diff --git a/ci/licenses_golden/licenses_flutter b/ci/licenses_golden/licenses_flutter
index a854944969fbf..45901aa51c07e 100755
--- a/ci/licenses_golden/licenses_flutter
+++ b/ci/licenses_golden/licenses_flutter
@@ -285,7 +285,9 @@ FILE: ../../../flutter/fml/platform/win/message_loop_win.h
 FILE: ../../../flutter/fml/platform/win/native_library_win.cc
 FILE: ../../../flutter/fml/platform/win/paths_win.cc
 FILE: ../../../flutter/fml/platform/win/posix_wrappers_win.cc
+FILE: ../../../flutter/fml/platform/win/wstring_conversion.cc
 FILE: ../../../flutter/fml/platform/win/wstring_conversion.h
+FILE: ../../../flutter/fml/platform/win/wstring_conversion_unittests.cc
 FILE: ../../../flutter/fml/posix_wrappers.h
 FILE: ../../../flutter/fml/raster_thread_merger.cc
 FILE: ../../../flutter/fml/raster_thread_merger.h
@@ -294,6 +296,9 @@ FILE: ../../../flutter/fml/shared_thread_merger.cc
 FILE: ../../../flutter/fml/shared_thread_merger.h
 FILE: ../../../flutter/fml/size.h
 FILE: ../../../flutter/fml/status.h
+FILE: ../../../flutter/fml/string_conversion.cc
+FILE: ../../../flutter/fml/string_conversion.h
+FILE: ../../../flutter/fml/string_conversion_unittests.cc
 FILE: ../../../flutter/fml/synchronization/atomic_object.h
 FILE: ../../../flutter/fml/synchronization/count_down_latch.cc
 FILE: ../../../flutter/fml/synchronization/count_down_latch.h
@@ -2049,9 +2054,6 @@ FILE: ../../../flutter/shell/platform/windows/public/flutter_windows.h
 FILE: ../../../flutter/shell/platform/windows/sequential_id_generator.cc
 FILE: ../../../flutter/shell/platform/windows/sequential_id_generator.h
 FILE: ../../../flutter/shell/platform/windows/sequential_id_generator_unittests.cc
-FILE: ../../../flutter/shell/platform/windows/string_conversion.cc
-FILE: ../../../flutter/shell/platform/windows/string_conversion.h
-FILE: ../../../flutter/shell/platform/windows/string_conversion_unittests.cc
 FILE: ../../../flutter/shell/platform/windows/system_utils.h
 FILE: ../../../flutter/shell/platform/windows/system_utils_unittests.cc
 FILE: ../../../flutter/shell/platform/windows/system_utils_win32.cc
diff --git a/fml/BUILD.gn b/fml/BUILD.gn
index 39610f6aa5613..71f3f929a542b 100644
--- a/fml/BUILD.gn
+++ b/fml/BUILD.gn
@@ -104,7 +104,11 @@ source_set("fml") {
     sources += [ "backtrace_stub.cc" ]
   }
 
-  public_deps = [ ":command_line" ]
+  public_deps = [
+    ":build_config",
+    ":command_line",
+    ":string_conversion",
+  ]
 
   deps = [
     "//third_party/abseil-cpp/absl/debugging:symbolize",
@@ -217,11 +221,7 @@ source_set("fml") {
       "platform/win/native_library_win.cc",
       "platform/win/paths_win.cc",
       "platform/win/posix_wrappers_win.cc",
-      "platform/win/wstring_conversion.h",
     ]
-
-    # For wstring_conversion. See issue #50053.
-    defines = [ "_SILENCE_CXX17_CODECVT_HEADER_DEPRECATION_WARNING" ]
   } else {
     sources += [
       "platform/posix/file_posix.cc",
@@ -233,6 +233,15 @@ source_set("fml") {
   }
 }
 
+source_set("build_config") {
+  sources = [ "build_config.h" ]
+
+  public_configs = [
+    "//flutter:config",
+    "//flutter/common:flutter_config",
+  ]
+}
+
 source_set("command_line") {
   sources = [
     "command_line.cc",
@@ -245,6 +254,30 @@ source_set("command_line") {
   ]
 }
 
+source_set("string_conversion") {
+  sources = [
+    "string_conversion.cc",
+    "string_conversion.h",
+  ]
+
+  if (is_win) {
+    sources += [
+      "platform/win/wstring_conversion.cc",
+      "platform/win/wstring_conversion.h",
+    ]
+
+    # TODO(cbracken): https://github.com/flutter/flutter/issues/50053
+    defines = [ "_SILENCE_CXX17_CODECVT_HEADER_DEPRECATION_WARNING" ]
+  }
+
+  deps = [ ":build_config" ]
+
+  public_configs = [
+    "//flutter:config",
+    "//flutter/common:flutter_config",
+  ]
+}
+
 if (enable_unittests) {
   test_fixtures("fml_fixtures") {
     fixtures = []
@@ -286,6 +319,7 @@ if (enable_unittests) {
       "message_loop_unittests.cc",
       "paths_unittests.cc",
       "raster_thread_merger_unittests.cc",
+      "string_conversion_unittests.cc",
       "synchronization/count_down_latch_unittests.cc",
       "synchronization/semaphore_unittest.cc",
       "synchronization/sync_switch_unittest.cc",
@@ -307,6 +341,10 @@ if (enable_unittests) {
       ]
     }
 
+    if (is_win) {
+      sources += [ "platform/win/wstring_conversion_unittests.cc" ]
+    }
+
     deps = [
       ":fml_fixtures",
       "//flutter/fml",
diff --git a/fml/platform/win/errors_win.cc b/fml/platform/win/errors_win.cc
index 7370ee86ff425..35f5b0add6843 100644
--- a/fml/platform/win/errors_win.cc
+++ b/fml/platform/win/errors_win.cc
@@ -40,7 +40,7 @@ std::string GetLastErrorMessage() {
   std::wstringstream stream;
   stream << message << " (" << last_error << ").";
 
-  return WideStringToString(stream.str());
+  return WideStringToUtf8(stream.str());
 }
 
 }  // namespace fml
diff --git a/fml/platform/win/file_win.cc b/fml/platform/win/file_win.cc
index c5a3eb1775daa..9f60ea59d86d3 100644
--- a/fml/platform/win/file_win.cc
+++ b/fml/platform/win/file_win.cc
@@ -45,7 +45,7 @@ static std::string GetFullHandlePath(const fml::UniqueFD& handle) {
     // was cached
     if (result && memcmp(found.value().id.Identifier, info.FileId.Identifier,
                          sizeof(FILE_ID_INFO))) {
-      return WideStringToString(found.value().filename);
+      return WideStringToUtf8(found.value().filename);
     } else {
       fml::internal::os_win::UniqueFDTraits::RemoveCacheEntry(handle.get());
     }
@@ -59,7 +59,7 @@ static std::string GetFullHandlePath(const fml::UniqueFD& handle) {
   if (buffer_size == 0) {
     return {};
   }
-  return WideStringToString({buffer, buffer_size});
+  return WideStringToUtf8({buffer, buffer_size});
 #endif
 }
 
@@ -106,7 +106,7 @@ static DWORD GetShareFlags(FilePermission permission) {
 }
 
 static DWORD GetFileAttributesForUtf8Path(const char* absolute_path) {
-  return ::GetFileAttributes(StringToWideString(absolute_path).c_str());
+  return ::GetFileAttributes(Utf8ToWideString(absolute_path).c_str());
 }
 
 static DWORD GetFileAttributesForUtf8Path(const fml::UniqueFD& base_directory,
@@ -147,7 +147,7 @@ std::string CreateTemporaryDirectory() {
   stream << temp_dir_container << "\\" << uuid_str;
   auto temp_dir = stream.str();
 
-  auto dir_fd = OpenDirectory(WideStringToString(temp_dir).c_str(), true,
+  auto dir_fd = OpenDirectory(WideStringToUtf8(temp_dir).c_str(), true,
                               FilePermission::kReadWrite);
   if (!dir_fd.is_valid()) {
     FML_DLOG(ERROR) << "Could not get temporary directory file descriptor. "
@@ -155,7 +155,7 @@ std::string CreateTemporaryDirectory() {
     return {};
   }
 
-  return WideStringToString(std::move(temp_dir));
+  return WideStringToUtf8(std::move(temp_dir));
 }
 
 fml::UniqueFD OpenFile(const fml::UniqueFD& base_directory,
@@ -173,7 +173,7 @@ fml::UniqueFD OpenFile(const char* path,
     return {};
   }
 
-  auto file_name = StringToWideString({path});
+  auto file_name = Utf8ToWideString({path});
 
   if (file_name.size() == 0) {
     return {};
@@ -216,7 +216,7 @@ fml::UniqueFD OpenDirectory(const char* path,
     return {};
   }
 
-  auto file_name = StringToWideString({path});
+  auto file_name = Utf8ToWideString({path});
 
   if (file_name.size() == 0) {
     return {};
@@ -314,7 +314,7 @@ bool IsFile(const std::string& path) {
 }
 
 bool UnlinkDirectory(const char* path) {
-  if (!::RemoveDirectory(StringToWideString(path).c_str())) {
+  if (!::RemoveDirectory(Utf8ToWideString(path).c_str())) {
     FML_DLOG(ERROR) << "Could not remove directory: '" << path << "'. "
                     << GetLastErrorMessage();
     return false;
@@ -324,7 +324,7 @@ bool UnlinkDirectory(const char* path) {
 
 bool UnlinkDirectory(const fml::UniqueFD& base_directory, const char* path) {
   if (!::RemoveDirectory(
-          StringToWideString(GetAbsolutePath(base_directory, path)).c_str())) {
+          Utf8ToWideString(GetAbsolutePath(base_directory, path)).c_str())) {
     FML_DLOG(ERROR) << "Could not remove directory: '" << path << "'. "
                     << GetLastErrorMessage();
     return false;
@@ -333,7 +333,7 @@ bool UnlinkDirectory(const fml::UniqueFD& base_directory, const char* path) {
 }
 
 bool UnlinkFile(const char* path) {
-  if (!::DeleteFile(StringToWideString(path).c_str())) {
+  if (!::DeleteFile(Utf8ToWideString(path).c_str())) {
     FML_DLOG(ERROR) << "Could not remove file: '" << path << "'. "
                     << GetLastErrorMessage();
     return false;
@@ -343,7 +343,7 @@ bool UnlinkFile(const char* path) {
 
 bool UnlinkFile(const fml::UniqueFD& base_directory, const char* path) {
   if (!::DeleteFile(
-          StringToWideString(GetAbsolutePath(base_directory, path)).c_str())) {
+          Utf8ToWideString(GetAbsolutePath(base_directory, path)).c_str())) {
     FML_DLOG(ERROR) << "Could not remove file: '" << path << "'. "
                     << GetLastErrorMessage();
     return false;
@@ -436,8 +436,8 @@ bool WriteAtomically(const fml::UniqueFD& base_directory,
 
   temp_file.reset();
 
-  if (!::MoveFile(StringToWideString(temp_file_path).c_str(),
-                  StringToWideString(file_path).c_str())) {
+  if (!::MoveFile(Utf8ToWideString(temp_file_path).c_str(),
+                  Utf8ToWideString(file_path).c_str())) {
     FML_DLOG(ERROR)
         << "Could not replace temp file at correct path. File path: "
         << file_path << ". Temp file path: " << temp_file_path << " "
@@ -451,8 +451,8 @@ bool WriteAtomically(const fml::UniqueFD& base_directory,
 bool VisitFiles(const fml::UniqueFD& directory, const FileVisitor& visitor) {
   std::string search_pattern = GetFullHandlePath(directory) + "\\*";
   WIN32_FIND_DATA find_file_data;
-  HANDLE find_handle = ::FindFirstFile(
-      StringToWideString(search_pattern).c_str(), &find_file_data);
+  HANDLE find_handle = ::FindFirstFile(Utf8ToWideString(search_pattern).c_str(),
+                                       &find_file_data);
 
   if (find_handle == INVALID_HANDLE_VALUE) {
     FML_DLOG(ERROR) << "Can't open the directory. Error: "
@@ -461,7 +461,7 @@ bool VisitFiles(const fml::UniqueFD& directory, const FileVisitor& visitor) {
   }
 
   do {
-    std::string filename = WideStringToString(find_file_data.cFileName);
+    std::string filename = WideStringToUtf8(find_file_data.cFileName);
     if (filename != "." && filename != "..") {
       if (!visitor(directory, filename)) {
         ::FindClose(find_handle);
diff --git a/fml/platform/win/native_library_win.cc b/fml/platform/win/native_library_win.cc
index 27a880066110f..6c1bf5c94e098 100644
--- a/fml/platform/win/native_library_win.cc
+++ b/fml/platform/win/native_library_win.cc
@@ -16,7 +16,7 @@ NativeLibrary::NativeLibrary(const char* path)
     return;
   }
 
-  handle_ = ::LoadLibrary(StringToWideString(path).c_str());
+  handle_ = ::LoadLibrary(Utf8ToWideString(path).c_str());
 }
 
 NativeLibrary::NativeLibrary(Handle handle, bool close_handle)
diff --git a/fml/platform/win/wstring_conversion.cc b/fml/platform/win/wstring_conversion.cc
new file mode 100644
index 0000000000000..6e4e36e8cf629
--- /dev/null
+++ b/fml/platform/win/wstring_conversion.cc
@@ -0,0 +1,26 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/fml/platform/win/wstring_conversion.h"
+
+#include <codecvt>
+#include <locale>
+#include <string>
+
+namespace fml {
+
+using WideStringConverter =
+    std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t>;
+
+std::string WideStringToUtf8(const std::wstring_view str) {
+  WideStringConverter converter;
+  return converter.to_bytes(str.data());
+}
+
+std::wstring Utf8ToWideString(const std::string_view str) {
+  WideStringConverter converter;
+  return converter.from_bytes(str.data());
+}
+
+}  // namespace fml
diff --git a/fml/platform/win/wstring_conversion.h b/fml/platform/win/wstring_conversion.h
index d68f6156730b0..4e7c110685491 100644
--- a/fml/platform/win/wstring_conversion.h
+++ b/fml/platform/win/wstring_conversion.h
@@ -5,24 +5,16 @@
 #ifndef FLUTTER_FML_PLATFORM_WIN_WSTRING_CONVERSION_H_
 #define FLUTTER_FML_PLATFORM_WIN_WSTRING_CONVERSION_H_
 
-#include <codecvt>
-#include <locale>
 #include <string>
 
 namespace fml {
 
-using WideStringConvertor =
-    std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t>;
+// Returns a UTF-8 encoded equivalent of a UTF-16 encoded input wide string.
+std::string WideStringToUtf8(const std::wstring_view str);
 
-inline std::wstring StringToWideString(const std::string& str) {
-  WideStringConvertor converter;
-  return converter.from_bytes(str);
-}
-
-inline std::string WideStringToString(const std::wstring& wstr) {
-  WideStringConvertor converter;
-  return converter.to_bytes(wstr);
-}
+// Returns a UTF-16 encoded wide string equivalent of a UTF-8 encoded input
+// string.
+std::wstring Utf8ToWideString(const std::string_view str);
 
 }  // namespace fml
 
diff --git a/fml/platform/win/wstring_conversion_unittests.cc b/fml/platform/win/wstring_conversion_unittests.cc
new file mode 100644
index 0000000000000..81af2594ce94c
--- /dev/null
+++ b/fml/platform/win/wstring_conversion_unittests.cc
@@ -0,0 +1,37 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/fml/platform/win/wstring_conversion.h"
+
+#include "gtest/gtest.h"
+
+namespace fml {
+namespace testing {
+
+TEST(StringConversion, Utf16ToWideStringEmpty) {
+  EXPECT_EQ(Utf8ToWideString(""), L"");
+}
+
+TEST(StringConversion, Utf8ToWideStringAscii) {
+  EXPECT_EQ(Utf8ToWideString("abc123"), L"abc123");
+}
+
+TEST(StringConversion, Utf8ToWideStringUnicode) {
+  EXPECT_EQ(Utf8ToWideString("\xe2\x98\x83"), L"\x2603");
+}
+
+TEST(StringConversion, WideStringToUtf8Empty) {
+  EXPECT_EQ(WideStringToUtf8(L""), "");
+}
+
+TEST(StringConversion, WideStringToUtf8Ascii) {
+  EXPECT_EQ(WideStringToUtf8(L"abc123"), "abc123");
+}
+
+TEST(StringConversion, WideStringToUtf8Unicode) {
+  EXPECT_EQ(WideStringToUtf8(L"\x2603"), "\xe2\x98\x83");
+}
+
+}  // namespace testing
+}  // namespace fml
diff --git a/fml/string_conversion.cc b/fml/string_conversion.cc
new file mode 100644
index 0000000000000..7b718fef19394
--- /dev/null
+++ b/fml/string_conversion.cc
@@ -0,0 +1,35 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/fml/string_conversion.h"
+
+#include <codecvt>
+#include <locale>
+#include <string>
+
+#include "flutter/fml/build_config.h"
+
+#if defined(FML_OS_WIN)
+// TODO(naifu): https://github.com/flutter/flutter/issues/98074
+// Eliminate this workaround for a link error on Windows when the underlying
+// bug is fixed.
+std::locale::id std::codecvt<char16_t, char, _Mbstatet>::id;
+#endif  // defined(FML_OS_WIN)
+
+namespace fml {
+
+using Utf16StringConverter =
+    std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>;
+
+std::string Utf16ToUtf8(const std::u16string_view string) {
+  Utf16StringConverter converter;
+  return converter.to_bytes(string.data());
+}
+
+std::u16string Utf8ToUtf16(const std::string_view string) {
+  Utf16StringConverter converter;
+  return converter.from_bytes(string.data());
+}
+
+}  // namespace fml
diff --git a/fml/string_conversion.h b/fml/string_conversion.h
new file mode 100644
index 0000000000000..5c2402980dab5
--- /dev/null
+++ b/fml/string_conversion.h
@@ -0,0 +1,20 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_FML_STRING_CONVERSION_H_
+#define FLUTTER_FML_STRING_CONVERSION_H_
+
+#include <string>
+
+namespace fml {
+
+// Returns a UTF-8 encoded equivalent of a UTF-16 encoded input string.
+std::string Utf16ToUtf8(const std::u16string_view string);
+
+// Returns a UTF-16 encoded equivalent of a UTF-8 encoded input string.
+std::u16string Utf8ToUtf16(const std::string_view string);
+
+}  // namespace fml
+
+#endif  // FLUTTER_FML_STRING_CONVERSION_H_
diff --git a/fml/string_conversion_unittests.cc b/fml/string_conversion_unittests.cc
new file mode 100644
index 0000000000000..4d12075709014
--- /dev/null
+++ b/fml/string_conversion_unittests.cc
@@ -0,0 +1,37 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/fml/string_conversion.h"
+
+#include "gtest/gtest.h"
+
+namespace fml {
+namespace testing {
+
+TEST(StringConversion, Utf16ToUtf16Empty) {
+  EXPECT_EQ(Utf8ToUtf16(""), u"");
+}
+
+TEST(StringConversion, Utf8ToUtf16Ascii) {
+  EXPECT_EQ(Utf8ToUtf16("abc123"), u"abc123");
+}
+
+TEST(StringConversion, Utf8ToUtf16Unicode) {
+  EXPECT_EQ(Utf8ToUtf16("\xe2\x98\x83"), u"\x2603");
+}
+
+TEST(StringConversion, Utf16ToUtf8Empty) {
+  EXPECT_EQ(Utf16ToUtf8(u""), "");
+}
+
+TEST(StringConversion, Utf16ToUtf8Ascii) {
+  EXPECT_EQ(Utf16ToUtf8(u"abc123"), "abc123");
+}
+
+TEST(StringConversion, Utf16ToUtf8Unicode) {
+  EXPECT_EQ(Utf16ToUtf8(u"\x2603"), "\xe2\x98\x83");
+}
+
+}  // namespace testing
+}  // namespace fml
diff --git a/shell/platform/common/BUILD.gn b/shell/platform/common/BUILD.gn
index 1125ee35553ce..0f0136d2320ea 100644
--- a/shell/platform/common/BUILD.gn
+++ b/shell/platform/common/BUILD.gn
@@ -54,11 +54,6 @@ source_set("common_cpp_input") {
   public_configs = [ "//flutter:config" ]
 
   deps = [ "//flutter/fml:fml" ]
-
-  if (is_win) {
-    # For wstring_conversion. See issue #50053.
-    defines = [ "_SILENCE_CXX17_CODECVT_HEADER_DEPRECATION_WARNING" ]
-  }
 }
 
 source_set("common_cpp_switches") {
@@ -181,6 +176,7 @@ if (enable_unittests) {
       ":common_cpp_fixtures",
       ":common_cpp_input",
       ":common_cpp_switches",
+      "//flutter/fml:string_conversion",
       "//flutter/shell/platform/common/client_wrapper:client_wrapper",
       "//flutter/shell/platform/common/client_wrapper:client_wrapper_library_stubs",
       "//flutter/testing",
diff --git a/shell/platform/common/text_editing_delta.cc b/shell/platform/common/text_editing_delta.cc
index e07cdcb30a1b6..2c89a2cd5ef31 100644
--- a/shell/platform/common/text_editing_delta.cc
+++ b/shell/platform/common/text_editing_delta.cc
@@ -4,6 +4,8 @@
 
 #include "flutter/shell/platform/common/text_editing_delta.h"
 
+#include "flutter/fml/string_conversion.h"
+
 namespace flutter {
 
 TextEditingDelta::TextEditingDelta(const std::u16string& text_before_change,
@@ -17,8 +19,8 @@ TextEditingDelta::TextEditingDelta(const std::u16string& text_before_change,
 TextEditingDelta::TextEditingDelta(const std::string& text_before_change,
                                    TextRange range,
                                    const std::string& text)
-    : old_text_(Utf8ToUtf16(text_before_change)),
-      delta_text_(Utf8ToUtf16(text)),
+    : old_text_(fml::Utf8ToUtf16(text_before_change)),
+      delta_text_(fml::Utf8ToUtf16(text)),
       delta_start_(range.start()),
       delta_end_(range.start() + range.length()) {}
 
@@ -26,7 +28,7 @@ TextEditingDelta::TextEditingDelta(const std::u16string& text)
     : old_text_(text), delta_text_(u""), delta_start_(-1), delta_end_(-1) {}
 
 TextEditingDelta::TextEditingDelta(const std::string& text)
-    : old_text_(Utf8ToUtf16(text)),
+    : old_text_(fml::Utf8ToUtf16(text)),
       delta_text_(u""),
       delta_start_(-1),
       delta_end_(-1) {}
diff --git a/shell/platform/common/text_editing_delta.h b/shell/platform/common/text_editing_delta.h
index e66e891f7db18..528277b67306f 100644
--- a/shell/platform/common/text_editing_delta.h
+++ b/shell/platform/common/text_editing_delta.h
@@ -4,11 +4,10 @@
 
 #ifndef FLUTTER_SHELL_PLATFORM_COMMON_TEXT_EDITING_DELTA_H_
 #define FLUTTER_SHELL_PLATFORM_COMMON_TEXT_EDITING_DELTA_H_
-#define _SILENCE_CXX17_CODECVT_HEADER_DEPRECATION_WARNING
 
-#include <codecvt>
 #include <string>
 
+#include "flutter/fml/string_conversion.h"
 #include "flutter/shell/platform/common/text_range.h"
 
 namespace flutter {
@@ -32,12 +31,12 @@ struct TextEditingDelta {
   /// Get the old_text_ value.
   ///
   /// All strings are stored as UTF16 but converted to UTF8 when accessed.
-  std::string old_text() const { return Utf16ToUtf8(old_text_); }
+  std::string old_text() const { return fml::Utf16ToUtf8(old_text_); }
 
   /// Get the delta_text value.
   ///
   /// All strings are stored as UTF16 but converted to UTF8 when accessed.
-  std::string delta_text() const { return Utf16ToUtf8(delta_text_); }
+  std::string delta_text() const { return fml::Utf16ToUtf8(delta_text_); }
 
   /// Get the delta_start_ value.
   int delta_start() const { return delta_start_; }
@@ -71,20 +70,6 @@ struct TextEditingDelta {
   void set_delta_start(int delta_start) { delta_start_ = delta_start; }
 
   void set_delta_end(int delta_end) { delta_end_ = delta_end; }
-
-  // Given a UTF16-encoded string, returns the string encoded in UTF8.
-  static std::string Utf16ToUtf8(const std::u16string& string) {
-    std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>
-        utf8_converter;
-    return utf8_converter.to_bytes(string);
-  }
-
-  // Given a UTF8-encoded string, returns the string encoded in UTF16.
-  static std::u16string Utf8ToUtf16(const std::string& string) {
-    std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>
-        utf16_converter;
-    return utf16_converter.from_bytes(string);
-  }
 };
 
 }  // namespace flutter
diff --git a/shell/platform/common/text_input_model.cc b/shell/platform/common/text_input_model.cc
index d6354650b2f72..93f297df91840 100644
--- a/shell/platform/common/text_input_model.cc
+++ b/shell/platform/common/text_input_model.cc
@@ -5,14 +5,9 @@
 #include "flutter/shell/platform/common/text_input_model.h"
 
 #include <algorithm>
-#include <codecvt>
-#include <locale>
+#include <string>
 
-#if defined(_MSC_VER)
-// TODO(naifu): This temporary code is to solve link error.(VS2015/2017)
-// https://social.msdn.microsoft.com/Forums/vstudio/en-US/8f40dcd8-c67f-4eba-9134-a19b9178e481/vs-2015-rc-linker-stdcodecvt-error
-std::locale::id std::codecvt<char16_t, char, _Mbstatet>::id;
-#endif  // defined(_MSC_VER)
+#include "flutter/fml/string_conversion.h"
 
 namespace flutter {
 
@@ -34,9 +29,7 @@ TextInputModel::TextInputModel() = default;
 TextInputModel::~TextInputModel() = default;
 
 void TextInputModel::SetText(const std::string& text) {
-  std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>
-      utf16_converter;
-  text_ = utf16_converter.from_bytes(text);
+  text_ = fml::Utf8ToUtf16(text);
   selection_ = TextRange(0);
   composing_range_ = TextRange(0);
 }
@@ -79,9 +72,7 @@ void TextInputModel::UpdateComposingText(const std::u16string& text) {
 }
 
 void TextInputModel::UpdateComposingText(const std::string& text) {
-  std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>
-      utf16_converter;
-  UpdateComposingText(utf16_converter.from_bytes(text));
+  UpdateComposingText(fml::Utf8ToUtf16(text));
 }
 
 void TextInputModel::CommitComposing() {
@@ -140,9 +131,7 @@ void TextInputModel::AddText(const std::u16string& text) {
 }
 
 void TextInputModel::AddText(const std::string& text) {
-  std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>
-      utf16_converter;
-  AddText(utf16_converter.from_bytes(text));
+  AddText(fml::Utf8ToUtf16(text));
 }
 
 bool TextInputModel::Backspace() {
@@ -290,18 +279,14 @@ bool TextInputModel::MoveCursorBack() {
 }
 
 std::string TextInputModel::GetText() const {
-  std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>
-      utf8_converter;
-  return utf8_converter.to_bytes(text_);
+  return fml::Utf16ToUtf8(text_);
 }
 
 int TextInputModel::GetCursorOffset() const {
   // Measure the length of the current text up to the selection extent.
   // There is probably a much more efficient way of doing this.
   auto leading_text = text_.substr(0, selection_.extent());
-  std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>
-      utf8_converter;
-  return utf8_converter.to_bytes(leading_text).size();
+  return fml::Utf16ToUtf8(leading_text).size();
 }
 
 }  // namespace flutter
diff --git a/shell/platform/windows/BUILD.gn b/shell/platform/windows/BUILD.gn
index a19418e2aa75d..ee8504033e701 100644
--- a/shell/platform/windows/BUILD.gn
+++ b/shell/platform/windows/BUILD.gn
@@ -165,7 +165,7 @@ source_set("flutter_windows_source") {
   }
 
   public_deps = [
-    ":string_conversion",
+    "//flutter/fml:string_conversion",
     "//flutter/shell/platform/common:common_cpp_accessibility",
   ]
 
@@ -187,18 +187,6 @@ source_set("flutter_windows_source") {
   ]
 }
 
-# String encoding conversion utilities.
-source_set("string_conversion") {
-  sources = [
-    "string_conversion.cc",
-    "string_conversion.h",
-  ]
-
-  if (target_os == "winuwp") {
-    cflags = [ "/EHsc" ]
-  }
-}
-
 copy("publish_headers_windows") {
   sources = _public_headers
   outputs = [ "$root_out_dir/{{source_file_part}}" ]
@@ -238,7 +226,6 @@ executable("flutter_windows_unittests") {
     # "flutter_project_bundle_unittests.cc", //TODO failing due to switches test failing.  Blocked on https://github.com/flutter/flutter/issues/74153
     # "flutter_windows_engine_unittests.cc", //TODO failing to send / receive platform message get plugins working first.  Blocked on https://github.com/flutter/flutter/issues/74155
     "sequential_id_generator_unittests.cc",
-    "string_conversion_unittests.cc",
     "system_utils_unittests.cc",
     "task_runner_unittests.cc",
     "testing/engine_modifier.h",
@@ -352,7 +339,7 @@ source_set("uwptool_utils") {
     "uwptool_utils.h",
   ]
 
-  deps = [ ":string_conversion" ]
+  deps = [ "//flutter/fml:string_conversion" ]
 
   defines = [ "_SILENCE_CLANG_COROUTINE_MESSAGE" ]
 }
@@ -372,9 +359,9 @@ executable("uwptool") {
 
   sources = [ "uwptool_main.cc" ]
   deps = [
-    ":string_conversion",
     ":uwptool_utils",
     "//flutter/fml:command_line",
+    "//flutter/fml:string_conversion",
   ]
 
   defines = [ "_SILENCE_CLANG_COROUTINE_MESSAGE" ]
diff --git a/shell/platform/windows/flutter_windows_engine.cc b/shell/platform/windows/flutter_windows_engine.cc
index 418c1b5baf7bf..ec4a556f7098b 100644
--- a/shell/platform/windows/flutter_windows_engine.cc
+++ b/shell/platform/windows/flutter_windows_engine.cc
@@ -8,12 +8,12 @@
 #include <iostream>
 #include <sstream>
 
+#include "flutter/fml/platform/win/wstring_conversion.h"
 #include "flutter/shell/platform/common/client_wrapper/binary_messenger_impl.h"
 #include "flutter/shell/platform/common/client_wrapper/include/flutter/basic_message_channel.h"
 #include "flutter/shell/platform/common/json_message_codec.h"
 #include "flutter/shell/platform/common/path_utils.h"
 #include "flutter/shell/platform/windows/flutter_windows_view.h"
-#include "flutter/shell/platform/windows/string_conversion.h"
 #include "flutter/shell/platform/windows/system_utils.h"
 #include "flutter/shell/platform/windows/task_runner.h"
 #include "third_party/rapidjson/include/rapidjson/document.h"
@@ -448,7 +448,8 @@ void FlutterWindowsEngine::SendSystemSettings() {
                      Prefer24HourTime(GetUserTimeFormat()), allocator);
   settings.AddMember("textScaleFactor", 1.0, allocator);
   settings.AddMember("platformBrightness",
-                     Utf8FromUtf16(GetPreferredBrightness()), allocator);
+                     fml::WideStringToUtf8(GetPreferredBrightness()),
+                     allocator);
   settings_channel_->Send(settings);
 }
 
diff --git a/shell/platform/windows/keyboard_key_embedder_handler.cc b/shell/platform/windows/keyboard_key_embedder_handler.cc
index bc4632877e963..ca8e5a9cdadfd 100644
--- a/shell/platform/windows/keyboard_key_embedder_handler.cc
+++ b/shell/platform/windows/keyboard_key_embedder_handler.cc
@@ -8,12 +8,10 @@
 #include <windows.h>
 
 #include <chrono>
-#include <codecvt>
 #include <iostream>
 #include <string>
 
 #include "flutter/shell/platform/windows/keyboard_win32_common.h"
-#include "flutter/shell/platform/windows/string_conversion.h"
 
 namespace flutter {
 
diff --git a/shell/platform/windows/platform_handler_win32.cc b/shell/platform/windows/platform_handler_win32.cc
index 1985f85ed27b5..9e73e431ddbd1 100644
--- a/shell/platform/windows/platform_handler_win32.cc
+++ b/shell/platform/windows/platform_handler_win32.cc
@@ -10,8 +10,8 @@
 #include <iostream>
 #include <optional>
 
+#include "flutter/fml/platform/win/wstring_conversion.h"
 #include "flutter/shell/platform/windows/flutter_windows_view.h"
-#include "flutter/shell/platform/windows/string_conversion.h"
 
 static constexpr char kValueKey[] = "value";
 
@@ -227,7 +227,8 @@ void PlatformHandlerWin32::GetPlainText(
   rapidjson::Document::AllocatorType& allocator = document.GetAllocator();
   document.AddMember(
       rapidjson::Value(key.data(), allocator),
-      rapidjson::Value(Utf8FromUtf16(*clipboard_string), allocator), allocator);
+      rapidjson::Value(fml::WideStringToUtf8(*clipboard_string), allocator),
+      allocator);
   result->Success(document);
 }
 
@@ -259,7 +260,7 @@ void PlatformHandlerWin32::SetPlainText(
     result->Error(kClipboardError, "Unable to open clipboard", error_code);
     return;
   }
-  if (!clipboard.SetString(Utf16FromUtf8(text))) {
+  if (!clipboard.SetString(fml::Utf8ToWideString(text))) {
     rapidjson::Document error_code;
     error_code.SetInt(::GetLastError());
     result->Error(kClipboardError, "Unable to set clipboard data", error_code);
diff --git a/shell/platform/windows/platform_handler_winuwp.cc b/shell/platform/windows/platform_handler_winuwp.cc
index f0bc19d0f1efe..3134727847fed 100644
--- a/shell/platform/windows/platform_handler_winuwp.cc
+++ b/shell/platform/windows/platform_handler_winuwp.cc
@@ -8,8 +8,8 @@
 #include "third_party/cppwinrt/generated/winrt/Windows.Foundation.h"
 #include "third_party/cppwinrt/generated/winrt/Windows.UI.Core.h"
 
+#include "flutter/fml/platform/win/wstring_conversion.h"
 #include "flutter/shell/platform/windows/flutter_windows_view.h"
-#include "flutter/shell/platform/windows/string_conversion.h"
 
 static constexpr char kValueKey[] = "value";
 
@@ -61,19 +61,19 @@ void PlatformHandlerWinUwp::GetPlainText(
   // Waiting `DataPackageView::GetTextAsync()` using `TResult.get()` on the
   // platform thread will causes the application stop, so we continue
   // response on this callback.
-  content.GetTextAsync().Completed(
-      [result = std::move(result), key](auto async_info, auto _async_status) {
-        auto clipboard_string = async_info.GetResults();
-
-        rapidjson::Document document;
-        document.SetObject();
-        rapidjson::Document::AllocatorType& allocator = document.GetAllocator();
-        document.AddMember(
-            rapidjson::Value(key.data(), allocator),
-            rapidjson::Value(Utf8FromUtf16(clipboard_string), allocator),
-            allocator);
-        result->Success(document);
-      });
+  content.GetTextAsync().Completed([result = std::move(result), key](
+                                       auto async_info, auto _async_status) {
+    auto clipboard_string = async_info.GetResults();
+
+    rapidjson::Document document;
+    document.SetObject();
+    rapidjson::Document::AllocatorType& allocator = document.GetAllocator();
+    document.AddMember(
+        rapidjson::Value(key.data(), allocator),
+        rapidjson::Value(fml::WideStringToUtf8(clipboard_string), allocator),
+        allocator);
+    result->Success(document);
+  });
 }
 
 void PlatformHandlerWinUwp::GetHasStrings(
@@ -101,7 +101,7 @@ void PlatformHandlerWinUwp::SetPlainText(
     const std::string& text,
     std::unique_ptr<MethodResult<rapidjson::Document>> result) {
   winrt::Windows::ApplicationModel::DataTransfer::DataPackage content;
-  content.SetText(Utf16FromUtf8(text));
+  content.SetText(fml::Utf8ToWideString(text));
   winrt::Windows::ApplicationModel::DataTransfer::Clipboard::SetContent(
       content);
 
diff --git a/shell/platform/windows/string_conversion.cc b/shell/platform/windows/string_conversion.cc
deleted file mode 100644
index d3ab3143ea7f6..0000000000000
--- a/shell/platform/windows/string_conversion.cc
+++ /dev/null
@@ -1,55 +0,0 @@
-// Copyright 2013 The Flutter Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "flutter/shell/platform/windows/string_conversion.h"
-
-#include <Windows.h>
-
-namespace flutter {
-
-std::string Utf8FromUtf16(const std::wstring_view utf16_string) {
-  if (utf16_string.empty()) {
-    return std::string();
-  }
-  int target_length = ::WideCharToMultiByte(
-      CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string.data(),
-      static_cast<int>(utf16_string.length()), nullptr, 0, nullptr, nullptr);
-  if (target_length == 0) {
-    return std::string();
-  }
-  std::string utf8_string;
-  utf8_string.resize(target_length);
-  int converted_length = ::WideCharToMultiByte(
-      CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string.data(),
-      static_cast<int>(utf16_string.length()), utf8_string.data(),
-      target_length, nullptr, nullptr);
-  if (converted_length == 0) {
-    return std::string();
-  }
-  return utf8_string;
-}
-
-std::wstring Utf16FromUtf8(const std::string_view utf8_string) {
-  if (utf8_string.empty()) {
-    return std::wstring();
-  }
-  int target_length =
-      ::MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, utf8_string.data(),
-                            static_cast<int>(utf8_string.length()), nullptr, 0);
-  if (target_length == 0) {
-    return std::wstring();
-  }
-  std::wstring utf16_string;
-  utf16_string.resize(target_length);
-  int converted_length =
-      ::MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, utf8_string.data(),
-                            static_cast<int>(utf8_string.length()),
-                            utf16_string.data(), target_length);
-  if (converted_length == 0) {
-    return std::wstring();
-  }
-  return utf16_string;
-}
-
-}  // namespace flutter
diff --git a/shell/platform/windows/string_conversion.h b/shell/platform/windows/string_conversion.h
deleted file mode 100644
index b79aed4711072..0000000000000
--- a/shell/platform/windows/string_conversion.h
+++ /dev/null
@@ -1,22 +0,0 @@
-// Copyright 2013 The Flutter Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef FLUTTER_SHELL_PLATFORM_WINDOWS_STRING_CONVERSION_H_
-#define FLUTTER_SHELL_PLATFORM_WINDOWS_STRING_CONVERSION_H_
-
-#include <string>
-
-namespace flutter {
-
-// Converts a string from UTF-16 to UTF-8. Returns an empty string if the
-// input is not valid UTF-16.
-std::string Utf8FromUtf16(const std::wstring_view utf16_string);
-
-// Converts a string from UTF-8 to UTF-16. Returns an empty string if the
-// input is not valid UTF-8.
-std::wstring Utf16FromUtf8(const std::string_view utf8_string);
-
-}  // namespace flutter
-
-#endif  // FLUTTER_SHELL_PLATFORM_WINDOWS_STRING_CONVERSION_H_
diff --git a/shell/platform/windows/string_conversion_unittests.cc b/shell/platform/windows/string_conversion_unittests.cc
deleted file mode 100644
index aa8dc967f3c81..0000000000000
--- a/shell/platform/windows/string_conversion_unittests.cc
+++ /dev/null
@@ -1,37 +0,0 @@
-// Copyright 2013 The Flutter Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "flutter/shell/platform/windows/string_conversion.h"
-
-#include "gtest/gtest.h"
-
-namespace flutter {
-namespace testing {
-
-TEST(StringConversion, Utf16FromUtf8Empty) {
-  EXPECT_EQ(Utf16FromUtf8(""), L"");
-}
-
-TEST(StringConversion, Utf16FromUtf8Ascii) {
-  EXPECT_EQ(Utf16FromUtf8("abc123"), L"abc123");
-}
-
-TEST(StringConversion, Utf16FromUtf8Unicode) {
-  EXPECT_EQ(Utf16FromUtf8("\xe2\x98\x83"), L"\x2603");
-}
-
-TEST(StringConversion, Utf8FromUtf16Empty) {
-  EXPECT_EQ(Utf8FromUtf16(L""), "");
-}
-
-TEST(StringConversion, Utf8FromUtf16Ascii) {
-  EXPECT_EQ(Utf8FromUtf16(L"abc123"), "abc123");
-}
-
-TEST(StringConversion, Utf8FromUtf16Unicode) {
-  EXPECT_EQ(Utf8FromUtf16(L"\x2603"), "\xe2\x98\x83");
-}
-
-}  // namespace testing
-}  // namespace flutter
diff --git a/shell/platform/windows/system_utils_win32.cc b/shell/platform/windows/system_utils_win32.cc
index 23147296c1604..7df7794477817 100644
--- a/shell/platform/windows/system_utils_win32.cc
+++ b/shell/platform/windows/system_utils_win32.cc
@@ -8,7 +8,7 @@
 
 #include <sstream>
 
-#include "flutter/shell/platform/windows/string_conversion.h"
+#include "flutter/fml/platform/win/wstring_conversion.h"
 
 namespace flutter {
 
@@ -65,7 +65,7 @@ LanguageInfo ParseLanguageName(std::wstring language_name) {
 
   // Split by '-', discarding any suplemental language info (-x-foo).
   std::vector<std::string> components;
-  std::istringstream stream(Utf8FromUtf16(language_name));
+  std::istringstream stream(fml::WideStringToUtf8(language_name));
   std::string component;
   while (getline(stream, component, '-')) {
     if (component == "x") {
diff --git a/shell/platform/windows/system_utils_winuwp.cc b/shell/platform/windows/system_utils_winuwp.cc
index cdee09e30f506..698fb1e70abe0 100644
--- a/shell/platform/windows/system_utils_winuwp.cc
+++ b/shell/platform/windows/system_utils_winuwp.cc
@@ -13,7 +13,7 @@
 #include "third_party/cppwinrt/generated/winrt/Windows.UI.ViewManagement.h"
 #include "third_party/cppwinrt/generated/winrt/Windows.UI.h"
 
-#include "flutter/shell/platform/windows/string_conversion.h"
+#include "flutter/fml/platform/win/wstring_conversion.h"
 
 namespace flutter {
 
@@ -41,7 +41,7 @@ LanguageInfo ParseLanguageName(std::wstring language_name) {
 
   // Split by '-', discarding any suplemental language info (-x-foo).
   std::vector<std::string> components;
-  std::istringstream stream(Utf8FromUtf16(language_name));
+  std::istringstream stream(fml::WideStringToUtf8(language_name));
   std::string component;
   while (getline(stream, component, '-')) {
     if (component == "x") {
diff --git a/shell/platform/windows/uwptool_commands.cc b/shell/platform/windows/uwptool_commands.cc
index b524a398f37e1..1a8f5605262ca 100644
--- a/shell/platform/windows/uwptool_commands.cc
+++ b/shell/platform/windows/uwptool_commands.cc
@@ -3,7 +3,7 @@
 #include <iostream>
 #include <sstream>
 
-#include "flutter/shell/platform/windows/string_conversion.h"
+#include "flutter/fml/platform/win/wstring_conversion.h"
 #include "flutter/shell/platform/windows/uwptool_utils.h"
 
 namespace flutter {
@@ -25,10 +25,10 @@ bool InstallCommand::ValidateArgs(const std::vector<std::string>& args) const {
 }
 
 int InstallCommand::Run(const std::vector<std::string>& args) const {
-  std::wstring package_uri = flutter::Utf16FromUtf8(args[0]);
+  std::wstring package_uri = fml::Utf8ToWideString(args[0]);
   std::vector<std::wstring> dependency_uris;
   for (int i = 1; i < args.size(); ++i) {
-    dependency_uris.push_back(flutter::Utf16FromUtf8(args[i]));
+    dependency_uris.push_back(fml::Utf8ToWideString(args[i]));
   }
   flutter::ApplicationStore app_store;
   if (app_store.Install(package_uri, dependency_uris)) {
@@ -45,7 +45,7 @@ bool UninstallCommand::ValidateArgs(
 
 int UninstallCommand::Run(const std::vector<std::string>& args) const {
   flutter::ApplicationStore app_store;
-  std::wstring package_family = flutter::Utf16FromUtf8(args[0]);
+  std::wstring package_family = fml::Utf8ToWideString(args[0]);
   return app_store.Uninstall(package_family) ? 0 : 1;
 }
 
@@ -66,8 +66,8 @@ int LaunchCommand::Run(const std::vector<std::string>& args) const {
     }
   }
   flutter::ApplicationStore app_store;
-  int process_id = app_store.Launch(flutter::Utf16FromUtf8(package_family),
-                                    flutter::Utf16FromUtf8(app_args.str()));
+  int process_id = app_store.Launch(fml::Utf8ToWideString(package_family),
+                                    fml::Utf8ToWideString(app_args.str()));
   if (process_id == -1) {
     std::cerr << "error: Failed to launch app with package family "
               << package_family << " arguments [" << app_args.str() << "]"