr1common",
+        "xtree",
+        "xutility",
+        "ymath.h",
+        "yvals.h",
+        "yvals_core.h"
+    ]
+}