diff --git a/CMakeLists.txt b/CMakeLists.txt
index 95ba5236..ec9f5da2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -191,11 +191,11 @@ set(SPDLOG_HEADERS
     "include/spdlog/details/periodic_worker.h"
     "include/spdlog/details/registry.h"
     "include/spdlog/details/synchronous_factory.h"
-    "include/spdlog/details/tcp_client-windows.h"
-    "include/spdlog/details/tcp_client.h"
+
+    "include/spdlog/details/tcp_client_unix.h"
     "include/spdlog/details/thread_pool.h"
-    "include/spdlog/details/udp_client-windows.h"
-    "include/spdlog/details/udp_client.h"
+    "include/spdlog/details/udp_client_windows.h"
+    "include/spdlog/details/udp_client_unix.h"
     "include/spdlog/details/windows_include.h"
     "include/spdlog/fmt/bin_to_hex.h"
     "include/spdlog/fmt/fmt.h"
@@ -236,7 +236,6 @@ set(SPDLOG_SRCS
     "src/details/file_helper.cpp"
     "src/details/log_msg.cpp"
     "src/details/log_msg_buffer.cpp"
-    "src/details/os.cpp"
     "src/details/periodic_worker.cpp"
     "src/details/registry.cpp"
     "src/details/thread_pool.cpp"    
@@ -249,6 +248,15 @@ set(SPDLOG_SRCS
     "src/sinks/stdout_sinks.cpp"
     "src/sinks/wincolor_sink.cpp")
 
+if(WIN32)
+    list(APPEND SPDLOG_SRCS "src/details/os_windows.cpp")
+    list(APPEND SPDLOG_HEADERS "include/spdlog/details/tcp_client_windows.h")
+    list(APPEND SPDLOG_HEADERS "include/spdlog/details/udp_client_windows.h")
+else()
+    list(APPEND SPDLOG_SRCS "src/details/os_unix.cpp")
+    list(APPEND SPDLOG_HEADERS "include/spdlog/details/tcp_client_unix.h")
+    list(APPEND SPDLOG_HEADERS "include/spdlog/details/udp_client_unix.h")
+endif()
 # Generate spdlog_config.h based on the current configuration
 set(OUT_CONFIG_FILE "${CMAKE_CURRENT_SOURCE_DIR}/include/spdlog/spdlog_config.h")
 message(STATUS "Generating ${OUT_CONFIG_FILE}")
@@ -256,7 +264,8 @@ configure_file("${CMAKE_CURRENT_SOURCE_DIR}/cmake/spdlog_config.h.in" ${OUT_CONF
 list(APPEND SPDLOG_HEADERS ${OUT_CONFIG_FILE})
 if(BUILD_SHARED_LIBS)
     if(WIN32)
-        set(VERSION_RC ${CMAKE_CURRENT_BINARY_DIR}/version.rc )
+        set(VERSION_RC ${CMAKE_CURRENT_BINARY_DIR}/version.rc
+                src/details/os_unix.cpp)
         configure_file(${CMAKE_CURRENT_SOURCE_DIR}/cmake/version.rc.in ${CMAKE_CURRENT_BINARY_DIR}/version.rc @ONLY)        
     endif()
     add_library(spdlog SHARED ${SPDLOG_SRCS} ${SPDLOG_HEADERS} ${VERSION_RC})
diff --git a/include/spdlog/details/tcp_client.h b/include/spdlog/details/tcp_client_unix.h
similarity index 97%
rename from include/spdlog/details/tcp_client.h
rename to include/spdlog/details/tcp_client_unix.h
index f92a3684..9364eda5 100644
--- a/include/spdlog/details/tcp_client.h
+++ b/include/spdlog/details/tcp_client_unix.h
@@ -4,7 +4,7 @@
 #pragma once
 
 #ifdef _WIN32
-    #error include tcp_client-windows.h instead
+    #error include tcp_client_windows.h instead
 #endif
 
 // tcp client helper
@@ -23,7 +23,7 @@
 
 namespace spdlog {
 namespace details {
-class tcp_client {
+class tcp_client_unix {
     int socket_ = -1;
 
 public:
@@ -38,7 +38,7 @@ public:
 
     int fd() const { return socket_; }
 
-    ~tcp_client() { close(); }
+    ~tcp_client_unix() { close(); }
 
     // try to connect or throw on failure
     void connect(const std::string &host, int port) {
diff --git a/include/spdlog/details/tcp_client-windows.h b/include/spdlog/details/tcp_client_windows.h
similarity index 97%
rename from include/spdlog/details/tcp_client-windows.h
rename to include/spdlog/details/tcp_client_windows.h
index 49710c92..c626e473 100644
--- a/include/spdlog/details/tcp_client-windows.h
+++ b/include/spdlog/details/tcp_client_windows.h
@@ -22,7 +22,7 @@
 
 namespace spdlog {
 namespace details {
-class tcp_client {
+class tcp_client_unix {
     SOCKET socket_ = INVALID_SOCKET;
 
     static void init_winsock_() {
@@ -42,9 +42,9 @@ class tcp_client {
     }
 
 public:
-    tcp_client() { init_winsock_(); }
+    tcp_client_unix() { init_winsock_(); }
 
-    ~tcp_client() {
+    ~tcp_client_unix() {
         close();
         ::WSACleanup();
     }
diff --git a/include/spdlog/details/udp_client.h b/include/spdlog/details/udp_client_unix.h
similarity index 92%
rename from include/spdlog/details/udp_client.h
rename to include/spdlog/details/udp_client_unix.h
index e0cc4432..1b46da4a 100644
--- a/include/spdlog/details/udp_client.h
+++ b/include/spdlog/details/udp_client_unix.h
@@ -10,7 +10,7 @@
 #include "./os.h"
 
 #ifdef _WIN32
-    #error "include udp_client-windows.h instead"
+    #error "include udp_client_windows.h instead"
 #endif
 
 #include <arpa/inet.h>
@@ -26,7 +26,7 @@
 namespace spdlog {
 namespace details {
 
-class udp_client {
+class udp_client_unix {
     static constexpr int TX_BUFFER_SIZE = 1024 * 10;
     int socket_ = -1;
     struct sockaddr_in sockAddr_;
@@ -39,7 +39,7 @@ class udp_client {
     }
 
 public:
-    udp_client(const std::string &host, uint16_t port) {
+    udp_client_unix(const std::string &host, uint16_t port) {
         socket_ = ::socket(PF_INET, SOCK_DGRAM, 0);
         if (socket_ < 0) {
             throw_spdlog_ex("error: Create Socket Failed!");
@@ -63,7 +63,7 @@ public:
         ::memset(sockAddr_.sin_zero, 0x00, sizeof(sockAddr_.sin_zero));
     }
 
-    ~udp_client() { cleanup_(); }
+    ~udp_client_unix() { cleanup_(); }
 
     int fd() const { return socket_; }
 
diff --git a/include/spdlog/details/udp_client-windows.h b/include/spdlog/details/udp_client_windows.h
similarity index 95%
rename from include/spdlog/details/udp_client-windows.h
rename to include/spdlog/details/udp_client_windows.h
index 8bae36b0..3b952115 100644
--- a/include/spdlog/details/udp_client-windows.h
+++ b/include/spdlog/details/udp_client_windows.h
@@ -25,7 +25,7 @@
 
 namespace spdlog {
 namespace details {
-class udp_client {
+class udp_client_unix {
     static constexpr int TX_BUFFER_SIZE = 1024 * 10;
     SOCKET socket_ = INVALID_SOCKET;
     sockaddr_in addr_ = {};
@@ -55,7 +55,7 @@ class udp_client {
     }
 
 public:
-    udp_client(const std::string &host, uint16_t port) {
+    udp_client_unix(const std::string &host, uint16_t port) {
         init_winsock_();
 
         addr_.sin_family = PF_INET;
@@ -83,7 +83,7 @@ public:
         }
     }
 
-    ~udp_client() { cleanup_(); }
+    ~udp_client_unix() { cleanup_(); }
 
     SOCKET fd() const { return socket_; }
 
diff --git a/include/spdlog/sinks/tcp_sink.h b/include/spdlog/sinks/tcp_sink.h
index d6c7b587..9e1d3333 100644
--- a/include/spdlog/sinks/tcp_sink.h
+++ b/include/spdlog/sinks/tcp_sink.h
@@ -9,7 +9,7 @@
 #ifdef _WIN32
     #include "../details/tcp_client-windows.h"
 #else
-    #include "../details/tcp_client.h"
+    #include "../details/tcp_client_unix.h"
 #endif
 
 #include <chrono>
@@ -65,7 +65,7 @@ protected:
 
     void flush_() override {}
     tcp_sink_config config_;
-    details::tcp_client client_;
+    details::tcp_client_unix client_;
 };
 
 using tcp_sink_mt = tcp_sink<std::mutex>;
diff --git a/include/spdlog/sinks/udp_sink.h b/include/spdlog/sinks/udp_sink.h
index 1735ecf7..e86bd0b0 100644
--- a/include/spdlog/sinks/udp_sink.h
+++ b/include/spdlog/sinks/udp_sink.h
@@ -9,7 +9,7 @@
 #ifdef _WIN32
     #include "../details/udp_client-windows.h"
 #else
-    #include "../details/udp_client.h"
+    #include "../details/udp_client_unix.h"
 #endif
 
 #include <chrono>
@@ -49,7 +49,7 @@ protected:
     }
 
     void flush_() override {}
-    details::udp_client client_;
+    details::udp_client_unix client_;
 };
 
 using udp_sink_mt = udp_sink<std::mutex>;
diff --git a/src/details/os.cpp b/src/details/os_unix.cpp
similarity index 55%
rename from src/details/os.cpp
rename to src/details/os_unix.cpp
index 790a2217..c4e0390a 100644
--- a/src/details/os.cpp
+++ b/src/details/os_unix.cpp
@@ -1,9 +1,9 @@
 // Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
 // Distributed under the MIT License (http://opensource.org/licenses/MIT)
 
-#include "spdlog/details/os.h"
-
+#include <fcntl.h>
 #include <sys/stat.h>
+#include <unistd.h>
 
 #include <algorithm>
 #include <array>
@@ -16,47 +16,23 @@
 #include <thread>
 
 #include "spdlog/common.h"
+#include "spdlog/details/os.h"
 
-// clang-format off
-#ifdef _WIN32
-    #include "spdlog/details/windows_include.h"
-    #include <fileapi.h>  // for FlushFileBuffers
-    #include <io.h>       // for _get_osfhandle, _isatty, _fileno
-    #include <process.h>  // for _get_pid
+#ifdef __linux__
+    #include <sys/syscall.h>  //Use gettid() syscall under linux to get thread id
 
-    #ifdef __MINGW32__
-        #include <share.h>
-    #endif
+#elif defined(_AIX)
+    #include <pthread.h>  // for pthread_getthrds_np
 
-    #if defined(SPDLOG_WCHAR_FILENAMES)
-        #include <cassert>
-        #include <limits>
-    #endif
+#elif defined(__DragonFly__) || defined(__FreeBSD__)
+    #include <pthread_np.h>  // for pthread_getthreadid_np
 
-    #include <direct.h>  // for _mkdir/_wmkdir
+#elif defined(__NetBSD__)
+    #include <lwp.h>  // for _lwp_self
 
-#else  // unix
-
-    #include <fcntl.h>
-    #include <unistd.h>
-
-    #ifdef __linux__
-        #include <sys/syscall.h>  //Use gettid() syscall under linux to get thread id
-
-    #elif defined(_AIX)
-        #include <pthread.h>  // for pthread_getthrds_np
-
-    #elif defined(__DragonFly__) || defined(__FreeBSD__)
-        #include <pthread_np.h>  // for pthread_getthreadid_np
-
-    #elif defined(__NetBSD__)
-        #include <lwp.h>  // for _lwp_self
-
-    #elif defined(__sun)
-        #include <thread.h>  // for thr_self
-    #endif
-
-#endif  // _WIN32
+#elif defined(__sun)
+    #include <thread.h>  // for thr_self
+#endif
 
 #if defined __APPLE__
     #include <AvailabilityMacros.h>
@@ -84,15 +60,9 @@ spdlog::log_clock::time_point now() noexcept {
 #endif
 }
 std::tm localtime(const std::time_t &time_tt) noexcept {
-#ifdef _WIN32
-    std::tm tm;
-    const auto rv = ::localtime_s(&tm, &time_tt);
-    return rv == 0 ? tm : std::tm{};
-#else
     std::tm tm;
     const auto *rv = ::localtime_r(&time_tt, &tm);
     return rv != nullptr ? tm : std::tm{};
-#endif
 }
 
 std::tm localtime() noexcept {
@@ -101,13 +71,8 @@ std::tm localtime() noexcept {
 }
 
 std::tm gmtime(const std::time_t &time_tt) noexcept {
-#ifdef _WIN32
-    std::tm tm;
-    ::gmtime_s(&tm, &time_tt);
-#else
     std::tm tm;
     ::gmtime_r(&time_tt, &tm);
-#endif
     return tm;
 }
 
@@ -118,23 +83,7 @@ std::tm gmtime() noexcept {
 
 // fopen_s on non windows for writing
 bool fopen_s(FILE **fp, const filename_t &filename, const filename_t &mode) {
-#ifdef _WIN32
-    #ifdef SPDLOG_WCHAR_FILENAMES
-    *fp = ::_wfsopen((filename.c_str()), mode.c_str(), _SH_DENYNO);
-    #else
-    *fp = ::_fsopen((filename.c_str()), mode.c_str(), _SH_DENYNO);
-    #endif
-    #if defined(SPDLOG_PREVENT_CHILD_FD)
-    if (*fp != nullptr) {
-        auto file_handle = reinterpret_cast<HANDLE>(_get_osfhandle(::_fileno(*fp)));
-        if (!::SetHandleInformation(file_handle, HANDLE_FLAG_INHERIT, 0)) {
-            ::fclose(*fp);
-            *fp = nullptr;
-        }
-    }
-    #endif
-#else  // unix
-    #if defined(SPDLOG_PREVENT_CHILD_FD)
+#if defined(SPDLOG_PREVENT_CHILD_FD)
     const int mode_flag = mode == SPDLOG_FILENAME_T("ab") ? O_APPEND : O_TRUNC;
     const int fd = ::open((filename.c_str()), O_CREAT | O_WRONLY | O_CLOEXEC | mode_flag, mode_t(0644));
     if (fd == -1) {
@@ -144,124 +93,58 @@ bool fopen_s(FILE **fp, const filename_t &filename, const filename_t &mode) {
     if (*fp == nullptr) {
         ::close(fd);
     }
-    #else
+#else
     *fp = ::fopen((filename.c_str()), mode.c_str());
-    #endif
 #endif
-
     return *fp == nullptr;
 }
 
-int remove(const filename_t &filename) noexcept {
-#if defined(_WIN32) && defined(SPDLOG_WCHAR_FILENAMES)
-    return ::_wremove(filename.c_str());
-#else
-    return std::remove(filename.c_str());
-#endif
-}
+int remove(const filename_t &filename) noexcept { return std::remove(filename.c_str()); }
 
 int remove_if_exists(const filename_t &filename) noexcept { return path_exists(filename) ? remove(filename) : 0; }
 
 int rename(const filename_t &filename1, const filename_t &filename2) noexcept {
-#if defined(_WIN32) && defined(SPDLOG_WCHAR_FILENAMES)
-    return ::_wrename(filename1.c_str(), filename2.c_str());
-#else
     return std::rename(filename1.c_str(), filename2.c_str());
-#endif
 }
 
 // Return true if path exists (file or directory)
 bool path_exists(const filename_t &filename) noexcept {
-#ifdef _WIN32
-    #ifdef SPDLOG_WCHAR_FILENAMES
-    auto attribs = ::GetFileAttributesW(filename.c_str());
-    #else
-    auto attribs = ::GetFileAttributesA(filename.c_str());
-    #endif
-    return attribs != INVALID_FILE_ATTRIBUTES;
-#else  // common linux/unix all have the stat system call
     struct stat buffer;
     return (::stat(filename.c_str(), &buffer) == 0);
-#endif
 }
 
-#ifdef _MSC_VER
-    // avoid warning about unreachable statement at the end of filesize()
-    #pragma warning(push)
-    #pragma warning(disable : 4702)
-#endif
-
 // Return file size according to open FILE* object
 size_t filesize(FILE *f) {
     if (f == nullptr) {
         throw_spdlog_ex("Failed getting file size. fd is null");
     }
-#if defined(_WIN32) && !defined(__CYGWIN__)
-    int fd = ::_fileno(f);
-    #if defined(_WIN64)  // 64 bits
-    __int64 ret = ::_filelengthi64(fd);
-    if (ret >= 0) {
-        return static_cast<size_t>(ret);
-    }
 
-    #else  // windows 32 bits
-    long ret = ::_filelength(fd);
-    if (ret >= 0) {
-        return static_cast<size_t>(ret);
-    }
-    #endif
-
-#else  // unix
     // OpenBSD and AIX doesn't compile with :: before the fileno(..)
-    #if defined(__OpenBSD__) || defined(_AIX)
+#if defined(__OpenBSD__) || defined(_AIX)
     int fd = fileno(f);
-    #else
+#else
     int fd = ::fileno(f);
-    #endif
+#endif
     // 64 bits(but not in osx, linux/musl or cygwin, where fstat64 is deprecated)
-    #if ((defined(__linux__) && defined(__GLIBC__)) || defined(__sun) || defined(_AIX)) && (defined(__LP64__) || defined(_LP64))
+#if ((defined(__linux__) && defined(__GLIBC__)) || defined(__sun) || defined(_AIX)) && (defined(__LP64__) || defined(_LP64))
     struct stat64 st;
     if (::fstat64(fd, &st) == 0) {
         return static_cast<size_t>(st.st_size);
     }
-    #else  // other unix or linux 32 bits or cygwin
+#else  // other unix or linux 32 bits or cygwin
     struct stat st;
     if (::fstat(fd, &st) == 0) {
         return static_cast<size_t>(st.st_size);
     }
-    #endif
 #endif
     throw_spdlog_ex("Failed getting file size from fd", errno);
     return 0;  // will not be reached.
 }
 
-#ifdef _MSC_VER
-    #pragma warning(pop)
-#endif
-
 // Return utc offset in minutes or throw spdlog_ex on failure
 int utc_minutes_offset(const std::tm &tm) {
-#ifdef _WIN32
-    #if _WIN32_WINNT < _WIN32_WINNT_WS08
-    TIME_ZONE_INFORMATION tzinfo;
-    auto rv = ::GetTimeZoneInformation(&tzinfo);
-    #else
-    DYNAMIC_TIME_ZONE_INFORMATION tzinfo;
-    auto rv = ::GetDynamicTimeZoneInformation(&tzinfo);
-    #endif
-    if (rv == TIME_ZONE_ID_INVALID) throw_spdlog_ex("Failed getting timezone info. ", errno);
-
-    int offset = -tzinfo.Bias;
-    if (tm.tm_isdst) {
-        offset -= tzinfo.DaylightBias;
-    } else {
-        offset -= tzinfo.StandardBias;
-    }
-    return offset;
-#else
-
-    #if defined(sun) || defined(__sun) || defined(_AIX) || (defined(__NEWLIB__) && !defined(__TM_GMTOFF)) || \
-        (!defined(_BSD_SOURCE) && !defined(_GNU_SOURCE))
+#if defined(sun) || defined(__sun) || defined(_AIX) || (defined(__NEWLIB__) && !defined(__TM_GMTOFF)) || \
+    (!defined(_BSD_SOURCE) && !defined(_GNU_SOURCE))
     // 'tm_gmtoff' field is BSD extension and it's missing on SunOS/Solaris
     struct helper {
         static long int calculate_gmt_offset(const std::tm &localtm = details::os::localtime(),
@@ -290,21 +173,17 @@ int utc_minutes_offset(const std::tm &tm) {
     };
 
     auto offset_seconds = helper::calculate_gmt_offset(tm);
-    #else
+#else
     auto offset_seconds = tm.tm_gmtoff;
-    #endif
-
-    return static_cast<int>(offset_seconds / 60);
 #endif
+    return static_cast<int>(offset_seconds / 60);
 }
 
 // Return current thread id as size_t
 // It exists because the std::this_thread::get_id() is much slower(especially
 // under VS 2013)
 size_t _thread_id() noexcept {
-#ifdef _WIN32
-    return static_cast<size_t>(::GetCurrentThreadId());
-#elif defined(__linux__)
+#if defined(__linux__)
     #if defined(__ANDROID__) && defined(__ANDROID_API__) && (__ANDROID_API__ < 21)
         #define SYS_gettid __NR_gettid
     #endif
@@ -358,42 +237,17 @@ size_t thread_id() noexcept {
     return tid;
 }
 
-// This is avoid msvc issue in sleep_for that happens if the clock changes.
-// See https://github.com/gabime/spdlog/issues/609
 void sleep_for_millis(unsigned int milliseconds) noexcept {
-#if defined(_WIN32)
-    ::Sleep(milliseconds);
-#else
     std::this_thread::sleep_for(std::chrono::milliseconds(milliseconds));
-#endif
 }
 
-// wchar support for windows file names (SPDLOG_WCHAR_FILENAMES must be defined)
-#if defined(_WIN32) && defined(SPDLOG_WCHAR_FILENAMES)
-std::string filename_to_str(const filename_t &filename) {
-    memory_buf_t buf;
-    wstr_to_utf8buf(filename, buf);
-    return SPDLOG_BUF_TO_STRING(buf);
-}
-#else
 std::string filename_to_str(const filename_t &filename) { return filename; }
-#endif
 
-int pid() noexcept {
-#ifdef _WIN32
-    return static_cast<int>(::GetCurrentProcessId());
-#else
-    return static_cast<int>(::getpid());
-#endif
-}
+int pid() noexcept { return static_cast<int>(::getpid()); }
 
 // Determine if the terminal supports colors
 // Based on: https://github.com/agauniyal/rang/
 bool is_color_terminal() noexcept {
-#ifdef _WIN32
-    return true;
-#else
-
     static const bool result = []() {
         const char *env_colorterm_p = std::getenv("COLORTERM");
         if (env_colorterm_p != nullptr) {
@@ -414,88 +268,14 @@ bool is_color_terminal() noexcept {
     }();
 
     return result;
-#endif
 }
 
 // Determine if the terminal attached
 // Source: https://github.com/agauniyal/rang/
-bool in_terminal(FILE *file) noexcept {
-#ifdef _WIN32
-    return ::_isatty(_fileno(file)) != 0;
-#else
-    return ::isatty(fileno(file)) != 0;
-#endif
-}
-
-#if defined(SPDLOG_WCHAR_FILENAMES) && defined(_WIN32)
-void wstr_to_utf8buf(wstring_view_t wstr, memory_buf_t &target) {
-    if (wstr.size() > static_cast<size_t>((std::numeric_limits<int>::max)()) / 2 - 1) {
-        throw_spdlog_ex("UTF-16 string is too big to be converted to UTF-8");
-    }
-
-    int wstr_size = static_cast<int>(wstr.size());
-    if (wstr_size == 0) {
-        target.resize(0);
-        return;
-    }
-
-    int result_size = static_cast<int>(target.capacity());
-    if ((wstr_size + 1) * 2 > result_size) {
-        result_size = ::WideCharToMultiByte(CP_UTF8, 0, wstr.data(), wstr_size, NULL, 0, NULL, NULL);
-    }
-
-    if (result_size > 0) {
-        target.resize(result_size);
-        result_size = ::WideCharToMultiByte(CP_UTF8, 0, wstr.data(), wstr_size, target.data(), result_size, NULL, NULL);
-
-        if (result_size > 0) {
-            target.resize(result_size);
-            return;
-        }
-    }
-
-    throw_spdlog_ex(fmt_lib::format("WideCharToMultiByte failed. Last error: {}", ::GetLastError()));
-}
-
-void utf8_to_wstrbuf(string_view_t str, wmemory_buf_t &target) {
-    if (str.size() > static_cast<size_t>((std::numeric_limits<int>::max)()) - 1) {
-        throw_spdlog_ex("UTF-8 string is too big to be converted to UTF-16");
-    }
-
-    int str_size = static_cast<int>(str.size());
-    if (str_size == 0) {
-        target.resize(0);
-        return;
-    }
-
-    // find the size to allocate for the result buffer
-    int result_size = ::MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, str.data(), str_size, NULL, 0);
-
-    if (result_size > 0) {
-        target.resize(result_size);
-        result_size = ::MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, str.data(), str_size, target.data(), result_size);
-        if (result_size > 0) {
-            assert(result_size == target.size());
-            return;
-        }
-    }
-
-    throw_spdlog_ex(fmt_lib::format("MultiByteToWideChar failed. Last error: {}", ::GetLastError()));
-}
-#endif  // defined(SPDLOG_WCHAR_FILENAMES) && defined(_WIN32)
+bool in_terminal(FILE *file) noexcept { return ::isatty(fileno(file)) != 0; }
 
 // return true on success
-static bool mkdir_(const filename_t &path) {
-#ifdef _WIN32
-    #ifdef SPDLOG_WCHAR_FILENAMES
-    return ::_wmkdir(path.c_str()) == 0;
-    #else
-    return ::_mkdir(path.c_str()) == 0;
-    #endif
-#else
-    return ::mkdir(path.c_str(), mode_t(0755)) == 0;
-#endif
-}
+static bool mkdir_(const filename_t &path) { return ::mkdir(path.c_str(), mode_t(0755)) == 0; }
 
 // create the given directory - and all directories leading to it
 // return true on success or if the directory already exists
@@ -538,30 +318,13 @@ filename_t dir_name(const filename_t &path) {
 }
 
 std::string getenv(const char *field) {
-#if defined(_MSC_VER)
-    #if defined(__cplusplus_winrt)
-    return std::string{};  // not supported under uwp
-    #else
-    size_t len = 0;
-    char buf[128];
-    bool ok = ::getenv_s(&len, buf, sizeof(buf), field) == 0;
-    return ok ? buf : std::string{};
-    #endif
-#else  // revert to getenv
     char *buf = ::getenv(field);
     return buf != nullptr ? buf : std::string{};
-#endif
 }
 
 // Do fsync by FILE handlerpointer
 // Return true on success
-bool fsync(FILE *fp) {
-#ifdef _WIN32
-    return FlushFileBuffers(reinterpret_cast<HANDLE>(_get_osfhandle(_fileno(fp)))) != 0;
-#else
-    return ::fsync(fileno(fp)) == 0;
-#endif
-}
+bool fsync(FILE *fp) { return ::fsync(fileno(fp)) == 0; }
 
 }  // namespace os
 }  // namespace details
diff --git a/src/details/os_windows.cpp b/src/details/os_windows.cpp
new file mode 100644
index 00000000..0f87a678
--- /dev/null
+++ b/src/details/os_windows.cpp
@@ -0,0 +1,328 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#ifndef _WIN32
+    #error "_WIN32 only source file"
+#endif
+
+#include <fileapi.h>  // for FlushFileBuffers
+#include <io.h>       // for _get_osfhandle, _isatty, _fileno
+#include <process.h>  // for _get_pid
+#include <sys/stat.h>
+
+#include <algorithm>
+#include <array>
+#include <chrono>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <ctime>
+#include <string>
+#include <thread>
+
+#include "spdlog/common.h"
+#include "spdlog/details/os.h"
+#include "spdlog/details/windows_include.h"
+
+#ifdef __MINGW32__
+    #include <share.h>
+#endif
+
+#if defined(SPDLOG_WCHAR_FILENAMES)
+    #include <cassert>
+    #include <limits>
+#endif
+
+#include <direct.h>  // for _mkdir/_wmkdir
+
+// clang-format on
+namespace spdlog {
+namespace details {
+namespace os {
+spdlog::log_clock::time_point now() noexcept { return log_clock::now(); }
+
+std::tm localtime(const std::time_t &time_tt) noexcept {
+    std::tm tm;
+    const auto rv = ::localtime_s(&tm, &time_tt);
+    return rv == 0 ? tm : std::tm{};
+}
+
+std::tm localtime() noexcept {
+    std::time_t now_t = ::time(nullptr);
+    return localtime(now_t);
+}
+
+std::tm gmtime(const std::time_t &time_tt) noexcept {
+    std::tm tm;
+    ::gmtime_s(&tm, &time_tt);
+    return tm;
+}
+
+std::tm gmtime() noexcept {
+    std::time_t now_t = ::time(nullptr);
+    return gmtime(now_t);
+}
+
+bool fopen_s(FILE **fp, const filename_t &filename, const filename_t &mode) {
+#ifdef SPDLOG_WCHAR_FILENAMES
+    *fp = ::_wfsopen((filename.c_str()), mode.c_str(), _SH_DENYNO);
+#else
+    *fp = ::_fsopen((filename.c_str()), mode.c_str(), _SH_DENYNO);
+#endif
+#if defined(SPDLOG_PREVENT_CHILD_FD)
+    if (*fp != nullptr) {
+        auto file_handle = reinterpret_cast<HANDLE>(_get_osfhandle(::_fileno(*fp)));
+        if (!::SetHandleInformation(file_handle, HANDLE_FLAG_INHERIT, 0)) {
+            ::fclose(*fp);
+            *fp = nullptr;
+        }
+    }
+#endif
+    return *fp == nullptr;
+}
+
+int remove(const filename_t &filename) noexcept {
+#if defined(SPDLOG_WCHAR_FILENAMES)
+    return ::_wremove(filename.c_str());
+#else
+    return std::remove(filename.c_str());
+#endif
+}
+
+int remove_if_exists(const filename_t &filename) noexcept { return path_exists(filename) ? remove(filename) : 0; }
+
+int rename(const filename_t &filename1, const filename_t &filename2) noexcept {
+#if defined(SPDLOG_WCHAR_FILENAMES)
+    return ::_wrename(filename1.c_str(), filename2.c_str());
+#else
+    return std::rename(filename1.c_str(), filename2.c_str());
+#endif
+}
+
+// Return true if path exists (file or directory)
+bool path_exists(const filename_t &filename) noexcept {
+#ifdef SPDLOG_WCHAR_FILENAMES
+    auto attribs = ::GetFileAttributesW(filename.c_str());
+#else
+    auto attribs = ::GetFileAttributesA(filename.c_str());
+#endif
+    return attribs != INVALID_FILE_ATTRIBUTES;
+}
+
+#ifdef _MSC_VER
+// avoid warning about unreachable statement at the end of filesize()
+    #pragma warning(push)
+    #pragma warning(disable : 4702)
+#endif
+
+// Return file size according to open FILE* object
+size_t filesize(FILE *f) {
+    if (f == nullptr) {
+        throw_spdlog_ex("Failed getting file size. fd is null");
+    }
+    int fd = ::_fileno(f);
+#if defined(_WIN64)  // 64 bits
+    __int64 ret = ::_filelengthi64(fd);
+    if (ret >= 0) {
+        return static_cast<size_t>(ret);
+    }
+
+#else  // windows 32 bits
+    long ret = ::_filelength(fd);
+    if (ret >= 0) {
+        return static_cast<size_t>(ret);
+    }
+#endif
+    throw_spdlog_ex("Failed getting file size from fd", errno);
+    return 0;  // will not be reached.
+}
+
+#ifdef _MSC_VER
+    #pragma warning(pop)
+#endif
+
+// Return utc offset in minutes or throw spdlog_ex on failure
+int utc_minutes_offset(const std::tm &tm) {
+#if _WIN32_WINNT < _WIN32_WINNT_WS08
+    TIME_ZONE_INFORMATION tzinfo;
+    auto rv = ::GetTimeZoneInformation(&tzinfo);
+#else
+    DYNAMIC_TIME_ZONE_INFORMATION tzinfo;
+    auto rv = ::GetDynamicTimeZoneInformation(&tzinfo);
+#endif
+    if (rv == TIME_ZONE_ID_INVALID) throw_spdlog_ex("Failed getting timezone info. ", errno);
+
+    int offset = -tzinfo.Bias;
+    if (tm.tm_isdst) {
+        offset -= tzinfo.DaylightBias;
+    } else {
+        offset -= tzinfo.StandardBias;
+    }
+    return offset;
+}
+
+// Return current thread id as size_t
+// It exists because the std::this_thread::get_id() is much slower(especially
+// under VS 2013)
+size_t _thread_id() noexcept { return static_cast<size_t>(::GetCurrentThreadId()); }
+
+// Return current thread id as size_t (from thread local storage)
+size_t thread_id() noexcept {
+    // cache thread id in tls
+    static thread_local const size_t tid = _thread_id();
+    return tid;
+}
+
+// This is avoid msvc issue in sleep_for that happens if the clock changes.
+// See https://github.com/gabime/spdlog/issues/609
+void sleep_for_millis(unsigned int milliseconds) noexcept { ::Sleep(milliseconds); }
+
+// wchar support for windows file names (SPDLOG_WCHAR_FILENAMES must be defined)
+#if defined(SPDLOG_WCHAR_FILENAMES)
+std::string filename_to_str(const filename_t &filename) {
+    memory_buf_t buf;
+    wstr_to_utf8buf(filename, buf);
+    return SPDLOG_BUF_TO_STRING(buf);
+}
+#else
+std::string filename_to_str(const filename_t &filename) { return filename; }
+#endif
+
+int pid() noexcept { return static_cast<int>(::GetCurrentProcessId()); }
+
+
+bool is_color_terminal() noexcept { return true; }
+
+// Determine if the terminal attached
+bool in_terminal(FILE *file) noexcept { return ::_isatty(_fileno(file)) != 0; }
+
+#if defined(SPDLOG_WCHAR_FILENAMES)
+void wstr_to_utf8buf(wstring_view_t wstr, memory_buf_t &target) {
+    if (wstr.size() > static_cast<size_t>((std::numeric_limits<int>::max)()) / 2 - 1) {
+        throw_spdlog_ex("UTF-16 string is too big to be converted to UTF-8");
+    }
+
+    int wstr_size = static_cast<int>(wstr.size());
+    if (wstr_size == 0) {
+        target.resize(0);
+        return;
+    }
+
+    int result_size = static_cast<int>(target.capacity());
+    if ((wstr_size + 1) * 2 > result_size) {
+        result_size = ::WideCharToMultiByte(CP_UTF8, 0, wstr.data(), wstr_size, NULL, 0, NULL, NULL);
+    }
+
+    if (result_size > 0) {
+        target.resize(result_size);
+        result_size = ::WideCharToMultiByte(CP_UTF8, 0, wstr.data(), wstr_size, target.data(), result_size, NULL, NULL);
+
+        if (result_size > 0) {
+            target.resize(result_size);
+            return;
+        }
+    }
+
+    throw_spdlog_ex(fmt_lib::format("WideCharToMultiByte failed. Last error: {}", ::GetLastError()));
+}
+
+void utf8_to_wstrbuf(string_view_t str, wmemory_buf_t &target) {
+    if (str.size() > static_cast<size_t>((std::numeric_limits<int>::max)()) - 1) {
+        throw_spdlog_ex("UTF-8 string is too big to be converted to UTF-16");
+    }
+
+    int str_size = static_cast<int>(str.size());
+    if (str_size == 0) {
+        target.resize(0);
+        return;
+    }
+
+    // find the size to allocate for the result buffer
+    int result_size = ::MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, str.data(), str_size, NULL, 0);
+
+    if (result_size > 0) {
+        target.resize(result_size);
+        result_size = ::MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, str.data(), str_size, target.data(), result_size);
+        if (result_size > 0) {
+            assert(result_size == target.size());
+            return;
+        }
+    }
+
+    throw_spdlog_ex(fmt_lib::format("MultiByteToWideChar failed. Last error: {}", ::GetLastError()));
+}
+#endif  // defined(SPDLOG_WCHAR_FILENAMES)
+
+// return true on success
+static bool mkdir_(const filename_t &path) {
+#
+#ifdef SPDLOG_WCHAR_FILENAMES
+    return ::_wmkdir(path.c_str()) == 0;
+#else
+    return ::_mkdir(path.c_str()) == 0;
+#endif
+}
+
+// create the given directory - and all directories leading to it
+// return true on success or if the directory already exists
+bool create_dir(const filename_t &path) {
+    if (path_exists(path)) {
+        return true;
+    }
+
+    if (path.empty()) {
+        return false;
+    }
+
+    size_t search_offset = 0;
+    do {
+        auto token_pos = path.find_first_of(folder_seps_filename, search_offset);
+        // treat the entire path as a folder if no folder separator not found
+        if (token_pos == filename_t::npos) {
+            token_pos = path.size();
+        }
+
+        auto subdir = path.substr(0, token_pos);
+
+        if (!subdir.empty() && !path_exists(subdir) && !mkdir_(subdir)) {
+            return false;  // return error if failed creating dir
+        }
+        search_offset = token_pos + 1;
+    } while (search_offset < path.size());
+
+    return true;
+}
+
+// Return directory name from given path or empty string
+// "abc/file" => "abc"
+// "abc/" => "abc"
+// "abc" => ""
+// "abc///" => "abc//"
+filename_t dir_name(const filename_t &path) {
+    auto pos = path.find_last_of(folder_seps_filename);
+    return pos != filename_t::npos ? path.substr(0, pos) : filename_t{};
+}
+
+std::string getenv(const char *field) {
+#if defined(_MSC_VER)
+    #if defined(__cplusplus_winrt)
+    return std::string{};  // not supported under uwp
+    #else
+    size_t len = 0;
+    char buf[128];
+    bool ok = ::getenv_s(&len, buf, sizeof(buf), field) == 0;
+    return ok ? buf : std::string{};
+    #endif
+#else  // revert to getenv
+    char *buf = ::getenv(field);
+    return buf != nullptr ? buf : std::string{};
+#endif
+}
+
+// Do fsync by FILE handlerpointer
+// Return true on success
+bool fsync(FILE *fp) { return FlushFileBuffers(reinterpret_cast<HANDLE>(_get_osfhandle(_fileno(fp)))) != 0; }
+
+}  // namespace os
+}  // namespace details
+}  // namespace spdlog