diff --git a/client/browseZeroConf/browse_avahi.cpp b/client/browseZeroConf/browse_avahi.cpp
index a2c1be670..13afbf184 100644
--- a/client/browseZeroConf/browse_avahi.cpp
+++ b/client/browseZeroConf/browse_avahi.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,13 +16,15 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// prototype/interface header file
 #include "browse_avahi.hpp"
+
+// local headers
 #include "common/aixlog.hpp"
 #include "common/snap_exception.hpp"
+
+// standard headers
 #include <cassert>
-#include <cstdio>
-#include <cstdlib>
-#include <ctime>
 #include <iostream>
 
 
diff --git a/client/browseZeroConf/browse_avahi.hpp b/client/browseZeroConf/browse_avahi.hpp
index 6f94b5a29..5507f9c6b 100644
--- a/client/browseZeroConf/browse_avahi.hpp
+++ b/client/browseZeroConf/browse_avahi.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -15,19 +15,21 @@
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
-#ifndef BROWSEAVAHI_H
-#define BROWSEAVAHI_H
 
+#pragma once
+
+class BrowseAvahi;
+
+// local headers
+#include "browse_mdns.hpp"
+
+// 3rd party headers
 #include <avahi-client/client.h>
 #include <avahi-client/lookup.h>
-
 #include <avahi-common/error.h>
 #include <avahi-common/malloc.h>
 #include <avahi-common/simple-watch.h>
 
-class BrowseAvahi;
-
-#include "browse_mdns.hpp"
 
 class BrowseAvahi : public BrowsemDNS
 {
@@ -49,5 +51,3 @@ class BrowseAvahi : public BrowsemDNS
     mDNSResult result_;
     AvahiServiceBrowser* sb_;
 };
-
-#endif
diff --git a/client/browseZeroConf/browse_bonjour.cpp b/client/browseZeroConf/browse_bonjour.cpp
index 91b8ff5d2..d1b34f8cc 100644
--- a/client/browseZeroConf/browse_bonjour.cpp
+++ b/client/browseZeroConf/browse_bonjour.cpp
@@ -1,8 +1,30 @@
+/***
+    This file is part of snapcast
+    Copyright (C) 2014-2024  Johannes Pohl
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+***/
+
+
+// prototype/interface header file
 #include "browse_bonjour.hpp"
 
-#include <deque>
+// local headers
+#include "common/aixlog.hpp"
+
+// standard headers
 #include <iostream>
-#include <memory>
 #ifdef WINDOWS
 #include <WinSock2.h>
 #include <Ws2tcpip.h>
@@ -11,8 +33,6 @@
 #include <sys/socket.h>
 #endif
 
-#include "common/aixlog.hpp"
-#include "common/snap_exception.hpp"
 
 using namespace std;
 
diff --git a/client/browseZeroConf/browse_bonjour.hpp b/client/browseZeroConf/browse_bonjour.hpp
index 509b393d7..e92333c1a 100644
--- a/client/browseZeroConf/browse_bonjour.hpp
+++ b/client/browseZeroConf/browse_bonjour.hpp
@@ -1,15 +1,34 @@
-#ifndef BROWSEBONJOUR_H
-#define BROWSEBONJOUR_H
+/***
+    This file is part of snapcast
+    Copyright (C) 2014-2024  Johannes Pohl
 
-#include <dns_sd.h>
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#pragma once
 
 class BrowseBonjour;
 
+// local headers
 #include "browse_mdns.hpp"
 
+// 3rd party headers
+#include <dns_sd.h>
+
+
 class BrowseBonjour : public BrowsemDNS
 {
 public:
     bool browse(const std::string& serviceName, mDNSResult& result, int timeout) override;
 };
-#endif
diff --git a/client/browseZeroConf/browse_mdns.hpp b/client/browseZeroConf/browse_mdns.hpp
index 66b172b01..45bbedbf6 100644
--- a/client/browseZeroConf/browse_mdns.hpp
+++ b/client/browseZeroConf/browse_mdns.hpp
@@ -1,6 +1,24 @@
-#ifndef BROWSEMDNS_H
-#define BROWSEMDNS_H
+/***
+    This file is part of snapcast
+    Copyright (C) 2014-2024  Johannes Pohl
 
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#pragma once
+
+// standard headers
 #include <string>
 
 enum IPVersion
@@ -37,5 +55,3 @@ using BrowseZeroConf = BrowseAvahi;
 #include "browse_bonjour.hpp"
 using BrowseZeroConf = BrowseBonjour;
 #endif
-
-#endif
diff --git a/client/client_connection.cpp b/client/client_connection.cpp
index 38db84f9b..53825864a 100644
--- a/client/client_connection.cpp
+++ b/client/client_connection.cpp
@@ -21,8 +21,6 @@
 
 // local headers
 #include "common/aixlog.hpp"
-#include "common/message/hello.hpp"
-#include "common/snap_exception.hpp"
 #include "common/str_compat.hpp"
 
 // 3rd party headers
@@ -32,7 +30,6 @@
 
 // standard headers
 #include <iostream>
-#include <mutex>
 
 
 using namespace std;
diff --git a/client/client_connection.hpp b/client/client_connection.hpp
index 9f542f9c6..1a71893cf 100644
--- a/client/client_connection.hpp
+++ b/client/client_connection.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2023  Johannes Pohl
+    Copyright (C) 2014-2024 Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,8 +16,7 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef CLIENT_CONNECTION_HPP
-#define CLIENT_CONNECTION_HPP
+#pragma once
 
 // local headers
 #include "client_settings.hpp"
@@ -32,14 +31,9 @@
 #include <boost/asio/strand.hpp>
 
 // standard headers
-#include <atomic>
-#include <condition_variable>
 #include <deque>
 #include <memory>
-#include <mutex>
-#include <set>
 #include <string>
-#include <thread>
 
 
 using boost::asio::ip::tcp;
@@ -159,7 +153,3 @@ class ClientConnection
     };
     std::deque<PendingMessage> messages_;
 };
-
-
-
-#endif
diff --git a/client/client_settings.hpp b/client/client_settings.hpp
index 2e12cb01d..877216c27 100644
--- a/client/client_settings.hpp
+++ b/client/client_settings.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,15 +16,16 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef CLIENT_SETTINGS_HPP
-#define CLIENT_SETTINGS_HPP
-
-#include <string>
-#include <vector>
+#pragma once
 
+// local headers
 #include "common/sample_format.hpp"
 #include "player/pcm_device.hpp"
 
+// standard headers
+#include <string>
+
+
 
 struct ClientSettings
 {
@@ -79,5 +80,3 @@ struct ClientSettings
     Player player;
     Logging logging;
 };
-
-#endif
diff --git a/client/controller.hpp b/client/controller.hpp
index 2daf90886..27299bf10 100644
--- a/client/controller.hpp
+++ b/client/controller.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2023  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,13 +16,11 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef CONTROLLER_HPP
-#define CONTROLLER_HPP
+#pragma once
 
 // local headers
 #include "client_connection.hpp"
 #include "client_settings.hpp"
-#include "common/message/message.hpp"
 #include "common/message/server_settings.hpp"
 #include "decoder/decoder.hpp"
 #include "player/player.hpp"
@@ -31,8 +29,7 @@
 // 3rd party headers
 
 // standard headers
-#include <atomic>
-#include <thread>
+
 
 using namespace std::chrono_literals;
 
@@ -75,6 +72,3 @@ class Controller
     std::unique_ptr<msg::ServerSettings> serverSettings_;
     std::unique_ptr<msg::CodecHeader> headerChunk_;
 };
-
-
-#endif
diff --git a/client/decoder/flac_decoder.cpp b/client/decoder/flac_decoder.cpp
index 967585a60..930abe308 100644
--- a/client/decoder/flac_decoder.cpp
+++ b/client/decoder/flac_decoder.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,11 +16,15 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// prototype/interface header file
 #include "flac_decoder.hpp"
+
+// local headers
 #include "common/aixlog.hpp"
 #include "common/endian.hpp"
 #include "common/snap_exception.hpp"
-#include <cmath>
+
+// standard headers
 #include <cstring>
 #include <iostream>
 
diff --git a/client/decoder/flac_decoder.hpp b/client/decoder/flac_decoder.hpp
index 70b67380e..a19a62b00 100644
--- a/client/decoder/flac_decoder.hpp
+++ b/client/decoder/flac_decoder.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,15 +16,18 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef FLAC_DECODER_H
-#define FLAC_DECODER_H
+#pragma once
 
+// local headers
 #include "decoder.hpp"
 
+// 3rd party headers
 #include <FLAC/stream_decoder.h>
-#include <atomic>
+
+// standard headers
 #include <memory>
 
+
 namespace decoder
 {
 
@@ -60,5 +63,3 @@ class FlacDecoder : public Decoder
 };
 
 } // namespace decoder
-
-#endif
diff --git a/client/decoder/null_decoder.cpp b/client/decoder/null_decoder.cpp
index 9fae7fd78..6c722980a 100644
--- a/client/decoder/null_decoder.cpp
+++ b/client/decoder/null_decoder.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2023  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -20,9 +20,6 @@
 #include "null_decoder.hpp"
 
 // local headers
-#include "common/aixlog.hpp"
-#include "common/endian.hpp"
-#include "common/snap_exception.hpp"
 
 // 3rd party headers
 
diff --git a/client/decoder/ogg_decoder.cpp b/client/decoder/ogg_decoder.cpp
index 8540fcbe3..73ca41bb4 100644
--- a/client/decoder/ogg_decoder.cpp
+++ b/client/decoder/ogg_decoder.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2023  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -28,10 +28,8 @@
 // 3rd party headers
 
 // standard headers
-#include <cmath>
 #include <cstdint>
 #include <cstring>
-#include <iostream>
 
 
 
diff --git a/client/decoder/ogg_decoder.hpp b/client/decoder/ogg_decoder.hpp
index b20182fc0..8a4f8c2d9 100644
--- a/client/decoder/ogg_decoder.hpp
+++ b/client/decoder/ogg_decoder.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,9 +16,12 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef OGG_DECODER_H
-#define OGG_DECODER_H
+#pragma once
+
+// local headers
 #include "decoder.hpp"
+
+// 3rd party headers
 #ifdef HAS_TREMOR
 #include <tremor/ivorbiscodec.h>
 #else
@@ -64,5 +67,3 @@ class OggDecoder : public Decoder
 };
 
 } // namespace decoder
-
-#endif
diff --git a/client/decoder/opus_decoder.cpp b/client/decoder/opus_decoder.cpp
index 41303ae0c..facc6f988 100644
--- a/client/decoder/opus_decoder.cpp
+++ b/client/decoder/opus_decoder.cpp
@@ -1,7 +1,7 @@
 /***
     This file is part of snapcast
     Copyright (C) 2015  Hannes Ellinger
-    Copyright (C) 2016-2021  Johannes Pohl
+    Copyright (C) 2016-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -17,10 +17,13 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// prototype/interface header file
 #include "opus_decoder.hpp"
+
+// local headers
 #include "common/aixlog.hpp"
 #include "common/snap_exception.hpp"
-#include "common/str_compat.hpp"
+
 
 namespace decoder
 {
diff --git a/client/decoder/opus_decoder.hpp b/client/decoder/opus_decoder.hpp
index 2152d0935..1e71c8446 100644
--- a/client/decoder/opus_decoder.hpp
+++ b/client/decoder/opus_decoder.hpp
@@ -1,6 +1,7 @@
 /***
         This file is part of snapcast
         Copyright (C) 2015  Hannes Ellinger
+        Copyright (C) 2016-2024  Johannes Pohl
 
         This program is free software: you can redistribute it and/or modify
         it under the terms of the GNU General Public License as published by
@@ -18,9 +19,16 @@
 
 #pragma once
 
+// local headers
 #include "decoder/decoder.hpp"
+
+// 3rd party headers
 #include <opus/opus.h>
 
+// standard headers
+#include <vector>
+
+
 namespace decoder
 {
 
diff --git a/client/decoder/pcm_decoder.cpp b/client/decoder/pcm_decoder.cpp
index 4451a9a4f..e03245a35 100644
--- a/client/decoder/pcm_decoder.cpp
+++ b/client/decoder/pcm_decoder.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,11 +16,14 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// prototype/interface header file
 #include "pcm_decoder.hpp"
-#include "common/aixlog.hpp"
+
+// local headers
 #include "common/endian.hpp"
 #include "common/snap_exception.hpp"
 
+
 namespace decoder
 {
 
diff --git a/client/decoder/pcm_decoder.hpp b/client/decoder/pcm_decoder.hpp
index 5e0b92f2c..b69d6de35 100644
--- a/client/decoder/pcm_decoder.hpp
+++ b/client/decoder/pcm_decoder.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,8 +16,9 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef PCM_DECODER_H
-#define PCM_DECODER_H
+#pragma once
+
+// local headers
 #include "decoder.hpp"
 
 
@@ -33,5 +34,3 @@ class PcmDecoder : public Decoder
 };
 
 } // namespace decoder
-
-#endif
diff --git a/client/double_buffer.hpp b/client/double_buffer.hpp
index dad3dfb56..9163bb215 100644
--- a/client/double_buffer.hpp
+++ b/client/double_buffer.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -22,6 +22,8 @@
 // standard headers
 #include <algorithm>
 #include <array>
+#include <cstddef>
+#include <cstdint>
 #include <deque>
 
 
diff --git a/client/metadata.hpp b/client/metadata.hpp
index ddc1d0f15..cdc18512d 100644
--- a/client/metadata.hpp
+++ b/client/metadata.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,11 +16,15 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef METADATA_H
-#define METADATA_H
+#pragma once
 
+// local headers
 #include "common/json.hpp"
 
+// standard headers
+#include <iostream>
+
+
 // Prefix used in output
 #define METADATA std::string("metadata")
 
@@ -99,5 +103,3 @@ class MetaStderrAdapter : public MetadataAdapter
         return 0;
     }
 };
-
-#endif
diff --git a/client/player/alsa_player.cpp b/client/player/alsa_player.cpp
index 5bf30c765..3c1c89f6f 100644
--- a/client/player/alsa_player.cpp
+++ b/client/player/alsa_player.cpp
@@ -29,6 +29,8 @@
 // 3rd party headers
 
 // standard headers
+#include <chrono>
+
 
 using namespace std::chrono_literals;
 using namespace std;
diff --git a/client/player/alsa_player.hpp b/client/player/alsa_player.hpp
index 77018f754..d189bc29b 100644
--- a/client/player/alsa_player.hpp
+++ b/client/player/alsa_player.hpp
@@ -16,8 +16,7 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef ALSA_PLAYER_HPP
-#define ALSA_PLAYER_HPP
+#pragma once
 
 // local headers
 #include "player.hpp"
@@ -30,6 +29,7 @@
 // standard headers
 #include <chrono>
 #include <optional>
+#include <vector>
 
 
 namespace player
@@ -94,5 +94,3 @@ class AlsaPlayer : public Player
 };
 
 } // namespace player
-
-#endif
\ No newline at end of file
diff --git a/client/player/file_player.cpp b/client/player/file_player.cpp
index e916e8a2d..006a60bb0 100644
--- a/client/player/file_player.cpp
+++ b/client/player/file_player.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2022  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -28,8 +28,7 @@
 // 3rd party headers
 
 // standard headers
-#include <cassert>
-#include <iostream>
+
 
 using namespace std;
 
diff --git a/client/player/oboe_player.cpp b/client/player/oboe_player.cpp
index a92ce0d41..21d944084 100644
--- a/client/player/oboe_player.cpp
+++ b/client/player/oboe_player.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2022  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -21,13 +21,10 @@
 
 // local headers
 #include "common/aixlog.hpp"
-#include "common/snap_exception.hpp"
-#include "common/str_compat.hpp"
 
 // 3rd party headers
 
 // standard headers
-#include <cassert>
 #include <iostream>
 
 
diff --git a/client/player/opensl_player.cpp b/client/player/opensl_player.cpp
index 489953224..1642967ee 100644
--- a/client/player/opensl_player.cpp
+++ b/client/player/opensl_player.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2022  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -27,7 +27,6 @@
 // 3rd party headers
 
 // standard headers
-#include <cassert>
 #include <iostream>
 
 
diff --git a/client/player/player.hpp b/client/player/player.hpp
index 842baea2f..e372402fa 100644
--- a/client/player/player.hpp
+++ b/client/player/player.hpp
@@ -16,12 +16,10 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef PLAYER_HPP
-#define PLAYER_HPP
+#pragma once
 
 // local headers
 #include "client_settings.hpp"
-#include "common/aixlog.hpp"
 #include "common/endian.hpp"
 #include "stream.hpp"
 
@@ -32,9 +30,8 @@
 #include <atomic>
 #include <functional>
 #include <mutex>
-#include <string>
 #include <thread>
-#include <vector>
+
 
 #if !defined(WINDOWS)
 #define SUPPORTS_VOLUME_SCRIPT
@@ -137,5 +134,3 @@ inline bool operator!=(const Player::Volume& lhs, const Player::Volume& rhs)
 }
 
 } // namespace player
-
-#endif
diff --git a/client/player/pulse_player.cpp b/client/player/pulse_player.cpp
index 06f364528..21e9b8b9f 100644
--- a/client/player/pulse_player.cpp
+++ b/client/player/pulse_player.cpp
@@ -30,7 +30,6 @@
 #include <pulse/proplist.h>
 
 // standard headers
-#include <cassert>
 #include <iostream>
 
 
diff --git a/client/player/pulse_player.hpp b/client/player/pulse_player.hpp
index ad2e40315..5836f9e80 100644
--- a/client/player/pulse_player.hpp
+++ b/client/player/pulse_player.hpp
@@ -16,8 +16,7 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef PULSE_PLAYER_HPP
-#define PULSE_PLAYER_HPP
+#pragma once
 
 // local headers
 #include "player.hpp"
@@ -91,5 +90,3 @@ class PulsePlayer : public Player
 };
 
 } // namespace player
-
-#endif
diff --git a/client/player/wasapi_player.cpp b/client/player/wasapi_player.cpp
index 2c950feba..385ef5554 100644
--- a/client/player/wasapi_player.cpp
+++ b/client/player/wasapi_player.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2022  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -26,7 +26,6 @@
 // 3rd party headers
 #include <initguid.h>
 #include <mmdeviceapi.h>
-//#include <functiondiscoverykeys_devpkey.h>
 
 // standard headers
 #include <audioclient.h>
@@ -37,10 +36,7 @@
 #include <mmdeviceapi.h>
 
 #include <cassert>
-#include <chrono>
-#include <codecvt>
-#include <functional>
-#include <locale>
+
 
 using namespace std;
 using namespace std::chrono;
diff --git a/client/snapclient.cpp b/client/snapclient.cpp
index 577009364..f05b328da 100644
--- a/client/snapclient.cpp
+++ b/client/snapclient.cpp
@@ -37,7 +37,6 @@
 #include "common/aixlog.hpp"
 #include "common/snap_exception.hpp"
 #include "common/str_compat.hpp"
-#include "common/utils.hpp"
 #include "common/version.hpp"
 
 // 3rd party headers
@@ -45,7 +44,6 @@
 #include <boost/asio/signal_set.hpp>
 
 // standard headers
-#include <chrono>
 #include <iostream>
 #ifndef WINDOWS
 #include <csignal>
diff --git a/client/stream.cpp b/client/stream.cpp
index c42131d90..6fe5da6b0 100644
--- a/client/stream.cpp
+++ b/client/stream.cpp
@@ -408,7 +408,7 @@ bool Stream::getPlayerChunk(void* outputBuffer, const cs::usec& outputBufferDacT
             auto miniMedian = miniBuffer_.median();
             if ((cs::usec(shortMedian_) > kCorrectionBegin) && (cs::usec(miniMedian) > cs::usec(50)) && (cs::usec(age) > cs::usec(50)))
             {
-                double rate = (shortMedian_ / 100) * 0.00005;
+                double rate = (shortMedian_ / 100.) * 0.00005;
                 rate = 1.0 - std::min(rate, 0.0005);
                 // LOG(INFO, LOG_TAG) << "Rate: " << rate << "\n";
                 // we are late (age > 0), this means we are not playing fast enough
@@ -417,7 +417,7 @@ bool Stream::getPlayerChunk(void* outputBuffer, const cs::usec& outputBufferDacT
             }
             else if ((cs::usec(shortMedian_) < -kCorrectionBegin) && (cs::usec(miniMedian) < -cs::usec(50)) && (cs::usec(age) < -cs::usec(50)))
             {
-                double rate = (-shortMedian_ / 100) * 0.00005;
+                double rate = (-shortMedian_ / 100.) * 0.00005;
                 rate = 1.0 + std::min(rate, 0.0005);
                 // LOG(INFO, LOG_TAG) << "Rate: " << rate << "\n";
                 // we are early (age > 0), this means we are playing too fast
diff --git a/client/stream.hpp b/client/stream.hpp
index 6ab170c76..89f91afd1 100644
--- a/client/stream.hpp
+++ b/client/stream.hpp
@@ -16,28 +16,25 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef STREAM_HPP
-#define STREAM_HPP
+#pragma once
 
 // local headers
-#include "common/message/message.hpp"
 #include "common/message/pcm_chunk.hpp"
-#include "common/queue.h"
+#include "common/queue.hpp"
 #include "common/resampler.hpp"
 #include "common/sample_format.hpp"
 #include "common/utils/logging.hpp"
 #include "double_buffer.hpp"
 
 // 3rd party headers
+#ifdef HAS_SOXR
+#include <soxr.h>
+#endif
 
 // standard headers
 #include <atomic>
-#include <deque>
 #include <memory>
 
-#ifdef HAS_SOXR
-#include <soxr.h>
-#endif
 
 
 /// Time synchronized audio stream
@@ -139,7 +136,3 @@ class Stream
     /// Log "failed to get chunk" only once per second
     utils::logging::TimeConditional time_cond_;
 };
-
-
-
-#endif
diff --git a/client/time_provider.cpp b/client/time_provider.cpp
index 97e2c60fd..d6478c273 100644
--- a/client/time_provider.cpp
+++ b/client/time_provider.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,9 +16,13 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// prototype/interface header file
 #include "time_provider.hpp"
+
+// local headers
 #include "common/aixlog.hpp"
 
+// standard headers
 #include <chrono>
 
 static constexpr auto LOG_TAG = "TimeProvider";
diff --git a/common/daemon.cpp b/common/daemon.cpp
index 89add9690..aa997567c 100644
--- a/common/daemon.cpp
+++ b/common/daemon.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,17 +16,19 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// prototype/interface header file
 #include "daemon.hpp"
 
+// local headers
 #include "common/snap_exception.hpp"
 #include "common/str_compat.hpp"
-#include "common/utils.hpp"
 #include "common/utils/file_utils.hpp"
+
+// standard headers
 #include <cstdlib>
 #include <cstring>
 #include <fcntl.h>
 #include <grp.h>
-#include <iostream>
 #include <pwd.h>
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -102,14 +104,14 @@ void Daemon::daemonize()
     if (user_gid != static_cast<gid_t>(-1) && user_gid != getgid() && setgid(user_gid) == -1)
         throw SnapException("Failed to set group " + cpt::to_string(static_cast<int>(user_gid)));
 
-    //#if defined(FREEBSD) && !defined(MACOS)
-    //#ifdef FREEBSD
+    // #if defined(FREEBSD) && !defined(MACOS)
+    // #ifdef FREEBSD
     /// init supplementary groups
     /// (must be done before we change our uid)
     /// no need to set the new user's supplementary groups if we are already this user
     //	if (!had_group && user_uid != getuid() && initgroups(user_name, user_gid) == -1)
     //		throw SnapException("Failed to set supplementary groups of user \"" + user + "\"");
-    //#endif
+    // #endif
     /// set uid
     if (user_uid != static_cast<uid_t>(-1) && user_uid != getuid() && setuid(user_uid) == -1)
         throw SnapException("Failed to set user " + user_);
diff --git a/common/daemon.hpp b/common/daemon.hpp
index b2e2069ca..b2e52286b 100644
--- a/common/daemon.hpp
+++ b/common/daemon.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,9 +16,10 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef DAEMON_H
-#define DAEMON_H
+#pragma once
 
+
+// standard headers
 #include <string>
 
 
@@ -36,6 +37,3 @@ class Daemon
     std::string group_;
     std::string pidfile_;
 };
-
-
-#endif // DAEMON_H
diff --git a/common/endian.hpp b/common/endian.hpp
index 6b131a986..96d139b49 100644
--- a/common/endian.hpp
+++ b/common/endian.hpp
@@ -1,6 +1,24 @@
-#ifndef ENDIAN_HPP
-#define ENDIAN_HPP
+/***
+    This file is part of snapcast
+    Copyright (C) 2014-2024  Johannes Pohl
 
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#pragma once
+
+// standard headers
 #include <cstdint>
 
 #ifdef IS_BIG_ENDIAN
@@ -43,5 +61,3 @@ inline int64_t swap(const int64_t& val)
     return SWAP_64(val);
 }
 } // namespace endian
-
-#endif
diff --git a/common/error_code.hpp b/common/error_code.hpp
index 946eda697..cbc2744c4 100644
--- a/common/error_code.hpp
+++ b/common/error_code.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,10 +16,9 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef ERROR_CODE_HPP
-#define ERROR_CODE_HPP
-
+#pragma once
 
+// standard headers
 #include <optional>
 #include <string>
 #include <system_error>
@@ -55,7 +54,3 @@ struct ErrorCode : public std::error_code
 
 
 } // namespace snapcast
-
-
-
-#endif
diff --git a/common/message/factory.hpp b/common/message/factory.hpp
index 7c921c031..ac236ed66 100644
--- a/common/message/factory.hpp
+++ b/common/message/factory.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2023  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,23 +16,16 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef MESSAGE_FACTORY_HPP
-#define MESSAGE_FACTORY_HPP
+#pragma once
 
 // local headers
 #include "client_info.hpp"
 #include "codec_header.hpp"
-#include "common/str_compat.hpp"
-#include "common/utils.hpp"
 #include "hello.hpp"
-#include "json_message.hpp"
 #include "pcm_chunk.hpp"
 #include "server_settings.hpp"
 #include "time.hpp"
 
-// standard headers
-#include <string>
-
 
 namespace msg
 {
@@ -91,5 +84,3 @@ static std::unique_ptr<BaseMessage> createMessage(const BaseMessage& base_messag
 
 } // namespace factory
 } // namespace msg
-
-#endif
diff --git a/common/message/message.hpp b/common/message/message.hpp
index d9ca8cd7c..4bb52e437 100644
--- a/common/message/message.hpp
+++ b/common/message/message.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2023  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,8 +16,7 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef MESSAGE_MESSAGE_HPP
-#define MESSAGE_MESSAGE_HPP
+#pragma once
 
 // local headers
 #include "common/endian.hpp"
@@ -32,7 +31,6 @@
 #include <sys/time.h>
 #endif
 #include <memory>
-#include <vector>
 
 /*
 template<typename CharT, typename TraitsT = std::char_traits<CharT> >
@@ -344,5 +342,3 @@ struct BaseMessage
 };
 
 } // namespace msg
-
-#endif
diff --git a/common/message/wire_chunk.hpp b/common/message/wire_chunk.hpp
index a11a26233..979175e91 100644
--- a/common/message/wire_chunk.hpp
+++ b/common/message/wire_chunk.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2022  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,8 +16,7 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef MESSAGE_WIRE_CHUNK_HPP
-#define MESSAGE_WIRE_CHUNK_HPP
+#pragma once
 
 // local headers
 #include "common/time_defs.hpp"
@@ -28,8 +27,6 @@
 #include <cstdlib>
 #include <cstring>
 #include <iostream>
-#include <streambuf>
-#include <vector>
 
 
 namespace msg
@@ -95,6 +92,3 @@ class WireChunk : public BaseMessage
     }
 };
 } // namespace msg
-
-
-#endif
diff --git a/common/queue.h b/common/queue.hpp
similarity index 97%
rename from common/queue.h
rename to common/queue.hpp
index fcb504881..6648aeca0 100644
--- a/common/queue.h
+++ b/common/queue.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,14 +16,14 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef QUEUE_H
-#define QUEUE_H
+#pragma once
 
+// standard headers
 #include <atomic>
 #include <condition_variable>
 #include <deque>
 #include <mutex>
-#include <thread>
+
 
 template <typename T>
 class Queue
@@ -164,6 +164,3 @@ class Queue
     mutable std::mutex mutex_;
     mutable std::condition_variable cond_;
 };
-
-
-#endif
diff --git a/common/resampler.cpp b/common/resampler.cpp
index 929fceae9..1d5d698ac 100644
--- a/common/resampler.cpp
+++ b/common/resampler.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,12 +16,16 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// prototype/interface header file
 #include "resampler.hpp"
+
+// local headers
 #include "common/aixlog.hpp"
-#include "common/snap_exception.hpp"
 
+// standard headers
 #include <cmath>
 
+
 using namespace std;
 
 static constexpr auto LOG_TAG = "Resampler";
diff --git a/common/resampler.hpp b/common/resampler.hpp
index b6b9517e9..3e191024c 100644
--- a/common/resampler.hpp
+++ b/common/resampler.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,17 +16,21 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef RESAMPLER_HPP
-#define RESAMPLER_HPP
+#pragma once
 
+
+// local headers
 #include "common/message/pcm_chunk.hpp"
 #include "common/sample_format.hpp"
-#include <deque>
-#include <vector>
+
+// 3rd party headers
 #ifdef HAS_SOXR
 #include <soxr.h>
 #endif
 
+// standard headers
+#include <vector>
+
 
 class Resampler
 {
@@ -48,5 +52,3 @@ class Resampler
     soxr_t soxr_{nullptr};
 #endif
 };
-
-#endif
diff --git a/common/sample_format.cpp b/common/sample_format.cpp
index 6c6cecb70..6c867852f 100644
--- a/common/sample_format.cpp
+++ b/common/sample_format.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,16 +16,17 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#include <iostream>
-#include <sstream>
-#include <vector>
 
-#include "common/aixlog.hpp"
+// local headers
+#include "sample_format.hpp"
 #include "common/snap_exception.hpp"
 #include "common/str_compat.hpp"
-#include "common/utils.hpp"
 #include "common/utils/string_utils.hpp"
-#include "sample_format.hpp"
+
+// standard headers
+#include <iostream>
+#include <sstream>
+#include <vector>
 
 
 using namespace std;
diff --git a/common/sample_format.hpp b/common/sample_format.hpp
index b68d00a3c..2cc79170d 100644
--- a/common/sample_format.hpp
+++ b/common/sample_format.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,9 +16,9 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef SAMPLE_FORMAT_H
-#define SAMPLE_FORMAT_H
+#pragma once
 
+// standard headers
 #include <cstdint>
 #include <string>
 
@@ -101,6 +101,3 @@ class SampleFormat
     uint16_t bits_;
     uint16_t channels_;
 };
-
-
-#endif
diff --git a/common/snap_exception.hpp b/common/snap_exception.hpp
index f4a9238b7..b40fc97bc 100644
--- a/common/snap_exception.hpp
+++ b/common/snap_exception.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,10 +16,9 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef SNAP_EXCEPTION_HPP
-#define SNAP_EXCEPTION_HPP
+#pragma once
 
-#include <cstring> // std::strlen, std::strcpy
+// standard headers
 #include <exception>
 #include <string>
 
@@ -50,6 +49,3 @@ class SnapException : public std::exception
         return text_.c_str();
     }
 };
-
-
-#endif
diff --git a/common/str_compat.hpp b/common/str_compat.hpp
index da62f10f5..bcdc54d1b 100644
--- a/common/str_compat.hpp
+++ b/common/str_compat.hpp
@@ -1,7 +1,25 @@
-#ifndef COMPAT_H
-#define COMPAT_H
+/***
+    This file is part of snapcast
+    Copyright (C) 2014-2024  Johannes Pohl
 
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
 
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#pragma once
+
+
+// standard headers
 #include <clocale>
 #include <string>
 
@@ -114,6 +132,3 @@ static float strtof(const char* str, char** endptr)
 #endif
 }
 } // namespace cpt
-
-
-#endif
diff --git a/common/time_defs.hpp b/common/time_defs.hpp
index b2a2e1f32..55db73e81 100644
--- a/common/time_defs.hpp
+++ b/common/time_defs.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,9 +16,10 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef TIME_DEFS_H
-#define TIME_DEFS_H
+#pragma once
 
+
+// standard headers
 #include <chrono>
 #include <thread>
 #ifdef MACOS
@@ -34,6 +35,7 @@
 #include <winsock2.h>
 #endif
 
+
 namespace chronos
 {
 using clk =
@@ -159,6 +161,3 @@ inline void usleep(const int32_t& microseconds)
     sleep(usec(microseconds));
 }
 } // namespace chronos
-
-
-#endif
diff --git a/common/utils.hpp b/common/utils.hpp
index b2268ffb6..903f40642 100644
--- a/common/utils.hpp
+++ b/common/utils.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,21 +16,16 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef UTILS_H
-#define UTILS_H
+#pragma once
 
-#include "common/str_compat.hpp"
+
+// local headers
 #include "common/utils/string_utils.hpp"
 
-#include <cctype>
-#include <cerrno>
-// #include <chrono>
+// standard headers
 #include <cstring>
 #include <fstream>
-#include <functional>
 #include <iomanip>
-#include <iterator>
-#include <locale>
 #include <memory>
 #ifndef WINDOWS
 #include <net/if.h>
@@ -43,7 +38,6 @@
 #include <string>
 #include <sys/stat.h>
 #include <sys/types.h>
-#include <vector>
 #if !defined(WINDOWS) && !defined(FREEBSD)
 #include <sys/sysinfo.h>
 #endif
@@ -463,6 +457,3 @@ static std::string getHostId(const std::string& defaultId = "")
     /// The host name should be unique enough in a LAN
     return getHostName();
 }
-
-
-#endif
diff --git a/common/version.hpp b/common/version.hpp
index 13210fd82..eaed3c9a9 100644
--- a/common/version.hpp
+++ b/common/version.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,11 +16,13 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef VERSION_HPP
-#define VERSION_HPP
+#pragma once
 
+
+// standard headers
 #include <string>
 
+
 namespace version
 {
 
@@ -46,5 +48,3 @@ static std::string rev(std::size_t len = 0)
 }
 
 } // namespace version
-
-#endif
diff --git a/server/control_server.hpp b/server/control_server.hpp
index 81b8970b7..ca06b6292 100644
--- a/server/control_server.hpp
+++ b/server/control_server.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2023  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,15 +16,9 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef CONTROL_SERVER_HPP
-#define CONTROL_SERVER_HPP
+#pragma once
 
 // local headers
-#include "common/message/codec_header.hpp"
-#include "common/message/message.hpp"
-#include "common/message/server_settings.hpp"
-#include "common/queue.h"
-#include "common/sample_format.hpp"
 #include "control_session.hpp"
 #include "server_settings.hpp"
 
@@ -35,7 +29,6 @@
 // standard headers
 #include <memory>
 #include <mutex>
-#include <set>
 #include <vector>
 
 
@@ -82,7 +75,3 @@ class ControlServer : public ControlMessageReceiver
     ServerSettings::Http http_settings_;
     ControlMessageReceiver* controlMessageReceiver_;
 };
-
-
-
-#endif
diff --git a/server/control_session.hpp b/server/control_session.hpp
index 59817032b..3fde9b683 100644
--- a/server/control_session.hpp
+++ b/server/control_session.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2023  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,21 +16,15 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef CONTROL_SESSION_HPP
-#define CONTROL_SESSION_HPP
+#pragma once
 
 // local headers
-#include "common/message/message.hpp"
-#include "common/queue.h"
-#include "server_settings.hpp"
 
 // 3rd party headers
 
 // standard headers
-#include <atomic>
-#include <condition_variable>
+#include <functional>
 #include <memory>
-#include <set>
 #include <string>
 
 
@@ -72,7 +66,3 @@ class ControlSession : public std::enable_shared_from_this<ControlSession>
 protected:
     ControlMessageReceiver* message_receiver_;
 };
-
-
-
-#endif
diff --git a/server/control_session_http.hpp b/server/control_session_http.hpp
index 7c33347c6..885232aba 100644
--- a/server/control_session_http.hpp
+++ b/server/control_session_http.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2022  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,11 +16,12 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef CONTROL_SESSION_HTTP_HPP
-#define CONTROL_SESSION_HTTP_HPP
+#pragma once
+
 
 // local headers
 #include "control_session.hpp"
+#include "server_settings.hpp"
 
 // 3rd party headers
 #include <boost/beast/core.hpp>
@@ -77,7 +78,3 @@ class ControlSessionHttp : public ControlSession
     ServerSettings::Http settings_;
     std::deque<std::string> messages_;
 };
-
-
-
-#endif
diff --git a/server/control_session_tcp.cpp b/server/control_session_tcp.cpp
index feb297d94..4311ff066 100644
--- a/server/control_session_tcp.cpp
+++ b/server/control_session_tcp.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2023  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,6 +16,7 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+
 // prototype/interface header file
 #include "control_session_tcp.hpp"
 
@@ -25,7 +26,6 @@
 
 // local headers
 #include "common/aixlog.hpp"
-#include "common/message/pcm_chunk.hpp"
 
 
 using namespace std;
diff --git a/server/server.cpp b/server/server.cpp
index 9cbf5fcc3..6a450fdbc 100644
--- a/server/server.cpp
+++ b/server/server.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2023  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -23,15 +23,16 @@
 #include "common/aixlog.hpp"
 #include "common/message/client_info.hpp"
 #include "common/message/hello.hpp"
+#include "common/message/server_settings.hpp"
 #include "common/message/time.hpp"
 #include "config.hpp"
-#include "stream_session_tcp.hpp"
 
 // 3rd party headers
 
 // standard headers
 #include <iostream>
 
+
 using namespace std;
 using namespace streamreader;
 
diff --git a/server/server.hpp b/server/server.hpp
index cb2c5194e..b7b007cd7 100644
--- a/server/server.hpp
+++ b/server/server.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2023  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,15 +16,12 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef SERVER_HPP
-#define SERVER_HPP
+#pragma once
+
 
 // local headers
-#include "common/message/codec_header.hpp"
 #include "common/message/message.hpp"
-#include "common/message/server_settings.hpp"
-#include "common/queue.h"
-#include "common/sample_format.hpp"
+#include "common/queue.hpp"
 #include "control_server.hpp"
 #include "jsonrpcpp.hpp"
 #include "server_settings.hpp"
@@ -38,10 +35,6 @@
 
 // standard headers
 #include <memory>
-#include <mutex>
-#include <set>
-#include <sstream>
-#include <vector>
 
 
 using namespace streamreader;
@@ -102,7 +95,3 @@ class Server : public StreamMessageReceiver, public ControlMessageReceiver, publ
     std::unique_ptr<StreamServer> streamServer_;
     std::unique_ptr<StreamManager> streamManager_;
 };
-
-
-
-#endif
diff --git a/server/server_settings.hpp b/server/server_settings.hpp
index 61430039f..9cb34ffdb 100644
--- a/server/server_settings.hpp
+++ b/server/server_settings.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,14 +16,16 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef SERVER_SETTINGS_HPP
-#define SERVER_SETTINGS_HPP
+#pragma once
 
-#include <string>
-#include <vector>
 
+// local headers
 #include "image_cache.hpp"
 
+// standard headers
+#include <string>
+#include <vector>
+
 
 struct ServerSettings
 {
@@ -83,5 +85,3 @@ struct ServerSettings
     StreamingClient streamingclient;
     Logging logging;
 };
-
-#endif
diff --git a/server/stream_server.hpp b/server/stream_server.hpp
index c13806ea2..c55637fdd 100644
--- a/server/stream_server.hpp
+++ b/server/stream_server.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2023  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,20 +16,15 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef STREAM_SERVER_HPP
-#define STREAM_SERVER_HPP
+#pragma once
+
 
 // local headers
-#include "common/message/codec_header.hpp"
 #include "common/message/message.hpp"
-#include "common/message/server_settings.hpp"
-#include "common/queue.h"
-#include "common/sample_format.hpp"
+#include "common/queue.hpp"
 #include "control_server.hpp"
-#include "jsonrpcpp.hpp"
 #include "server_settings.hpp"
 #include "stream_session.hpp"
-#include "streamreader/stream_manager.hpp"
 
 // 3rd party headers
 #include <boost/asio/io_context.hpp>
@@ -38,8 +33,6 @@
 // standard headers
 #include <memory>
 #include <mutex>
-#include <set>
-#include <sstream>
 #include <vector>
 
 
@@ -94,7 +87,3 @@ class StreamServer : public StreamMessageReceiver
     Queue<std::shared_ptr<msg::BaseMessage>> messages_;
     StreamMessageReceiver* messageReceiver_;
 };
-
-
-
-#endif
diff --git a/server/stream_session.hpp b/server/stream_session.hpp
index e1529de42..eeb464ac7 100644
--- a/server/stream_session.hpp
+++ b/server/stream_session.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2023  Johannes Pohl
+    Copyright (C) 2014-2024  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,12 +16,11 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef STREAM_SESSION_HPP
-#define STREAM_SESSION_HPP
+#pragma once
+
 
 // local headers
 #include "common/message/message.hpp"
-#include "common/queue.h"
 #include "streamreader/stream_manager.hpp"
 
 // 3rd party headers
@@ -30,12 +29,9 @@
 #include <boost/asio/strand.hpp>
 
 // standard headers
-#include <atomic>
-#include <condition_variable>
 #include <deque>
 #include <memory>
 #include <mutex>
-#include <set>
 #include <sstream>
 #include <string>
 #include <vector>
@@ -166,7 +162,3 @@ class StreamSession : public std::enable_shared_from_this<StreamSession>
     std::deque<shared_const_buffer> messages_;
     mutable std::mutex mutex_;
 };
-
-
-
-#endif