diff --git a/src/audio/playback/decklink.cpp b/src/audio/playback/decklink.cpp
index b84bb4043..d9cbd397a 100644
--- a/src/audio/playback/decklink.cpp
+++ b/src/audio/playback/decklink.cpp
@@ -57,7 +57,7 @@
 #include "video_codec.h"
 #include "video_capture.h"
 
-#ifndef WIN32
+#ifndef _WIN32
 #define STDMETHODCALLTYPE
 #endif
 
diff --git a/src/blackmagic_common.cpp b/src/blackmagic_common.cpp
index 9b8019656..a2e558945 100644
--- a/src/blackmagic_common.cpp
+++ b/src/blackmagic_common.cpp
@@ -107,7 +107,7 @@ char *get_cstr_from_bmd_api_str(BMD_STR bmd_string)
        size_t len = CFStringGetMaximumSizeForEncoding(CFStringGetLength(bmd_string), kCFStringEncodingUTF8) + 1;
        cstr = (char *) malloc(len);
        CFStringGetCString(bmd_string, (char *) cstr, len, kCFStringEncodingUTF8);
-#elif defined WIN32
+#elif defined _WIN32
        size_t len = SysStringLen(bmd_string) * 4 + 1;
        cstr = (char *) malloc(len);
        wcstombs((char *) cstr, bmd_string, len);
@@ -141,7 +141,7 @@ void release_bmd_api_str(BMD_STR string)
         }
 #ifdef HAVE_MACOSX
         CFRelease(string);
-#elif defined WIN32
+#elif defined _WIN32
         SysFreeString(string);
 #else
         free(const_cast<char *>(string));
@@ -165,7 +165,7 @@ std::string get_str_from_bmd_api_str(BMD_STR string)
 IDeckLinkIterator *create_decklink_iterator(bool *com_initialized, bool verbose, bool coinit)
 {
         IDeckLinkIterator *deckLinkIterator = nullptr;
-#ifdef WIN32
+#ifdef _WIN32
         if (coinit) {
                 com_initialize(com_initialized, "[BMD] ");
         }
@@ -206,7 +206,7 @@ bool blackmagic_api_version_check()
         if (!com_initialize(&com_initialized, "[BMD] ")) {
                 goto cleanup;
         }
-#ifdef WIN32
+#ifdef _WIN32
         result = CoCreateInstance(CLSID_CDeckLinkAPIInformation, NULL, CLSCTX_ALL,
                 IID_IDeckLinkAPIInformation, (void **) &APIInformation);
         if(FAILED(result)) {
@@ -249,7 +249,7 @@ void print_decklink_version()
         IDeckLinkAPIInformation *APIInformation = NULL;
         HRESULT result;
 
-#ifdef WIN32
+#ifdef _WIN32
         bool com_initialized = false;
         if (!com_initialize(&com_initialized, "[BMD] ")) {
                 goto cleanup;
@@ -282,7 +282,7 @@ cleanup:
         if (APIInformation) {
                 APIInformation->Release();
         }
-#ifdef WIN32
+#ifdef _WIN32
         com_uninitialize(&com_initialized);
 #endif
 }
diff --git a/src/blackmagic_common.hpp b/src/blackmagic_common.hpp
index 740793451..21d881f87 100644
--- a/src/blackmagic_common.hpp
+++ b/src/blackmagic_common.hpp
@@ -68,7 +68,7 @@ static std::vector<std::pair<codec_t, BMDPixelFormat>> uv_to_bmd_codec_map = {
                   { UYVY, bmdFormat8BitYUV },
 };
 
-#ifdef WIN32
+#ifdef _WIN32
 #define BMD_BOOL BOOL
 #define BMD_TRUE TRUE
 #define BMD_FALSE FALSE
diff --git a/src/bluefish444_common.h b/src/bluefish444_common.h
index 2f872c0e7..1ae333bf3 100644
--- a/src/bluefish444_common.h
+++ b/src/bluefish444_common.h
@@ -46,7 +46,7 @@
 
 #include "debug.h"
 
-#ifdef WIN32
+#ifdef _WIN32
 #include <objbase.h>
 #include <BlueVelvetC_UltraGrid.h>
 #else
diff --git a/src/compat/alarm.h b/src/compat/alarm.h
index 49601a948..d65146ea9 100644
--- a/src/compat/alarm.h
+++ b/src/compat/alarm.h
@@ -38,7 +38,7 @@
  * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifdef WIN32
+#ifdef _WIN32
 
 #ifndef COMPAT_ALARM_H
 #define COMPAT_ALARM_H
@@ -49,4 +49,4 @@ EXTERN_C void alarm(unsigned int sec);
 
 #endif // defined COMPAT_ALARM_H
 
-#endif /* WIN32 */
+#endif /* _WIN32 */
diff --git a/src/compat/platform_pipe.cpp b/src/compat/platform_pipe.cpp
index 75b789285..ba81637e0 100644
--- a/src/compat/platform_pipe.cpp
+++ b/src/compat/platform_pipe.cpp
@@ -154,7 +154,7 @@ static int system_pipe(fd_t p[2])
 
 int platform_pipe_init(fd_t p[2])
 {
-#ifdef WIN32
+#ifdef _WIN32
         // This needs to be called twice, indeed, since WSACleanup will be run
         // on both ends. This call is also required because not all pipes are
         // destroyed before common_cleanup which calls WSACleanup
@@ -227,7 +227,7 @@ int platform_pipe_init(fd_t p[2])
 void platform_pipe_close(fd_t pipe)
 {
         CLOSESOCKET(pipe);
-#ifdef WIN32
+#ifdef _WIN32
         WSACleanup();
 #endif
 }
diff --git a/src/config_unix.h b/src/config_unix.h
index f76adeba3..5f4186c3c 100644
--- a/src/config_unix.h
+++ b/src/config_unix.h
@@ -208,4 +208,4 @@ CONF_NIX_EXT_C int __xpg_strerror_r(int errcode, char *buffer, size_t length);
 #endif // ! defined __STDC_LIB_EXT1__
 
 #endif /* _CONFIG_UNIX_H */
-#endif /* NDEF WIN32 */
+#endif /* NDEF _WIN32 */
diff --git a/src/control_socket.cpp b/src/control_socket.cpp
index 0336993f6..2c8856801 100644
--- a/src/control_socket.cpp
+++ b/src/control_socket.cpp
@@ -61,11 +61,11 @@
 
 #define MAX_CLIENTS 16
 
-#ifdef WIN32
+#ifdef _WIN32
 typedef const char *sso_val_type;
 #else
 typedef void *sso_val_type;
-#endif                          /* WIN32 */
+#endif // defined _WIN32
 
 using namespace std;
 
diff --git a/src/debug.cpp b/src/debug.cpp
index d33f439af..5897d420b 100644
--- a/src/debug.cpp
+++ b/src/debug.cpp
@@ -70,7 +70,7 @@ static void _dprintf(const char *format, ...)
                 return;
         }
 
-#ifdef WIN32
+#ifdef _WIN32
         char msg[65535];
         va_list ap;
 
@@ -84,7 +84,7 @@ static void _dprintf(const char *format, ...)
         va_start(ap, format);
         vfprintf(stderr, format, ap);
         va_end(ap);
-#endif                          /* WIN32 */
+#endif                          /* _WIN32 */
 }
 
 static void
diff --git a/src/gl_context.c b/src/gl_context.c
index d2186da1e..b5c8df3c6 100644
--- a/src/gl_context.c
+++ b/src/gl_context.c
@@ -41,8 +41,6 @@
 #include "config_win32.h"
 #endif
 
-#if defined HAVE_MACOSX || (defined HAVE_LINUX && defined HAVE_LIBGL) || defined WIN32
-
 #include <stdio.h>
 
 #ifdef HAVE_MACOSX
@@ -50,7 +48,7 @@
 #elif defined HAVE_LINUX
 #include "x11_common.h"
 #include "glx_common.h"
-#else // WIN32
+#else // _WIN32
 #include "win32_gl_common.h"
 #endif
 
@@ -103,7 +101,7 @@ bool init_gl_context(struct gl_context *context, int which) {
                 context->context = mac_gl_init(MAC_GL_PROFILE_LEGACY);
                 context->legacy = TRUE;
         }
-#else // WIN32
+#else // _WIN32
         if(which == GL_CONTEXT_ANY) {
                 context->context = win32_context_init(OPENGL_VERSION_UNSPECIFIED);
         } else if(which == GL_CONTEXT_LEGACY) {
@@ -250,4 +248,3 @@ void gl_context_make_current(struct gl_context *context)
 #endif
 }
 
-#endif /* defined HAVE_MACOSX || (defined HAVE_LINUX && defined HAVE_LIBGLEW) */
diff --git a/src/host.cpp b/src/host.cpp
index 4139d05e1..ee18d7e5f 100644
--- a/src/host.cpp
+++ b/src/host.cpp
@@ -47,7 +47,7 @@
 #ifndef _WIN32
 #include <execinfo.h>
 #include <fcntl.h>
-#endif // defined WIN32
+#endif // defined _WIN32
 
 #if __GLIBC__ == 2 && __GLIBC_MINOR__ < 27
 #include <sys/syscall.h>
@@ -192,7 +192,7 @@ void common_cleanup(struct init_data *init)
         muntrace();
 #endif
 
-#ifdef WIN32
+#ifdef _WIN32
         WSACleanup();
 #endif
 }
@@ -205,7 +205,7 @@ ADD_TO_PARAM("stderr-buf",
          "  Buffering for stderr\n");
 static bool set_output_buffering() {
         const unordered_map<const char *, pair<FILE *, int>> outs = { // pair<output, default mode>
-#ifdef WIN32
+#ifdef _WIN32
                 { "stdout-buf", pair{stdout, _IONBF} },
 #else
                 { "stdout-buf", pair{stdout, _IOLBF} },
@@ -268,7 +268,7 @@ static int x11_error_handler(Display *d, XErrorEvent *e) {
  */
 static void load_libgcc()
 {
-#ifndef WIN32
+#ifndef _WIN32
         array<void *, 1> addresses{};
         backtrace(addresses.data(), addresses.size());
 #endif
@@ -441,7 +441,7 @@ struct init_data *common_preinit(int argc, char *argv[])
 #endif
 
         struct init_data init{};
-#ifdef WIN32
+#ifdef _WIN32
         WSADATA wsaData;
         int err = WSAStartup(MAKEWORD(2, 2), &wsaData);
         if(err != 0) {
@@ -1200,7 +1200,7 @@ print_backtrace()
                 }
         }
         close(fd);
-#endif // defined WIN32
+#endif // defined _WIN32
 }
 
 void crash_signal_handler(int sig)
@@ -1229,12 +1229,12 @@ void crash_signal_handler(int sig)
 void hang_signal_handler(int sig)
 {
         UNUSED(sig);
-#ifndef WIN32
+#ifndef _WIN32
         assert(sig == SIGALRM);
         char msg[] = "Hang detected - you may continue waiting or kill UltraGrid. Please report if UltraGrid doesn't exit after reasonable amount of time.\n";
         write_all(STDERR_FILENO, sizeof msg - 1, msg);
         signal(SIGALRM, SIG_DFL);
-#endif // ! defined WIN32
+#endif // ! defined _WIN32
 }
 
 // some common parameters used within multiple modules
diff --git a/src/ihdtv/ihdtv.c b/src/ihdtv/ihdtv.c
index 014d305a9..8a66ba2b8 100644
--- a/src/ihdtv/ihdtv.c
+++ b/src/ihdtv/ihdtv.c
@@ -52,7 +52,7 @@
 #include "config_win32.h"
 #endif // HAVE_CONFIG_H
 
-#ifndef WIN32
+#ifndef _WIN32
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -513,5 +513,5 @@ ihdtv_receive(ihdtv_connection * connection, char *buffer,
         return 0;
 }
 
-#endif // WIN32
+#endif // _WIN32
 
diff --git a/src/ihdtv/ihdtv.h b/src/ihdtv/ihdtv.h
index 7803dac6a..7eb1dec95 100644
--- a/src/ihdtv/ihdtv.h
+++ b/src/ihdtv/ihdtv.h
@@ -52,7 +52,7 @@
 #include "config_win32.h"
 #endif // HAVE_CONFIG_H
 
-#ifndef WIN32
+#ifndef _WIN32
 
 #ifndef _IHDTV_H_
 #define _IHDTV_H_
@@ -130,5 +130,5 @@ ihdtv_send(ihdtv_connection *tx_connection, struct video_frame *tx_frame, unsign
 
 #endif
 
-#endif // WIN32
+#endif // _WIN32
 
diff --git a/src/keyboard_control.cpp b/src/keyboard_control.cpp
index 314d0e3e8..5829e43d9 100644
--- a/src/keyboard_control.cpp
+++ b/src/keyboard_control.cpp
@@ -346,7 +346,7 @@ static int64_t get_ansi_code() {
         return c;
 }
 
-#ifndef WIN32
+#ifndef _WIN32
 /*
  * Input must be 0x80-0xff
  */
@@ -381,7 +381,7 @@ static int64_t get_utf8_code(int c) {
 }
 #endif
 
-#ifdef WIN32
+#ifdef _WIN32
 static int64_t convert_win_to_ansi_keycode(int c) {
         switch (c) {
         case 0xe048: return K_UP;
@@ -397,7 +397,7 @@ static int64_t convert_win_to_ansi_keycode(int c) {
 #endif
 
 static bool is_utf8(int64_t ch) {
-#ifdef WIN32
+#ifdef _WIN32
         return false;
 #endif
 
@@ -502,7 +502,7 @@ int64_t keyboard_control::impl::get_next_key()
                                 if ((c = get_ansi_code()) < 0) {
                                         continue;
                                 }
-#ifdef WIN32
+#ifdef _WIN32
                         } else if (c == 0x0 || c == 0xe0) { // Win keycodes
                                 int tmp = GETCH();
                                 debug_msg(MOD_NAME "Pressed %d\n", tmp);
diff --git a/src/main.cpp b/src/main.cpp
index e68a41c00..c2a3f5725 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -67,7 +67,7 @@
 #include <cstdlib>
 #ifndef _WIN32
 #include <execinfo.h>
-#endif // defined WIN32
+#endif // defined _WIN32
 #include <getopt.h>
 #include <iostream>
 #include <list>
@@ -1253,7 +1253,7 @@ int main(int argc, char *argv[])
 
         struct ug_nat_traverse *nat_traverse = nullptr;
 
-#ifndef WIN32
+#ifndef _WIN32
         signal(SIGQUIT, crash_signal_handler);
 #endif
         signal(SIGABRT, crash_signal_handler);
@@ -1361,7 +1361,7 @@ int main(int argc, char *argv[])
 
         signal(SIGINT, signal_handler);
         signal(SIGTERM, signal_handler);
-#ifndef WIN32
+#ifndef _WIN32
         signal(SIGHUP, signal_handler);
         signal(SIGPIPE, signal_handler);
 #endif
@@ -1535,7 +1535,7 @@ cleanup:
 
         signal(SIGINT, SIG_DFL);
         signal(SIGTERM, SIG_DFL);
-#ifndef WIN32
+#ifndef _WIN32
         signal(SIGHUP, SIG_DFL);
         signal(SIGALRM, hang_signal_handler);
 #endif
diff --git a/src/rtp/ldgm.cpp b/src/rtp/ldgm.cpp
index 9830046f9..3b6fc85fb 100644
--- a/src/rtp/ldgm.cpp
+++ b/src/rtp/ldgm.cpp
@@ -172,7 +172,7 @@ void ldgm::set_params(unsigned int k, unsigned int m, unsigned int c, unsigned i
 
         int res;
 
-#ifdef WIN32
+#ifdef _WIN32
         TCHAR tmpPath[MAX_PATH];
         UINT ret = GetTempPath(MAX_PATH, tmpPath);
         if(ret == 0 || ret > MAX_PATH) {
diff --git a/src/rtp/net_udp.c b/src/rtp/net_udp.c
index 49474dc93..7744aa62d 100644
--- a/src/rtp/net_udp.c
+++ b/src/rtp/net_udp.c
@@ -84,7 +84,7 @@ static void *udp_reader(void *arg);
 const struct in6_addr in6addr_any = { IN6ADDR_ANY_INIT };
 #endif
 
-#ifdef WIN32
+#ifdef _WIN32
 typedef char *sockopt_t;
 #else
 typedef void *sockopt_t;
@@ -145,7 +145,7 @@ struct socket_udp_local {
         fd_t rx_fd;
         fd_t tx_fd;
         bool multithreaded;
-#ifdef WIN32
+#ifdef _WIN32
         bool is_wsa_overlapped;
 #endif
 
@@ -172,7 +172,7 @@ struct _socket_udp {
         struct socket_udp_local *local;
         bool local_is_slave; // whether is the local
 
-#ifdef WIN32
+#ifdef _WIN32
         WSAOVERLAPPED *overlapped;
         WSAEVENT *overlapped_events;
         void **dispose_udata;
@@ -184,7 +184,7 @@ struct _socket_udp {
 
 static void udp_clean_async_state(socket_udp *s);
 
-#ifdef WIN32
+#ifdef _WIN32
 /* Want to use both Winsock 1 and 2 socket options, but since
 * IPv6 support requires Winsock 2 we have to add own backwards
 * compatibility for Winsock 1.
@@ -192,7 +192,7 @@ static void udp_clean_async_state(socket_udp *s);
 #define SETSOCKOPT winsock_versions_setsockopt
 #else
 #define SETSOCKOPT setsockopt
-#endif                          /* WIN32 */
+#endif                          /* _WIN32 */
 
 #define GETSOCKOPT getsockopt
 
@@ -205,7 +205,7 @@ void socket_error(const char *msg, ...)
         va_list ap;
         char buffer[ERRBUF_SIZE] = "";
 
-#ifdef WIN32
+#ifdef _WIN32
 #define WSERR(x) {#x,x}
         struct wse {
                 char errname[20];
@@ -254,7 +254,7 @@ void socket_error(const char *msg, ...)
 #endif
 }
 
-#ifdef WIN32
+#ifdef _WIN32
 #define socket_herror socket_error
 #else
 static void socket_herror(const char *msg, ...)
@@ -270,7 +270,7 @@ static void socket_herror(const char *msg, ...)
 }
 #endif
 
-#ifdef WIN32
+#ifdef _WIN32
 /* ws2tcpip.h defines these constants with different values from
 * winsock.h so files that use winsock 2 values but try to use 
 * winsock 1 fail.  So what was the motivation in changing the
@@ -367,7 +367,7 @@ static bool udp_addr_valid4(const char *dst)
 static bool udp_join_mcast_grp4(unsigned long addr, int rx_fd, int tx_fd, int ttl, unsigned int ifindex)
 {
         if (IN_MULTICAST(ntohl(addr))) {
-#ifndef WIN32
+#ifndef _WIN32
                 char loop = 1;
 #endif
                 struct ip_mreq imr;
@@ -381,7 +381,7 @@ static bool udp_join_mcast_grp4(unsigned long addr, int rx_fd, int tx_fd, int tt
                         socket_error("setsockopt IP_ADD_MEMBERSHIP");
                         return false;
                 }
-#ifndef WIN32
+#ifndef _WIN32
                 if (SETSOCKOPT
                     (tx_fd, IPPROTO_IP, IP_MULTICAST_LOOP, &loop,
                      sizeof(loop)) != 0) {
@@ -750,7 +750,7 @@ static bool set_sock_opts_and_bind(fd_t fd, bool ipv6, uint16_t rx_port, int ttl
         }
         if (bind(fd, (struct sockaddr *)&s_in, sin_len) != 0) {
                 socket_error("bind");
-#ifdef WIN32
+#ifdef _WIN32
                 log_msg(LOG_LEVEL_ERROR, "Check if there is no service running on UDP port %d. ", rx_port);
                 if (rx_port == 5004 || rx_port == 5005)
                         log_msg(LOG_LEVEL_ERROR, "Windows Media Services is usually a good candidate to check and disable.\n");
@@ -764,7 +764,7 @@ static bool set_sock_opts_and_bind(fd_t fd, bool ipv6, uint16_t rx_port, int ttl
 ADD_TO_PARAM("udp-queue-len",
                 "* udp-queue-len=<l>\n"
                 "  Use different queue size than default DEFAULT_MAX_UDP_READER_QUEUE_LEN\n");
-#ifdef WIN32
+#ifdef _WIN32
 ADD_TO_PARAM("udp-disable-multi-socket",
                 "* udp-disable-multi-socket\n"
                 "  Disable separate sockets for RX and TX (Win only). Separated RX/TX is a workaround\n"
@@ -818,7 +818,7 @@ socket_udp *udp_init_if(const char *addr, const char *iface, uint16_t rx_port,
         } else {
                 s->ifindex = 0;
         }
-#ifdef WIN32
+#ifdef _WIN32
         if (!is_host_loopback(addr)) {
                 s->local->is_wsa_overlapped = true;
         }
@@ -1040,7 +1040,7 @@ int udp_sendto(socket_udp * s, char *buffer, int buflen, struct sockaddr *dst_ad
         return sendto(s->local->tx_fd, buffer, buflen, 0, dst_addr, addrlen);
 }
 
-#ifdef WIN32
+#ifdef _WIN32
 int udp_sendv(socket_udp * s, LPWSABUF vector, int count, void *d)
 {
         assert(s != NULL);
@@ -1083,7 +1083,7 @@ int udp_sendv(socket_udp * s, struct iovec *vector, int count, void *d)
         free(d);
         return ret;
 }
-#endif // WIN32
+#endif // _WIN32
 
 /**
  * When receiving data in separate thread, this function fetches data
@@ -1282,7 +1282,7 @@ int udp_recv_data(socket_udp * s, char **buffer){
         return udp_recvfrom_data(s, buffer, NULL, NULL);
 }
 
-#ifndef WIN32
+#ifndef _WIN32
 int udp_recvv(socket_udp * s, struct msghdr *m)
 {
         if (recvmsg(s->local->rx_fd, m, 0) == -1) {
@@ -1291,7 +1291,7 @@ int udp_recvv(socket_udp * s, struct msghdr *m)
         }
         return 0;
 }
-#endif // WIN32
+#endif // _WIN32
 
 /**
  * udp_fd_set:
@@ -1529,7 +1529,7 @@ void udp_flush_recv_buf(socket_udp *s)
  */
 void udp_async_start(socket_udp *s, int nr_packets)
 {
-#ifdef WIN32
+#ifdef _WIN32
         if (!s->local->is_wsa_overlapped) {
                 return;
         }
@@ -1556,7 +1556,7 @@ void udp_async_start(socket_udp *s, int nr_packets)
 
 void udp_async_wait(socket_udp *s)
 {
-#ifdef WIN32
+#ifdef _WIN32
         if (!s->overlapping_active)
                 return;
         for(int i = 0; i < s->overlapped_count; i += WSA_MAXIMUM_WAIT_EVENTS)
@@ -1583,7 +1583,7 @@ void udp_async_wait(socket_udp *s)
 
 static void udp_clean_async_state(socket_udp *s)
 {
-#ifdef WIN32
+#ifdef _WIN32
         for (int i = 0; i < s->overlapped_max; i++) {
                 WSACloseEvent(s->overlapped[i].hEvent);
         }
@@ -1679,7 +1679,7 @@ int udp_port_pair_is_free(int force_ip_version, int even_port)
         return 0;
 }
 
-#ifdef WIN32
+#ifdef _WIN32
 /**
  * This function sends buffer asynchronously with provided Winsock parameters.
  *
diff --git a/src/rtp/net_udp.h b/src/rtp/net_udp.h
index ac1e506b1..7898ab527 100644
--- a/src/rtp/net_udp.h
+++ b/src/rtp/net_udp.h
@@ -78,7 +78,7 @@ int         udp_sendto(socket_udp *s, char *buffer, int buflen, struct sockaddr
 int         udp_recvv(socket_udp *s, struct msghdr *m);
 void        udp_async_start(socket_udp *s, int nr_packets);
 void        udp_async_wait(socket_udp *s);
-#ifdef WIN32
+#ifdef _WIN32
 int         udp_sendv(socket_udp *s, LPWSABUF vector, int count, void *d);
 #else
 int         udp_sendv(socket_udp *s, struct iovec *vector, int count, void *d);
@@ -116,7 +116,7 @@ bool        udp_is_ipv6(socket_udp *s);
 
 void        socket_error(const char *msg, ...);
 
-#ifdef WIN32
+#ifdef _WIN32
 int         udp_send_wsa_async(socket_udp *s, char *buffer, int buflen, LPWSAOVERLAPPED_COMPLETION_ROUTINE, LPWSAOVERLAPPED);
 int         udp_sendto_wsa_async(socket_udp *s, char *buffer, int buflen, LPWSAOVERLAPPED_COMPLETION_ROUTINE l, LPWSAOVERLAPPED o, struct sockaddr *addr, socklen_t addrlen);
 #endif
diff --git a/src/rtp/rtp.c b/src/rtp/rtp.c
index 913939bf6..685f90b4f 100644
--- a/src/rtp/rtp.c
+++ b/src/rtp/rtp.c
@@ -914,7 +914,7 @@ static char *get_cname(socket_udp * s)
         char *hname;
         char *uname;
         char *cname;
-#ifndef WIN32
+#ifndef _WIN32
         struct passwd *pwent;
 #else
         char *name;
@@ -925,7 +925,7 @@ static char *get_cname(socket_udp * s)
         cname[0] = '\0';
 
         /* First, fill in the username... */
-#ifdef WIN32
+#ifdef _WIN32
         name = NULL;
         namelen = 0;
         GetUserName(NULL, &namelen);
@@ -1046,7 +1046,7 @@ struct rtp *rtp_init_if(const char *addr, const char *iface,
         char *cname;
         char *hname;
 
-#ifdef WIN32
+#ifdef _WIN32
         if (multithreaded) {
                 log_msg(LOG_LEVEL_WARNING, "Multithreaded RTP is not recommended for MSW due to internal locking within Winsock implementation.\n");
         }
@@ -2766,7 +2766,7 @@ rtp_send_data_hdr(struct rtp *session,
         uint8_t *buffer = NULL;
         rtp_packet *packet = NULL;
         uint8_t initVec[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
-#ifdef WIN32
+#ifdef _WIN32
         WSABUF *send_vector = NULL;
 #else
         struct iovec send_vector[3];
@@ -2818,7 +2818,7 @@ rtp_send_data_hdr(struct rtp *session,
         /* Allocate memory for the packet... */
         assert(buffer_len < RTP_MAX_PACKET_LEN);
         /* we dont always need 20 (12|16) but this seems to work. LG */
-#ifdef WIN32
+#ifdef _WIN32
         d = (uint8_t *) malloc(3 * sizeof(WSABUF) + 20 + RTP_PACKET_HEADER_SIZE);
         send_vector = d;
         buffer = (uint8_t *) d + 3 * sizeof(WSABUF);
@@ -2827,7 +2827,7 @@ rtp_send_data_hdr(struct rtp *session,
 #endif
         packet = (rtp_packet *)(void *) buffer;
 
-#ifdef WIN32
+#ifdef _WIN32
         send_vector[0].buf = (char *) (buffer + RTP_PACKET_HEADER_SIZE);
         send_vector[0].len = buffer_len;
 #else
@@ -2883,7 +2883,7 @@ rtp_send_data_hdr(struct rtp *session,
         }
         /* ...the payload header... */
         if (phdr != NULL) {
-#ifdef WIN32
+#ifdef _WIN32
                 send_vector[send_vector_len].buf = phdr;
                 send_vector[send_vector_len].len = phdr_len;
 #else
@@ -2894,7 +2894,7 @@ rtp_send_data_hdr(struct rtp *session,
         }
         /* ...and the media data... */
         if (data_len > 0) {
-#ifdef WIN32
+#ifdef _WIN32
                 send_vector[send_vector_len].buf = (void *) data;
                 send_vector[send_vector_len].len = data_len;
 #else
diff --git a/src/utils/fs.c b/src/utils/fs.c
index 384b00db9..eaffdc266 100644
--- a/src/utils/fs.c
+++ b/src/utils/fs.c
@@ -61,7 +61,7 @@ const char *get_temp_dir(void)
                 return temp_dir;
         }
 
-#ifdef WIN32
+#ifdef _WIN32
         if (GetTempPathA(sizeof temp_dir, temp_dir) == 0) {
                 return NULL;
         }
diff --git a/src/utils/misc.cpp b/src/utils/misc.cpp
index 0642f101a..999108d12 100644
--- a/src/utils/misc.cpp
+++ b/src/utils/misc.cpp
@@ -168,7 +168,7 @@ const char *format_in_si_units(unsigned long long int val) {
 
 
 bool is_wine() {
-#ifdef WIN32
+#ifdef _WIN32
         HMODULE hntdll = GetModuleHandle("ntdll.dll");
         if(!hntdll) {
                 return false;
diff --git a/src/utils/nat.c b/src/utils/nat.c
index db10436f6..751e637a4 100644
--- a/src/utils/nat.c
+++ b/src/utils/nat.c
@@ -160,7 +160,7 @@ static const char* decode_fresult(pcp_fstate_e s)
     }
 }
 
-#ifdef WIN32
+#ifdef _WIN32
 static char *ctime_r(const time_t *timep, char *buf)
 {
     ctime_s(buf, 26, timep);
diff --git a/src/utils/net.c b/src/utils/net.c
index 923c876fa..81897e084 100644
--- a/src/utils/net.c
+++ b/src/utils/net.c
@@ -308,7 +308,7 @@ bool get_local_addresses(struct sockaddr_storage *addrs, size_t *len, int ip_ver
 	}
 
 	return true;
-#else // ! defined WIN32
+#else // ! defined _WIN32
 	size_t available_len = *len;
 	*len = 0;
 	struct ifaddrs* a = NULL;
diff --git a/src/utils/net.h b/src/utils/net.h
index cf2162a5e..dffe59822 100644
--- a/src/utils/net.h
+++ b/src/utils/net.h
@@ -71,7 +71,7 @@ unsigned get_sockaddr_addr_port(struct sockaddr *sa);
 const char *get_sockaddr_str(struct sockaddr *sa);
 const char *ug_gai_strerror(int errcode);
 
-#ifdef WIN32
+#ifdef _WIN32
 #define CLOSESOCKET closesocket
 #else
 #define CLOSESOCKET close
diff --git a/src/utils/thread.c b/src/utils/thread.c
index e4a917324..6f2f0aaca 100644
--- a/src/utils/thread.c
+++ b/src/utils/thread.c
@@ -53,7 +53,7 @@
 #include "host.h"
 #include "utils/thread.h"
 
-#if ! defined  WIN32 || defined HAVE_SETTHREADDESCRIPTION
+#if ! defined  _WIN32 || defined HAVE_SETTHREADDESCRIPTION
 static inline char *get_argv_program_name(void) {
 #ifdef HAVE_CONFIG_H
         if (uv_argv != NULL && uv_argv[0] != NULL) {
diff --git a/src/video_capture/bluefish444.cpp b/src/video_capture/bluefish444.cpp
index e17805821..7b863f7a6 100644
--- a/src/video_capture/bluefish444.cpp
+++ b/src/video_capture/bluefish444.cpp
@@ -73,7 +73,7 @@ static void *worker(void *arg);
 static void show_help(void);
 static void WaitForMajorInterrupt(struct vidcap_bluefish444_state *s);
 static void SyncForSignal(struct vidcap_bluefish444_state *s);
-#ifdef WIN32
+#ifdef _WIN32
 static int CompleteBlueAsyncReq(HANDLE hDevice, LPOVERLAPPED pOverlap);
 #endif
 static bool should_exit_worker = false;
@@ -162,7 +162,7 @@ struct vidcap_bluefish444_state {
         uint32_t                  MemoryFormat;
         uint32_t                  UpdateFormat;
         bool                      SubField;
-#ifdef WIN32
+#ifdef _WIN32
         blue_video_sync_struct   *pIrqInfo;
 #endif
 
@@ -173,7 +173,7 @@ struct vidcap_bluefish444_state {
         struct audio_frame        audio;
         unsigned int             *hanc_buffer;
 
-#ifdef WIN32
+#ifdef _WIN32
         OVERLAPPED                OverlapChA;
 #endif
 
@@ -262,7 +262,7 @@ bool UpdateVideoMode(struct vidcap_bluefish444_state *s, uint32_t VideoMode)
         return false;
 }
 
-#ifdef WIN32
+#ifdef _WIN32
 static int CompleteBlueAsyncReq(HANDLE hDevice, LPOVERLAPPED pOverlap)
 {
         DWORD bytesReturned;
@@ -275,7 +275,7 @@ static int CompleteBlueAsyncReq(HANDLE hDevice, LPOVERLAPPED pOverlap)
 
 static void WaitForMajorInterrupt(struct vidcap_bluefish444_state *s)
 {
-#ifdef WIN32
+#ifdef _WIN32
         assert(s->attachedDevices == 1);
 
         BOOL bWaitForField = TRUE;
@@ -505,7 +505,7 @@ static void *worker(void *arg)
                         }
 
                 } else {
-#ifdef WIN32
+#ifdef _WIN32
                         DWORD IrqReturn = 0;
                         UINT VideoMsc = 0;
                         // we do not allow mode change when in subfield mode
@@ -608,7 +608,7 @@ static void *worker(void *arg)
                 pthread_mutex_unlock(&s->lock);
 
                 if(s->VideoEngine == VIDEO_ENGINE_DUPLEX) {
-#ifdef WIN32
+#ifdef _WIN32
                         unsigned int FifoSize = 0;
                         if(BLUE_FAIL(bfcGetCaptureVideoFrameInfoEx(s->pSDK[0], &s->OverlapChA, FrameInfo,
                                                         0, &FifoSize))) {
@@ -656,7 +656,7 @@ static void *worker(void *arg)
 
                 //DMA the frame from the card to our buffer
                 for(int i = 0; i < s->attachedDevices; ++i) {
-#ifdef WIN32
+#ifdef _WIN32
                         bfcSystemBufferReadAsync(s->pSDK[i], (unsigned char *)
                                         current_frame->video->tiles[i].data,
                                         ChunkSize, NULL,
@@ -675,7 +675,7 @@ static void *worker(void *arg)
                 }
 
                 if(s->grab_audio && hanc_buffer_id != -1) {
-#ifdef WIN32
+#ifdef _WIN32
                         bfcSystemBufferReadAsync(s->pSDK[0], (unsigned char *) s->hanc_buffer, MAX_HANC_SIZE, NULL, BlueImage_HANC_DMABuffer(BufferId, BLUE_DATA_HANC));
 #else
                         bfcSystemBufferRead(s->pSDK[0], (unsigned char *) s->hanc_buffer, MAX_HANC_SIZE, BlueImage_HANC_DMABuffer(BufferId, BLUE_DATA_HANC), 0);
@@ -815,7 +815,7 @@ vidcap_bluefish444_init(struct vidcap_params *params, void **state)
         parse_fmt(s, tmp_fmt);
         free(tmp_fmt);
 
-#ifdef WIN32
+#ifdef _WIN32
         memset(&s->OverlapChA, 0, sizeof(s->OverlapChA));
         s->OverlapChA.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
 #endif
@@ -824,7 +824,7 @@ vidcap_bluefish444_init(struct vidcap_params *params, void **state)
         s->SavedVideoMode = VID_FMT_INVALID;
 
         if(s->SubField) {
-#ifdef WIN32
+#ifdef _WIN32
                 s->VideoEngine = VIDEO_ENGINE_FRAMESTORE;
                 s->pIrqInfo = bfcNewVideoSyncStruct(s->pSDK);
 #else
@@ -991,7 +991,7 @@ static void vidcap_bluefish444_done(void *state)
         pthread_mutex_unlock(&s->lock);
         pthread_join(s->worker_id, NULL);
 
-#ifdef WIN32
+#ifdef _WIN32
         CloseHandle(s->OverlapChA.hEvent);
 #endif
 
diff --git a/src/video_capture/decklink.cpp b/src/video_capture/decklink.cpp
index a01b8f17e..2409875a5 100644
--- a/src/video_capture/decklink.cpp
+++ b/src/video_capture/decklink.cpp
@@ -83,7 +83,7 @@ constexpr const int DEFAULT_AUDIO_BPS = 4;
 constexpr const size_t MAX_AUDIO_PACKETS = 10;
 #define MOD_NAME "[DeckLink capture] "
 
-#ifndef WIN32
+#ifndef _WIN32
 #define STDMETHODCALLTYPE
 #endif
 
diff --git a/src/video_capture/deltacast.cpp b/src/video_capture/deltacast.cpp
index 1c037c2b8..1a20ff927 100644
--- a/src/video_capture/deltacast.cpp
+++ b/src/video_capture/deltacast.cpp
@@ -45,7 +45,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#ifndef WIN32
+#ifndef _WIN32
 #include <sys/ioctl.h>
 #include <sys/poll.h>
 #endif
diff --git a/src/video_capture/deltacast_dvi.cpp b/src/video_capture/deltacast_dvi.cpp
index 5908be30e..c5ab22e7d 100644
--- a/src/video_capture/deltacast_dvi.cpp
+++ b/src/video_capture/deltacast_dvi.cpp
@@ -46,7 +46,7 @@
 #include <unistd.h>
 #include <string.h>
 #include <sys/stat.h>
-#ifndef WIN32
+#ifndef _WIN32
 #include <sys/poll.h>
 #include <sys/ioctl.h>
 #endif
diff --git a/src/video_capture/import.c b/src/video_capture/import.c
index eeeaa7255..348e7a355 100644
--- a/src/video_capture/import.c
+++ b/src/video_capture/import.c
@@ -859,7 +859,7 @@ static void *video_reader_callback(void *arg)
                 struct stat sb;
 
                 int flags = O_RDONLY;
-#ifdef WIN32
+#ifdef _WIN32
                 flags |= O_BINARY;
 #endif
                 if (data->o_direct) {
diff --git a/src/video_display/bluefish444.cpp b/src/video_display/bluefish444.cpp
index 0329052df..45cb93cc5 100644
--- a/src/video_display/bluefish444.cpp
+++ b/src/video_display/bluefish444.cpp
@@ -264,7 +264,7 @@ void *display_bluefish444_state::playback_loop() noexcept
 
         gettimeofday(&t0, NULL);
 
-#ifdef WIN32
+#ifdef _WIN32
         OVERLAPPED Overlapped[MAX_BLUE_OUT_CHANNELS];
         for (int i = 0;i < MAX_BLUE_OUT_CHANNELS; ++ i) {
                 Overlapped[i].hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
@@ -303,7 +303,7 @@ void *display_bluefish444_state::playback_loop() noexcept
 
                 for(int i = 0; i < m_AttachedDevicesCount; ++i) {
                         unsigned char *videoBuffer;
-#ifdef WIN32
+#ifdef _WIN32
                         OVERLAPPED *OverlapCh = &Overlapped[i];
 #endif
                         if(m_TileCount == m_AttachedDevicesCount) {
@@ -311,13 +311,13 @@ void *display_bluefish444_state::playback_loop() noexcept
                         } else { // untiled 4K
                                 videoBuffer = (unsigned char *) frame->pVideoBuffer[0];
                         }
-#ifdef WIN32
+#ifdef _WIN32
                         int err = bfcSystemBufferWriteAsync(
 #else
                         int err = bfcSystemBufferWrite(
 #endif
                                         m_pSDK[i], videoBuffer + m_Offset[i], m_GoldenSize,
-#ifdef WIN32
+#ifdef _WIN32
                                         OverlapCh,
 #endif
                                         (m_PlayAudio && i == 0 ?
@@ -329,7 +329,7 @@ void *display_bluefish444_state::playback_loop() noexcept
                                 WaitResult = false;
                         }
                 }
-#ifdef WIN32
+#ifdef _WIN32
                 if(WaitResult) {
                         for(int i = 0; i < m_AttachedDevicesCount; ++i) {
                                 DWORD BytesReturned = 0;
@@ -396,7 +396,7 @@ void *display_bluefish444_state::playback_loop() noexcept
                                 //ResetEvent(OverlapChA.hEvent);
 
                                 //now we can DMA the HANC frame
-#ifdef WIN32
+#ifdef _WIN32
                                 bfcSystemBufferWriteAsync(m_pSDK[0], (unsigned char *) m_HancInfo.hanc_data_ptr,
                                                 MAX_HANC_SIZE,
                                                 NULL, BlueImage_HANC_DMABuffer(frame->BufferId, BLUE_DATA_HANC));
@@ -441,7 +441,7 @@ void *display_bluefish444_state::playback_loop() noexcept
                 m_pPlayingBuffer = frame;
         }
 
-#ifdef WIN32
+#ifdef _WIN32
                 for(int i = 0; i < m_AttachedDevicesCount; ++i) {
                         CloseHandle(Overlapped[i].hEvent);
                 }
diff --git a/src/video_display/decklink.cpp b/src/video_display/decklink.cpp
index 2646e9796..fd4faf0a5 100644
--- a/src/video_display/decklink.cpp
+++ b/src/video_display/decklink.cpp
@@ -80,7 +80,7 @@
 #include "video_display.h"
 #include "video_display/decklink_drift_fix.hpp"
 
-#ifndef WIN32
+#ifndef _WIN32
 #define STDMETHODCALLTYPE
 #endif
 
@@ -1742,7 +1742,7 @@ static bool display_decklink_reconfigure_audio(void *state, int quant_samples, i
         return true;
 }
 
-#ifndef WIN32
+#ifndef _WIN32
 static bool operator==(const REFIID & first, const REFIID & second){
     return (first.byte0 == second.byte0) &&
         (first.byte1 == second.byte1) &&
diff --git a/src/video_display/opengl_utils.hpp b/src/video_display/opengl_utils.hpp
index 88ef02723..1298d6aea 100644
--- a/src/video_display/opengl_utils.hpp
+++ b/src/video_display/opengl_utils.hpp
@@ -49,7 +49,7 @@
 #       include <X11/Xlib.h>
 #       include <GL/glew.h>
 #       include <GL/glx.h>
-#else // WIN32
+#else // _WIN32
 #       include <GL/glew.h>
 #endif //HAVE_MACOSX
 
diff --git a/src/video_display/openxr_gl.cpp b/src/video_display/openxr_gl.cpp
index 7f7c3d71f..abc0dfd4a 100644
--- a/src/video_display/openxr_gl.cpp
+++ b/src/video_display/openxr_gl.cpp
@@ -53,7 +53,7 @@
 #       include <GL/glx.h>
 #       define XR_USE_PLATFORM_XLIB
 #       define XR_USE_GRAPHICS_API_OPENGL
-#elif defined WIN32
+#elif defined _WIN32
 #       define XR_USE_PLATFORM_WIN32
 #       define XR_USE_GRAPHICS_API_OPENGL
 #endif
@@ -629,7 +629,7 @@ static void display_xrgl_run(void *state){
         Openxr_session session(s->xr_state.instance.get(),
                         s->xr_state.system_id,
                         &graphics_binding_gl);
-#elif defined WIN32
+#elif defined _WIN32
         XrGraphicsBindingOpenGLWin32KHR graphics_binding_gl = {};
         graphics_binding_gl.type = XR_TYPE_GRAPHICS_BINDING_OPENGL_WIN32_KHR;
         graphics_binding_gl.next = nullptr;
diff --git a/src/video_display/sdl_window.hpp b/src/video_display/sdl_window.hpp
index c94909d55..9641197bb 100644
--- a/src/video_display/sdl_window.hpp
+++ b/src/video_display/sdl_window.hpp
@@ -49,7 +49,7 @@
 #       include <X11/Xlib.h>
 #       include <GL/glew.h>
 #       include <GL/glx.h>
-#else // WIN32
+#else // _WIN32
 #       include <GL/glew.h>
 #endif //HAVE_MACOSX
 
diff --git a/src/video_rxtx/rtp.cpp b/src/video_rxtx/rtp.cpp
index adb0a0378..9ecd9bc9c 100644
--- a/src/video_rxtx/rtp.cpp
+++ b/src/video_rxtx/rtp.cpp
@@ -242,7 +242,7 @@ void rtp_video_rxtx::display_buf_increase_warning(int size)
 {
         log_msg(LOG_LEVEL_INFO, "\n***\n"
                         "Unable to set buffer size to %d B.\n"
-#if defined WIN32
+#if defined _WIN32
                         "See https://github.com/CESNET/UltraGrid/wiki/Extending-Network-Buffers-%%28Windows%%29 for details.\n",
 #else
                         "Please set net.core.rmem_max value to %d or greater (see also\n"
@@ -259,7 +259,7 @@ void rtp_video_rxtx::display_buf_increase_warning(int size)
 #ifdef HAVE_MACOSX
                         size * 4,
 #endif /* HAVE_MACOSX */
-#endif /* ! defined WIN32 */
+#endif /* ! defined _WIN32 */
                         size);
 
 }
@@ -270,7 +270,7 @@ struct rtp *rtp_video_rxtx::initialize_network(const char *addr, int recv_port,
 {
         double rtcp_bw = 5 * 1024 * 1024;       /* FIXME */
 
-#if !defined WIN32
+#if !defined _WIN32
         const bool multithreaded = true;
 #else
         const bool multithreaded = false;