diff --git a/src/apps/deskflow-core/deskflow-core.cpp b/src/apps/deskflow-core/deskflow-core.cpp
index 4e1195fc2..285e259d5 100644
--- a/src/apps/deskflow-core/deskflow-core.cpp
+++ b/src/apps/deskflow-core/deskflow-core.cpp
@@ -9,6 +9,7 @@
 #include "arch/Arch.h"
 #include "base/EventQueue.h"
 #include "base/Log.h"
+#include "common/ExitCodes.h"
 #include "deskflow/ClientApp.h"
 #include "deskflow/ServerApp.h"
 
@@ -61,7 +62,7 @@ int main(int argc, char **argv)
 
   if (isHelp(argc, argv)) {
     showHelp();
-    return 0;
+    return s_exitSuccess;
   }
 
   // Create a shared memory segment with a unique key
@@ -76,7 +77,7 @@ int main(int argc, char **argv)
   // If we can create 1 byte of SHM we are the only instance
   if (!sharedMemory.create(1)) {
     LOG_WARN("an instance of deskflow core (server or client) is already running");
-    return 0;
+    return s_exitDuplicate;
   }
 #if SYSAPI_WIN32
   // HACK to make sure settings gets the correct qApp path
@@ -98,5 +99,5 @@ int main(int argc, char **argv)
     showHelp();
   }
 
-  return 0;
+  return s_exitSuccess;
 }
diff --git a/src/apps/deskflow-daemon/deskflow-daemon.cpp b/src/apps/deskflow-daemon/deskflow-daemon.cpp
index 0aa8f3bbe..2c0730b8b 100644
--- a/src/apps/deskflow-daemon/deskflow-daemon.cpp
+++ b/src/apps/deskflow-daemon/deskflow-daemon.cpp
@@ -9,6 +9,7 @@
 #include "arch/Arch.h"
 #include "base/EventQueue.h"
 #include "base/Log.h"
+#include "common/ExitCodes.h"
 #include "common/Settings.h"
 #include "deskflow/DaemonApp.h"
 #include "deskflow/ipc/DaemonIpcServer.h"
diff --git a/src/apps/deskflow-gui/deskflow-gui.cpp b/src/apps/deskflow-gui/deskflow-gui.cpp
index ba1c2bbe1..e40157d96 100644
--- a/src/apps/deskflow-gui/deskflow-gui.cpp
+++ b/src/apps/deskflow-gui/deskflow-gui.cpp
@@ -8,6 +8,7 @@
 
 #include "VersionInfo.h"
 #include "common/Constants.h"
+#include "common/ExitCodes.h"
 #include "common/UrlConstants.h"
 #include "gui/Diagnostic.h"
 #include "gui/DotEnv.h"
@@ -68,18 +69,18 @@ int main(int argc, char *argv[])
 
   if (!parser.errorText().isEmpty()) {
     qCritical().noquote() << parser.errorText() << "\nUse --help for more information.";
-    return 1;
+    return s_exitArgs;
   }
 
   if (parser.isSet(helpOption)) {
     QTextStream(stdout) << kHeader << QStringLiteral("  %1\n\n").arg(kAppDescription)
                         << parser.helpText().replace(QApplication::applicationFilePath(), kAppId);
-    return 0;
+    return s_exitSuccess;
   }
 
   if (parser.isSet(versionOption)) {
     QTextStream(stdout) << kHeader << kCopyright << Qt::endl;
-    return 0;
+    return s_exitSuccess;
   }
 
   // Create a shared memory segment with a unique key
@@ -102,7 +103,7 @@ int main(int argc, char *argv[])
       QMessageBox::information(nullptr, QObject::tr("Deskflow"), QObject::tr("Deskflow is already running"));
     }
     socket.disconnectFromServer();
-    return 0;
+    return s_exitDuplicate;
   }
 
 #if !defined(Q_OS_MAC)
diff --git a/src/lib/common/CMakeLists.txt b/src/lib/common/CMakeLists.txt
index e9556cc24..f39d067c3 100644
--- a/src/lib/common/CMakeLists.txt
+++ b/src/lib/common/CMakeLists.txt
@@ -13,6 +13,7 @@ unset(SERVER_BINARY)
 
 add_library(common STATIC
   Common.h
+  ExitCodes.h
   Settings.h
   Settings.cpp
   QSettingsProxy.cpp
diff --git a/src/lib/common/Common.h b/src/lib/common/Common.h
index 55ecfd58f..8487895c2 100644
--- a/src/lib/common/Common.h
+++ b/src/lib/common/Common.h
@@ -32,9 +32,3 @@
 #else
 #endif
 #endif
-
-static const int s_exitSuccess = 0;    //!< App successfully completed
-static const int s_exitFailed = 1;     //!< App had a general failure
-static const int s_exitTerminated = 2; //!< App was kill by a signal
-static const int s_exitArgs = 3;       //!< App was unable to run due to bad arguments being passed
-static const int s_exitConfig = 4;     //!< App was unable to read the configuration
diff --git a/src/lib/common/ExitCodes.h b/src/lib/common/ExitCodes.h
new file mode 100644
index 000000000..ed5c0ac22
--- /dev/null
+++ b/src/lib/common/ExitCodes.h
@@ -0,0 +1,16 @@
+/*
+ * Deskflow -- mouse and keyboard sharing utility
+ * SPDX-FileCopyrightText: (C) 2025 Deskflow Developers
+ * SPDX-FileCopyrightText: (C) 2010 - 2018, 2024 - 2025 Symless Ltd.
+ * SPDX-FileCopyrightText: (C) 2002 - 2007 Chris Schoeneman
+ * SPDX-License-Identifier: GPL-2.0-only WITH LicenseRef-OpenSSL-Exception
+ */
+
+#pragma once
+
+static const int s_exitSuccess = 0;    //!< App successfully completed
+static const int s_exitFailed = 1;     //!< App had a general failure
+static const int s_exitTerminated = 2; //!< App was kill by a signal
+static const int s_exitArgs = 3;       //!< App was unable to run due to bad arguments being passed
+static const int s_exitConfig = 4;     //!< App was unable to read the configuration
+static const int s_exitDuplicate = 5;  //!< An instance of the app (or core app) is already running
diff --git a/src/lib/deskflow/App.cpp b/src/lib/deskflow/App.cpp
index 3998216e6..ad33d7d9d 100644
--- a/src/lib/deskflow/App.cpp
+++ b/src/lib/deskflow/App.cpp
@@ -13,6 +13,7 @@
 #include "base/Log.h"
 #include "base/LogOutputters.h"
 #include "common/Constants.h"
+#include "common/ExitCodes.h"
 #include "deskflow/ArgsBase.h"
 #include "deskflow/Config.h"
 #include "deskflow/DeskflowException.h"
diff --git a/src/lib/deskflow/ClientApp.cpp b/src/lib/deskflow/ClientApp.cpp
index 2c39c57db..db2f0a754 100644
--- a/src/lib/deskflow/ClientApp.cpp
+++ b/src/lib/deskflow/ClientApp.cpp
@@ -14,6 +14,7 @@
 #include "base/Log.h"
 #include "client/Client.h"
 #include "common/Constants.h"
+#include "common/ExitCodes.h"
 #include "deskflow/ArgParser.h"
 #include "deskflow/ClientArgs.h"
 #include "deskflow/ProtocolTypes.h"
diff --git a/src/lib/deskflow/DaemonApp.cpp b/src/lib/deskflow/DaemonApp.cpp
index dd1816a12..4d8df4d76 100644
--- a/src/lib/deskflow/DaemonApp.cpp
+++ b/src/lib/deskflow/DaemonApp.cpp
@@ -9,6 +9,7 @@
 #include "base/IEventQueue.h"
 #include "base/Log.h"
 #include "base/LogOutputters.h"
+#include "common/ExitCodes.h"
 #include "common/Settings.h"
 #include "deskflow/App.h"
 #include "deskflow/ipc/DaemonIpcServer.h"
diff --git a/src/lib/deskflow/ServerApp.cpp b/src/lib/deskflow/ServerApp.cpp
index 2f9a1f733..ecdf74e81 100644
--- a/src/lib/deskflow/ServerApp.cpp
+++ b/src/lib/deskflow/ServerApp.cpp
@@ -12,6 +12,7 @@
 #include "base/IEventQueue.h"
 #include "base/Log.h"
 #include "base/Path.h"
+#include "common/ExitCodes.h"
 #include "deskflow/App.h"
 #include "deskflow/ArgParser.h"
 #include "deskflow/Screen.h"
diff --git a/src/lib/platform/MSWindowsProcess.cpp b/src/lib/platform/MSWindowsProcess.cpp
index 42e5485da..bd8b8e989 100644
--- a/src/lib/platform/MSWindowsProcess.cpp
+++ b/src/lib/platform/MSWindowsProcess.cpp
@@ -11,6 +11,7 @@
 #include "base/Log.h"
 #include "common/Common.h"
 #include "common/Constants.h"
+#include "common/ExitCodes.h"
 
 #define WIN32_LEAN_AND_MEAN
 #include <Windows.h>