diff --git a/src/app/main.cpp b/src/app/main.cpp
index a26c167d1..b17f6ce7a 100644
--- a/src/app/main.cpp
+++ b/src/app/main.cpp
@@ -261,7 +261,7 @@ int main(int argc, char *argv[])
 
         return app->exec(params.paramList());
     }
-    catch (CommandLineParameterError &er) {
+    catch (const CommandLineParameterError &er) {
         displayBadArgMessage(er.messageForUser());
         return EXIT_FAILURE;
     }
diff --git a/src/base/algorithm.h b/src/base/algorithm.h
index 01aa39324..6eb9089b6 100644
--- a/src/base/algorithm.h
+++ b/src/base/algorithm.h
@@ -50,7 +50,7 @@ namespace Algorithm
     // To be used with associative array types, such as QMap, QHash and it's variants
     template <typename T, typename BinaryPredicate
         , typename std::enable_if_t<HasMappedType<T>::value, int> = 0>
-    void removeIf(T &dict, BinaryPredicate p)
+    void removeIf(T &dict, BinaryPredicate &&p)
     {
         auto it = dict.begin();
         while (it != dict.end())
@@ -60,7 +60,7 @@ namespace Algorithm
     // To be used with set types, such as QSet, std::set
     template <typename T, typename UnaryPredicate
         , typename std::enable_if_t<!HasMappedType<T>::value, int> = 0>
-    void removeIf(T &set, UnaryPredicate p)
+    void removeIf(T &set, UnaryPredicate &&p)
     {
         auto it = set.begin();
         while (it != set.end())
diff --git a/src/base/bittorrent/magneturi.cpp b/src/base/bittorrent/magneturi.cpp
index f15ff39d0..cff9bb6cf 100644
--- a/src/base/bittorrent/magneturi.cpp
+++ b/src/base/bittorrent/magneturi.cpp
@@ -34,6 +34,7 @@
 #include <libtorrent/sha1_hash.hpp>
 
 #include <QRegularExpression>
+#include <QUrl>
 
 #include "infohash.h"
 
diff --git a/src/base/bittorrent/magneturi.h b/src/base/bittorrent/magneturi.h
index e2b8757c3..f82dfc8d6 100644
--- a/src/base/bittorrent/magneturi.h
+++ b/src/base/bittorrent/magneturi.h
@@ -29,15 +29,16 @@
 #ifndef BITTORRENT_MAGNETURI_H
 #define BITTORRENT_MAGNETURI_H
 
+#include <libtorrent/add_torrent_params.hpp>
+
 #include <QList>
 #include <QString>
-#include <QUrl>
-
-#include <libtorrent/add_torrent_params.hpp>
 
 #include "infohash.h"
 #include "trackerentry.h"
 
+class QUrl;
+
 namespace BitTorrent
 {
     class MagnetUri
diff --git a/src/base/bittorrent/peerinfo.h b/src/base/bittorrent/peerinfo.h
index 6aae66f75..6fb3114af 100644
--- a/src/base/bittorrent/peerinfo.h
+++ b/src/base/bittorrent/peerinfo.h
@@ -29,12 +29,12 @@
 #ifndef BITTORRENT_PEERINFO_H
 #define BITTORRENT_PEERINFO_H
 
+#include <libtorrent/peer_info.hpp>
+
 #include <QBitArray>
 #include <QCoreApplication>
 #include <QHostAddress>
 
-#include <libtorrent/peer_info.hpp>
-
 namespace BitTorrent
 {
     class TorrentHandle;
diff --git a/src/base/bittorrent/private/bandwidthscheduler.cpp b/src/base/bittorrent/private/bandwidthscheduler.cpp
index 308b3217e..a541a2427 100644
--- a/src/base/bittorrent/private/bandwidthscheduler.cpp
+++ b/src/base/bittorrent/private/bandwidthscheduler.cpp
@@ -33,6 +33,7 @@
 
 #include <QDate>
 #include <QTime>
+#include <QTimer>
 
 #include "base/preferences.h"
 
diff --git a/src/base/bittorrent/private/filterparserthread.cpp b/src/base/bittorrent/private/filterparserthread.cpp
index cf7b19b81..ba275384c 100644
--- a/src/base/bittorrent/private/filterparserthread.cpp
+++ b/src/base/bittorrent/private/filterparserthread.cpp
@@ -245,7 +245,7 @@ int FilterParserThread::parseDATFilterFile()
                 m_filter.add_rule(startAddr, endAddr, lt::ip_filter::blocked);
                 ++ruleCount;
             }
-            catch (std::exception &e) {
+            catch (const std::exception &e) {
                 ++parseErrorCount;
                 addLog(tr("IP filter exception thrown for line %1. Exception is: %2")
                        .arg(nbLine).arg(QString::fromLocal8Bit(e.what())));
@@ -383,7 +383,7 @@ int FilterParserThread::parseP2PFilterFile()
                 m_filter.add_rule(startAddr, endAddr, lt::ip_filter::blocked);
                 ++ruleCount;
             }
-            catch (std::exception &e) {
+            catch (const std::exception &e) {
                 ++parseErrorCount;
                 addLog(tr("IP filter exception thrown for line %1. Exception is: %2")
                        .arg(nbLine).arg(QString::fromLocal8Bit(e.what())));
@@ -468,7 +468,7 @@ int FilterParserThread::parseP2BFilterFile()
                 m_filter.add_rule(first, last, lt::ip_filter::blocked);
                 ++ruleCount;
             }
-            catch (std::exception &) {}
+            catch (const std::exception &) {}
         }
     }
     else if (version == 3) {
@@ -518,7 +518,7 @@ int FilterParserThread::parseP2BFilterFile()
                 m_filter.add_rule(first, last, lt::ip_filter::blocked);
                 ++ruleCount;
             }
-            catch (std::exception &) {}
+            catch (const std::exception &) {}
 
             if (m_abort) return ruleCount;
         }
@@ -577,7 +577,7 @@ void FilterParserThread::run()
     try {
         emit IPFilterParsed(ruleCount);
     }
-    catch (std::exception &) {
+    catch (const std::exception &) {
         emit IPFilterError();
     }
 
diff --git a/src/base/bittorrent/private/filterparserthread.h b/src/base/bittorrent/private/filterparserthread.h
index 0f374bbf5..7b86aa4f6 100644
--- a/src/base/bittorrent/private/filterparserthread.h
+++ b/src/base/bittorrent/private/filterparserthread.h
@@ -29,10 +29,10 @@
 #ifndef FILTERPARSERTHREAD_H
 #define FILTERPARSERTHREAD_H
 
-#include <QThread>
-
 #include <libtorrent/ip_filter.hpp>
 
+#include <QThread>
+
 class QDataStream;
 
 class FilterParserThread : public QThread
diff --git a/src/base/bittorrent/private/portforwarderimpl.cpp b/src/base/bittorrent/private/portforwarderimpl.cpp
index 23d8d6dbd..1a7eb02bf 100644
--- a/src/base/bittorrent/private/portforwarderimpl.cpp
+++ b/src/base/bittorrent/private/portforwarderimpl.cpp
@@ -28,10 +28,10 @@
 
 #include "portforwarderimpl.h"
 
-#include <QDebug>
-
 #include <libtorrent/session.hpp>
 
+#include <QDebug>
+
 #include "base/logger.h"
 #include "base/settingsstorage.h"
 
diff --git a/src/base/bittorrent/private/resumedatasavingmanager.cpp b/src/base/bittorrent/private/resumedatasavingmanager.cpp
index f9dc7b847..4fd93722d 100644
--- a/src/base/bittorrent/private/resumedatasavingmanager.cpp
+++ b/src/base/bittorrent/private/resumedatasavingmanager.cpp
@@ -28,6 +28,7 @@
 
 #include "resumedatasavingmanager.h"
 
+#include <QByteArray>
 #include <QDebug>
 #include <QSaveFile>
 
diff --git a/src/base/bittorrent/private/resumedatasavingmanager.h b/src/base/bittorrent/private/resumedatasavingmanager.h
index 3f27d94a0..ffef21e91 100644
--- a/src/base/bittorrent/private/resumedatasavingmanager.h
+++ b/src/base/bittorrent/private/resumedatasavingmanager.h
@@ -28,10 +28,11 @@
 
 #pragma once
 
-#include <QByteArray>
 #include <QDir>
 #include <QObject>
 
+class QByteArray;
+
 class ResumeDataSavingManager : public QObject
 {
     Q_OBJECT
diff --git a/src/base/bittorrent/session.cpp b/src/base/bittorrent/session.cpp
index e2ea1d689..184c2dbae 100644
--- a/src/base/bittorrent/session.cpp
+++ b/src/base/bittorrent/session.cpp
@@ -1400,7 +1400,7 @@ void Session::configurePeerClasses()
                    , lt::address_v6::from_string("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff")
                    , 1 << lt::session::global_peer_class_id);
     }
-    catch (std::exception &) {}
+    catch (const std::exception &) {}
 #endif // TORRENT_USE_IPV6
     if (ignoreLimitsOnLAN()) {
         // local networks
@@ -1439,7 +1439,7 @@ void Session::configurePeerClasses()
                        , lt::address_v6::from_string("::1")
                        , 1 << lt::session::local_peer_class_id);
         }
-        catch (std::exception &) {}
+        catch (const std::exception &) {}
 #endif // TORRENT_USE_IPV6
     }
     m_nativeSession->set_peer_class_filter(f);
@@ -1870,7 +1870,7 @@ bool Session::addTorrent_impl(CreateTorrentParams params, const MagnetUri &magne
 #endif
                 handle.pause();
             }
-            catch (std::exception &) {}
+            catch (const std::exception &) {}
 
             adjustLimits();
 
@@ -3856,7 +3856,7 @@ void Session::handleAlert(const lt::alert *a)
             break;
         }
     }
-    catch (std::exception &exc) {
+    catch (const std::exception &exc) {
         qWarning() << "Caught exception in " << Q_FUNC_INFO << ": " << QString::fromStdString(exc.what());
     }
 }
@@ -4374,7 +4374,7 @@ namespace
         try {
             handle.queue_position_up();
         }
-        catch (std::exception &exc) {
+        catch (const std::exception &exc) {
             qDebug() << Q_FUNC_INFO << " fails: " << exc.what();
         }
     }
@@ -4384,7 +4384,7 @@ namespace
         try {
             handle.queue_position_down();
         }
-        catch (std::exception &exc) {
+        catch (const std::exception &exc) {
             qDebug() << Q_FUNC_INFO << " fails: " << exc.what();
         }
     }
@@ -4394,7 +4394,7 @@ namespace
         try {
             handle.queue_position_top();
         }
-        catch (std::exception &exc) {
+        catch (const std::exception &exc) {
             qDebug() << Q_FUNC_INFO << " fails: " << exc.what();
         }
     }
@@ -4404,7 +4404,7 @@ namespace
         try {
             handle.queue_position_bottom();
         }
-        catch (std::exception &exc) {
+        catch (const std::exception &exc) {
             qDebug() << Q_FUNC_INFO << " fails: " << exc.what();
         }
     }
diff --git a/src/base/bittorrent/session.h b/src/base/bittorrent/session.h
index d2c91b7e8..65a540414 100644
--- a/src/base/bittorrent/session.h
+++ b/src/base/bittorrent/session.h
@@ -43,7 +43,6 @@
 #include <QSet>
 
 #include "base/settingvalue.h"
-#include "base/tristatebool.h"
 #include "base/types.h"
 #include "addtorrentparams.h"
 #include "cachestatus.h"
diff --git a/src/base/bittorrent/torrenthandle.cpp b/src/base/bittorrent/torrenthandle.cpp
index 09847116c..36be7b90c 100644
--- a/src/base/bittorrent/torrenthandle.cpp
+++ b/src/base/bittorrent/torrenthandle.cpp
@@ -1174,10 +1174,8 @@ QBitArray TorrentHandle::downloadingPieces() const
     std::vector<lt::partial_piece_info> queue;
     m_nativeHandle.get_download_queue(queue);
 
-    std::vector<lt::partial_piece_info>::const_iterator it = queue.begin();
-    std::vector<lt::partial_piece_info>::const_iterator itend = queue.end();
-    for (; it != itend; ++it)
-        result.setBit(it->piece_index);
+    for (const lt::partial_piece_info &info : queue)
+        result.setBit(info.piece_index);
 
     return result;
 }
@@ -1577,8 +1575,7 @@ void TorrentHandle::handleTrackerReplyAlert(const lt::tracker_reply_alert *p)
     const QString trackerUrl(p->tracker_url());
     qDebug("Received a tracker reply from %s (Num_peers = %d)", qUtf8Printable(trackerUrl), p->num_peers);
     // Connection was successful now. Remove possible old errors
-    m_trackerInfos[trackerUrl].lastMessage.clear(); // Reset error/warning message
-    m_trackerInfos[trackerUrl].numPeers = p->num_peers;
+    m_trackerInfos[trackerUrl] = {{}, p->num_peers};
 
     m_session->handleTorrentTrackerReply(this, trackerUrl);
 }
diff --git a/src/base/bittorrent/torrenthandle.h b/src/base/bittorrent/torrenthandle.h
index 725ff24f6..14a218965 100644
--- a/src/base/bittorrent/torrenthandle.h
+++ b/src/base/bittorrent/torrenthandle.h
@@ -94,7 +94,7 @@ namespace BitTorrent
     struct TrackerInfo
     {
         QString lastMessage;
-        quint32 numPeers = 0;
+        int numPeers = 0;
     };
 
     enum class TorrentState
diff --git a/src/base/bittorrent/torrentinfo.h b/src/base/bittorrent/torrentinfo.h
index 207736954..f06f64765 100644
--- a/src/base/bittorrent/torrentinfo.h
+++ b/src/base/bittorrent/torrentinfo.h
@@ -29,7 +29,6 @@
 #ifndef BITTORRENT_TORRENTINFO_H
 #define BITTORRENT_TORRENTINFO_H
 
-#include <libtorrent/fwd.hpp>
 #include <libtorrent/torrent_info.hpp>
 #include <libtorrent/version.hpp>
 
diff --git a/src/base/filesystemwatcher.h b/src/base/filesystemwatcher.h
index ac17d7124..af4c96163 100644
--- a/src/base/filesystemwatcher.h
+++ b/src/base/filesystemwatcher.h
@@ -32,9 +32,11 @@
 #include <QDir>
 #include <QFileSystemWatcher>
 #include <QHash>
-#include <QStringList>
+#include <QList>
 #include <QTimer>
 
+class QStringList;
+
 /*
  * Subclassing QFileSystemWatcher in order to support Network File
  * System watching (NFS, CIFS) on Linux and Mac OS.
diff --git a/src/base/http/requestparser.cpp b/src/base/http/requestparser.cpp
index fa5ded1c8..524c57772 100644
--- a/src/base/http/requestparser.cpp
+++ b/src/base/http/requestparser.cpp
@@ -253,7 +253,7 @@ bool RequestParser::parsePostMessage(const QByteArray &data)
 
         // split data by "dash-boundary"
         const QByteArray dashDelimiter = QByteArray("--") + delimiter + CRLF;
-        QList<QByteArray> multipart = splitToViews(data, dashDelimiter, QString::SkipEmptyParts);
+        QVector<QByteArray> multipart = splitToViews(data, dashDelimiter, QString::SkipEmptyParts);
         if (multipart.isEmpty()) {
             qWarning() << Q_FUNC_INFO << "multipart empty";
             return false;
@@ -275,7 +275,7 @@ bool RequestParser::parsePostMessage(const QByteArray &data)
 
 bool RequestParser::parseFormData(const QByteArray &data)
 {
-    const QList<QByteArray> list = splitToViews(data, EOH, QString::KeepEmptyParts);
+    const QVector<QByteArray> list = splitToViews(data, EOH, QString::KeepEmptyParts);
 
     if (list.size() != 2) {
         qWarning() << Q_FUNC_INFO << "multipart/form-data format error";
diff --git a/src/base/iconprovider.h b/src/base/iconprovider.h
index 3bba13361..b6ea47f8c 100644
--- a/src/base/iconprovider.h
+++ b/src/base/iconprovider.h
@@ -31,7 +31,8 @@
 #define ICONPROVIDER_H
 
 #include <QObject>
-#include <QString>
+
+class QString;
 
 class IconProvider : public QObject
 {
diff --git a/src/base/net/smtp.cpp b/src/base/net/smtp.cpp
index 4cffa215c..1e009069a 100644
--- a/src/base/net/smtp.cpp
+++ b/src/base/net/smtp.cpp
@@ -33,10 +33,12 @@
 #include "smtp.h"
 
 #include <QCryptographicHash>
+#include <QDateTime>
 #include <QDebug>
 #include <QHostInfo>
 #include <QStringList>
 #include <QTextCodec>
+
 #ifndef QT_NO_OPENSSL
 #include <QSslSocket>
 #else
diff --git a/src/base/preferences.cpp b/src/base/preferences.cpp
index a96522f5c..81ac30e1f 100644
--- a/src/base/preferences.cpp
+++ b/src/base/preferences.cpp
@@ -29,9 +29,21 @@
 
 #include "preferences.h"
 
+#ifdef Q_OS_MAC
+#include <CoreServices/CoreServices.h>
+#endif
+#ifdef Q_OS_WIN
+#include <shlobj.h>
+#endif
+
+#include <QDateTime>
 #include <QDir>
 #include <QLocale>
+#include <QNetworkCookie>
 #include <QSettings>
+#include <QSize>
+#include <QTime>
+#include <QVariant>
 
 #ifndef DISABLE_GUI
 #include <QApplication>
@@ -40,14 +52,9 @@
 #endif
 
 #ifdef Q_OS_WIN
-#include <shlobj.h>
 #include <QRegularExpression>
 #endif
 
-#ifdef Q_OS_MAC
-#include <CoreServices/CoreServices.h>
-#endif
-
 #include "algorithm.h"
 #include "global.h"
 #include "settingsstorage.h"
diff --git a/src/base/preferences.h b/src/base/preferences.h
index d8aaab2e2..26ed99dbc 100644
--- a/src/base/preferences.h
+++ b/src/base/preferences.h
@@ -30,16 +30,17 @@
 #ifndef PREFERENCES_H
 #define PREFERENCES_H
 
-#include <QDateTime>
 #include <QList>
-#include <QNetworkCookie>
-#include <QSize>
 #include <QStringList>
-#include <QTime>
-#include <QVariant>
 
 #include "base/utils/net.h"
 
+class QDateTime;
+class QNetworkCookie;
+class QSize;
+class QTime;
+class QVariant;
+
 enum SchedulerDays
 {
     EVERY_DAY,
@@ -74,8 +75,6 @@ namespace DNS
     };
 }
 
-class SettingsStorage;
-
 class Preferences : public QObject
 {
     Q_OBJECT
diff --git a/src/base/private/profile_p.cpp b/src/base/private/profile_p.cpp
index 656beeebf..e5a211cc8 100644
--- a/src/base/private/profile_p.cpp
+++ b/src/base/private/profile_p.cpp
@@ -31,8 +31,6 @@
 
 #include <QCoreApplication>
 
-#include "base/utils/fs.h"
-
 Private::Profile::Profile(const QString &configurationName)
     : m_configurationSuffix {configurationName.isEmpty() ? QString() : QLatin1Char('_') + configurationName}
 {
diff --git a/src/base/profile.h b/src/base/profile.h
index 34b627a10..290248105 100644
--- a/src/base/profile.h
+++ b/src/base/profile.h
@@ -33,8 +33,8 @@
 #include <memory>
 
 #include <QSettings>
-#include <QString>
 
+class QString;
 class Application;
 
 namespace Private
diff --git a/src/base/rss/rss_autodownloader.cpp b/src/base/rss/rss_autodownloader.cpp
index 4a8609b3f..10513ac9d 100644
--- a/src/base/rss/rss_autodownloader.cpp
+++ b/src/base/rss/rss_autodownloader.cpp
@@ -37,6 +37,7 @@
 #include <QSaveFile>
 #include <QThread>
 #include <QTimer>
+#include <QUrl>
 #include <QVariant>
 #include <QVector>
 
diff --git a/src/base/rss/rss_autodownloadrule.h b/src/base/rss/rss_autodownloadrule.h
index 15fd113fb..15e22b735 100644
--- a/src/base/rss/rss_autodownloadrule.h
+++ b/src/base/rss/rss_autodownloadrule.h
@@ -29,10 +29,10 @@
 
 #pragma once
 
-#include <QDateTime>
 #include <QSharedDataPointer>
 #include <QVariant>
 
+class QDateTime;
 class QJsonObject;
 class QRegularExpression;
 class TriStateBool;
diff --git a/src/base/scanfoldersmodel.cpp b/src/base/scanfoldersmodel.cpp
index 119b3eea9..8bee1d533 100644
--- a/src/base/scanfoldersmodel.cpp
+++ b/src/base/scanfoldersmodel.cpp
@@ -341,7 +341,7 @@ void ScanFoldersModel::configure()
 {
     const QVariantHash dirs = Preferences::instance()->getScanDirs();
 
-    for (QVariantHash::const_iterator i = dirs.begin(), e = dirs.end(); i != e; ++i) {
+    for (auto i = dirs.cbegin(); i != dirs.cend(); ++i) {
         if (i.value().type() == QVariant::Int)
             addPath(i.key(), static_cast<PathType>(i.value().toInt()), QString());
         else
diff --git a/src/base/search/searchhandler.h b/src/base/search/searchhandler.h
index fae52d05c..3cf71318a 100644
--- a/src/base/search/searchhandler.h
+++ b/src/base/search/searchhandler.h
@@ -32,6 +32,7 @@
 #include <QByteArray>
 #include <QList>
 #include <QObject>
+#include <QString>
 
 class QProcess;
 class QTimer;
diff --git a/src/base/search/searchpluginmanager.cpp b/src/base/search/searchpluginmanager.cpp
index d751cdf80..12d5280b4 100644
--- a/src/base/search/searchpluginmanager.cpp
+++ b/src/base/search/searchpluginmanager.cpp
@@ -37,7 +37,6 @@
 #include <QDomDocument>
 #include <QDomElement>
 #include <QDomNode>
-#include <QList>
 #include <QPointer>
 #include <QProcess>
 
@@ -494,13 +493,13 @@ void SearchPluginManager::parseVersionInfo(const QByteArray &info)
     QHash<QString, PluginVersion> updateInfo;
     int numCorrectData = 0;
 
-    const QList<QByteArray> lines = Utils::ByteArray::splitToViews(info, "\n", QString::SkipEmptyParts);
+    const QVector<QByteArray> lines = Utils::ByteArray::splitToViews(info, "\n", QString::SkipEmptyParts);
     for (QByteArray line : lines) {
         line = line.trimmed();
         if (line.isEmpty()) continue;
         if (line.startsWith('#')) continue;
 
-        const QList<QByteArray> list = Utils::ByteArray::splitToViews(line, ":", QString::SkipEmptyParts);
+        const QVector<QByteArray> list = Utils::ByteArray::splitToViews(line, ":", QString::SkipEmptyParts);
         if (list.size() != 2) continue;
 
         const QString pluginName = list.first().trimmed();
diff --git a/src/base/settingvalue.h b/src/base/settingvalue.h
index e3ff237c1..64998e2d4 100644
--- a/src/base/settingvalue.h
+++ b/src/base/settingvalue.h
@@ -33,7 +33,6 @@
 
 #include <QMetaEnum>
 #include <QString>
-#include <QVariant>
 
 #include "settingsstorage.h"
 
@@ -51,7 +50,7 @@ public:
     // T proxyFunc(const T &a);
     template <typename ProxyFunc>
     explicit CachedSettingValue(const char *keyName, const T &defaultValue
-                                , ProxyFunc proxyFunc)
+                                , ProxyFunc &&proxyFunc)
         : m_keyName(QLatin1String(keyName))
         , m_value(proxyFunc(loadValue(defaultValue)))
     {
diff --git a/src/base/utils/bytearray.cpp b/src/base/utils/bytearray.cpp
index 9ef543e25..128aa93a3 100644
--- a/src/base/utils/bytearray.cpp
+++ b/src/base/utils/bytearray.cpp
@@ -28,15 +28,17 @@
 
 #include "bytearray.h"
 
-#include <QList>
+#include <QByteArray>
 
-QList<QByteArray> Utils::ByteArray::splitToViews(const QByteArray &in, const QByteArray &sep, const QString::SplitBehavior behavior)
+QVector<QByteArray> Utils::ByteArray::splitToViews(const QByteArray &in, const QByteArray &sep, const QString::SplitBehavior behavior)
 {
     if (sep.isEmpty())
         return {in};
 
-    QList<QByteArray> ret;
-
+    QVector<QByteArray> ret;
+    ret.reserve((behavior == QString::KeepEmptyParts)
+                ? (1 + (in.size() / sep.size()))
+                : (1 + (in.size() / (sep.size() + 1))));
     int head = 0;
     while (head < in.size()) {
         int end = in.indexOf(sep, head);
diff --git a/src/base/utils/bytearray.h b/src/base/utils/bytearray.h
index a9e6e89ea..f0d055ecf 100644
--- a/src/base/utils/bytearray.h
+++ b/src/base/utils/bytearray.h
@@ -28,15 +28,17 @@
 
 #pragma once
 
-#include <QByteArray>
 #include <QString>
+#include <QVector>
+
+class QByteArray;
 
 namespace Utils
 {
     namespace ByteArray
     {
-        // Mimic QString::split(sep, behavior)
-        QList<QByteArray> splitToViews(const QByteArray &in, const QByteArray &sep, const QString::SplitBehavior behavior = QString::KeepEmptyParts);
+        // Mimic QString::splitRef(sep, behavior)
+        QVector<QByteArray> splitToViews(const QByteArray &in, const QByteArray &sep, const QString::SplitBehavior behavior = QString::KeepEmptyParts);
 
         // Mimic QByteArray::mid(pos, len) but instead of returning a full-copy,
         // we only return a partial view
diff --git a/src/base/utils/foreignapps.cpp b/src/base/utils/foreignapps.cpp
index 8047a827d..f32b55e45 100644
--- a/src/base/utils/foreignapps.cpp
+++ b/src/base/utils/foreignapps.cpp
@@ -43,6 +43,7 @@
 #endif
 
 #include "base/logger.h"
+#include "base/utils/bytearray.h"
 
 using namespace Utils::ForeignApps;
 
@@ -61,7 +62,7 @@ namespace
             // Software 'Anaconda' installs its own python interpreter
             // and `python --version` returns a string like this:
             // "Python 3.4.3 :: Anaconda 2.3.0 (64-bit)"
-            const QList<QByteArray> outputSplit = procOutput.split(' ');
+            const QVector<QByteArray> outputSplit = Utils::ByteArray::splitToViews(procOutput, " ", QString::SkipEmptyParts);
             if (outputSplit.size() <= 1)
                 return false;
 
diff --git a/src/base/utils/fs.cpp b/src/base/utils/fs.cpp
index ae9d1d31a..ab29a9a2c 100644
--- a/src/base/utils/fs.cpp
+++ b/src/base/utils/fs.cpp
@@ -34,15 +34,6 @@
 #include <memory>
 #endif
 
-#include <QCoreApplication>
-#include <QDebug>
-#include <QDir>
-#include <QDirIterator>
-#include <QFile>
-#include <QFileInfo>
-#include <QStorageInfo>
-#include <QRegularExpression>
-
 #include <sys/stat.h>
 #include <sys/types.h>
 
@@ -58,6 +49,15 @@
 #include <unistd.h>
 #endif
 
+#include <QCoreApplication>
+#include <QDebug>
+#include <QDir>
+#include <QDirIterator>
+#include <QFile>
+#include <QFileInfo>
+#include <QStorageInfo>
+#include <QRegularExpression>
+
 #include "base/bittorrent/torrenthandle.h"
 #include "base/global.h"
 
diff --git a/src/base/utils/misc.cpp b/src/base/utils/misc.cpp
index ee87c3e1d..39c066f75 100644
--- a/src/base/utils/misc.cpp
+++ b/src/base/utils/misc.cpp
@@ -28,9 +28,6 @@
 
 #include "misc.h"
 
-#include <boost/version.hpp>
-#include <libtorrent/version.hpp>
-
 #ifdef Q_OS_WIN
 #include <windows.h>
 #include <Shlobj.h>
@@ -44,7 +41,9 @@
 #include <CoreServices/CoreServices.h>
 #endif
 
+#include <boost/version.hpp>
 #include <openssl/opensslv.h>
+#include <libtorrent/version.hpp>
 
 #include <QCoreApplication>
 #include <QRegularExpression>
@@ -361,30 +360,6 @@ QString Utils::Misc::getUserIDString()
     return uid;
 }
 
-QStringList Utils::Misc::toStringList(const QList<bool> &l)
-{
-    QStringList ret;
-    for (const bool b : l)
-        ret << (b ? "1" : "0");
-    return ret;
-}
-
-QList<int> Utils::Misc::intListfromStringList(const QStringList &l)
-{
-    QList<int> ret;
-    for (const QString &s : l)
-        ret << s.toInt();
-    return ret;
-}
-
-QList<bool> Utils::Misc::boolListfromStringList(const QStringList &l)
-{
-    QList<bool> ret;
-    for (const QString &s : l)
-        ret << (s == "1");
-    return ret;
-}
-
 QString Utils::Misc::parseHtmlLinks(const QString &rawText)
 {
     QString result = rawText;
diff --git a/src/base/utils/misc.h b/src/base/utils/misc.h
index a8ca900f0..7c9a0e371 100644
--- a/src/base/utils/misc.h
+++ b/src/base/utils/misc.h
@@ -36,9 +36,7 @@
 #include <Windows.h>
 #endif
 
-#include <QString>
-#include <QStringList>
-
+class QString;
 enum class ShutdownDialogAction;
 
 /*  Miscellaneous functions that can be useful */
@@ -87,11 +85,6 @@ namespace Utils
         QString userFriendlyDuration(qlonglong seconds);
         QString getUserIDString();
 
-        // Convert functions
-        QStringList toStringList(const QList<bool> &l);
-        QList<int> intListfromStringList(const QStringList &l);
-        QList<bool> boolListfromStringList(const QStringList &l);
-
 #ifdef Q_OS_WIN
         QString windowsSystemPath();
 
diff --git a/src/base/utils/password.cpp b/src/base/utils/password.cpp
index ec9257ab5..e7bf0cbf6 100644
--- a/src/base/utils/password.cpp
+++ b/src/base/utils/password.cpp
@@ -33,7 +33,6 @@
 #include <openssl/evp.h>
 
 #include <QByteArray>
-#include <QList>
 #include <QString>
 
 #include "bytearray.h"
@@ -99,7 +98,7 @@ bool Utils::Password::PBKDF2::verify(const QByteArray &secret, const QString &pa
 
 bool Utils::Password::PBKDF2::verify(const QByteArray &secret, const QByteArray &password)
 {
-    const QList<QByteArray> list = ByteArray::splitToViews(secret, ":", QString::SkipEmptyParts);
+    const QVector<QByteArray> list = ByteArray::splitToViews(secret, ":", QString::SkipEmptyParts);
     if (list.size() != 2)
         return false;
 
diff --git a/src/base/utils/random.cpp b/src/base/utils/random.cpp
index fde12462e..ef46fe860 100644
--- a/src/base/utils/random.cpp
+++ b/src/base/utils/random.cpp
@@ -43,6 +43,8 @@
 #include <cstdio>
 #endif
 
+#include <QString>
+
 #include "misc.h"
 
 namespace
diff --git a/src/gui/optionsdialog.cpp b/src/gui/optionsdialog.cpp
index 14a7d34b7..5368ee190 100644
--- a/src/gui/optionsdialog.cpp
+++ b/src/gui/optionsdialog.cpp
@@ -29,6 +29,7 @@
 #include "optionsdialog.h"
 
 #include <cstdlib>
+#include <limits>
 
 #include <QApplication>
 #include <QCloseEvent>
@@ -62,8 +63,8 @@
 #include "advancedsettings.h"
 #include "app/application.h"
 #include "banlistoptionsdialog.h"
-#include "ipsubnetwhitelistoptionsdialog.h"
 #include "guiiconprovider.h"
+#include "ipsubnetwhitelistoptionsdialog.h"
 #include "rss/automatedrssdownloader.h"
 #include "scanfoldersdelegate.h"
 #include "ui_optionsdialog.h"
@@ -297,7 +298,7 @@ OptionsDialog::OptionsDialog(QWidget *parent)
         .arg(tr("Supported parameters (case sensitive):")
             , tr("%N: Torrent name")
             , tr("%L: Category")
-            , tr("%G: Tags (seperated by comma)")
+            , tr("%G: Tags (separated by comma)")
             , tr("%F: Content path (same as root path for multifile torrent)")
             , tr("%R: Root path (first torrent subdirectory path)")
             , tr("%D: Save path")
diff --git a/src/gui/optionsdialog.h b/src/gui/optionsdialog.h
index 4e3a2d841..1565fdd19 100644
--- a/src/gui/optionsdialog.h
+++ b/src/gui/optionsdialog.h
@@ -29,7 +29,6 @@
 #ifndef OPTIONSDIALOG_H
 #define OPTIONSDIALOG_H
 
-#include <QButtonGroup>
 #include <QDialog>
 
 class QAbstractButton;
diff --git a/src/gui/properties/propertieswidget.cpp b/src/gui/properties/propertieswidget.cpp
index eb10e0d0c..b6e60dd06 100644
--- a/src/gui/properties/propertieswidget.cpp
+++ b/src/gui/properties/propertieswidget.cpp
@@ -29,12 +29,14 @@
 #include "propertieswidget.h"
 
 #include <QAction>
+#include <QDateTime>
 #include <QDebug>
 #include <QDir>
 #include <QHeaderView>
 #include <QListWidgetItem>
 #include <QMenu>
 #include <QSplitter>
+#include <QShortcut>
 #include <QStackedWidget>
 #include <QThread>
 #include <QUrl>
diff --git a/src/gui/properties/propertieswidget.h b/src/gui/properties/propertieswidget.h
index de8b22d2d..c0c5750d3 100644
--- a/src/gui/properties/propertieswidget.h
+++ b/src/gui/properties/propertieswidget.h
@@ -29,14 +29,13 @@
 #ifndef PROPERTIESWIDGET_H
 #define PROPERTIESWIDGET_H
 
-#include <QShortcut>
+#include <QList>
 #include <QWidget>
 
 #include "base/bittorrent/torrenthandle.h"
 
-class QAction;
 class QPushButton;
-class QTimer;
+class QShortcut;
 class QTreeView;
 
 class DownloadedPiecesBar;
@@ -45,8 +44,6 @@ class PeerListWidget;
 class PieceAvailabilityBar;
 class PropListDelegate;
 class PropTabBar;
-class SpeedWidget;
-class torrent_file;
 class TorrentContentFilterModel;
 class TrackerListWidget;
 
diff --git a/src/gui/properties/speedwidget.cpp b/src/gui/properties/speedwidget.cpp
index 0ab151413..b3a1d3b3a 100644
--- a/src/gui/properties/speedwidget.cpp
+++ b/src/gui/properties/speedwidget.cpp
@@ -28,13 +28,12 @@
 
 #include "speedwidget.h"
 
-#include <QVBoxLayout>
+#include <QDateTime>
 #include <QHBoxLayout>
 #include <QLabel>
 #include <QMenu>
 #include <QTimer>
-
-#include <libtorrent/session_status.hpp>
+#include <QVBoxLayout>
 
 #include "base/bittorrent/session.h"
 #include "base/bittorrent/sessionstatus.h"
diff --git a/src/gui/properties/speedwidget.h b/src/gui/properties/speedwidget.h
index 148e40f55..79979b2a0 100644
--- a/src/gui/properties/speedwidget.h
+++ b/src/gui/properties/speedwidget.h
@@ -34,10 +34,10 @@
 
 #include "speedplotview.h"
 
-class QVBoxLayout;
 class QHBoxLayout;
 class QLabel;
 class QMenu;
+class QVBoxLayout;
 class PropertiesWidget;
 
 class ComboBoxMenuButton : public QComboBox
diff --git a/src/gui/torrentcontenttreeview.cpp b/src/gui/torrentcontenttreeview.cpp
index 3d9149508..712964a95 100644
--- a/src/gui/torrentcontenttreeview.cpp
+++ b/src/gui/torrentcontenttreeview.cpp
@@ -69,9 +69,8 @@ void TorrentContentTreeView::keyPressEvent(QKeyEvent *event)
 
     const QModelIndexList selection = selectionModel()->selectedRows(TorrentContentModelItem::COL_NAME);
 
-    for (QModelIndexList::const_iterator i = selection.begin(); i != selection.end(); ++i) {
-        QModelIndex index = *i;
-        Q_ASSERT(i->column() == TorrentContentModelItem::COL_NAME);
+    for (const QModelIndex &index : selection) {
+        Q_ASSERT(index.column() == TorrentContentModelItem::COL_NAME);
         model()->setData(index, state, Qt::CheckStateRole);
     }
 }
diff --git a/src/gui/transferlistdelegate.cpp b/src/gui/transferlistdelegate.cpp
index d64d74e35..7a314310f 100644
--- a/src/gui/transferlistdelegate.cpp
+++ b/src/gui/transferlistdelegate.cpp
@@ -29,6 +29,7 @@
 #include "transferlistdelegate.h"
 
 #include <QApplication>
+#include <QDateTime>
 #include <QModelIndex>
 #include <QPainter>
 #include <QStyleOptionViewItem>
@@ -37,7 +38,6 @@
 #include <QProxyStyle>
 #endif
 
-#include "base/bittorrent/session.h"
 #include "base/bittorrent/torrenthandle.h"
 #include "base/preferences.h"
 #include "base/types.h"
diff --git a/src/webui/api/appcontroller.cpp b/src/webui/api/appcontroller.cpp
index d62942a30..57ca4aa46 100644
--- a/src/webui/api/appcontroller.cpp
+++ b/src/webui/api/appcontroller.cpp
@@ -112,7 +112,7 @@ void AppController::preferencesAction()
     // Automatically add torrents from
     const QVariantHash dirs = pref->getScanDirs();
     QVariantMap nativeDirs;
-    for (QVariantHash::const_iterator i = dirs.cbegin(), e = dirs.cend(); i != e; ++i) {
+    for (auto i = dirs.cbegin(); i != dirs.cend(); ++i) {
         if (i.value().type() == QVariant::Int)
             nativeDirs.insert(Utils::Fs::toNativePath(i.key()), i.value().toInt());
         else
@@ -299,7 +299,7 @@ void AppController::setPreferencesAction()
         QVariantHash oldScanDirs = pref->getScanDirs();
         QVariantHash scanDirs;
         ScanFoldersModel *model = ScanFoldersModel::instance();
-        for (QVariantMap::const_iterator i = nativeDirs.cbegin(), e = nativeDirs.cend(); i != e; ++i) {
+        for (auto i = nativeDirs.cbegin(); i != nativeDirs.cend(); ++i) {
             QString folder = Utils::Fs::fromNativePath(i.key());
             int downloadType;
             QString downloadPath;
diff --git a/src/webui/api/authcontroller.cpp b/src/webui/api/authcontroller.cpp
index 5798f77ec..1a34f163c 100644
--- a/src/webui/api/authcontroller.cpp
+++ b/src/webui/api/authcontroller.cpp
@@ -28,6 +28,9 @@
 
 #include "authcontroller.h"
 
+#include <QDateTime>
+#include <QString>
+
 #include "base/logger.h"
 #include "base/preferences.h"
 #include "base/utils/password.h"
diff --git a/src/webui/api/authcontroller.h b/src/webui/api/authcontroller.h
index 287aee3da..0dd896473 100644
--- a/src/webui/api/authcontroller.h
+++ b/src/webui/api/authcontroller.h
@@ -29,10 +29,11 @@
 #pragma once
 
 #include <QHash>
-#include <QString>
 
 #include "apicontroller.h"
 
+class QString;
+
 class AuthController : public APIController
 {
     Q_OBJECT
diff --git a/src/webui/webapplication.cpp b/src/webui/webapplication.cpp
index c0b15b001..07bbb68ec 100644
--- a/src/webui/webapplication.cpp
+++ b/src/webui/webapplication.cpp
@@ -29,10 +29,6 @@
 #include "webapplication.h"
 
 #include <algorithm>
-#include <functional>
-#include <queue>
-#include <stdexcept>
-#include <vector>
 
 #include <QDateTime>
 #include <QDebug>
@@ -41,13 +37,13 @@
 #include <QJsonDocument>
 #include <QMimeDatabase>
 #include <QMimeType>
+#include <QNetworkCookie>
 #include <QRegExp>
 #include <QUrl>
 
 #include "base/algorithm.h"
 #include "base/global.h"
 #include "base/http/httperror.h"
-#include "base/iconprovider.h"
 #include "base/logger.h"
 #include "base/preferences.h"
 #include "base/utils/bytearray.h"
diff --git a/src/webui/www/private/preferences_content.html b/src/webui/www/private/preferences_content.html
index 068413703..69b380061 100644
--- a/src/webui/www/private/preferences_content.html
+++ b/src/webui/www/private/preferences_content.html
@@ -214,7 +214,7 @@
             <ul>
                 <li>QBT_TR(%N: Torrent name)QBT_TR[CONTEXT=OptionsDialog]</li>
                 <li>QBT_TR(%L: Category)QBT_TR[CONTEXT=OptionsDialog]</li>
-                <li>QBT_TR(%G: Tags (seperated by comma))QBT_TR[CONTEXT=OptionsDialog]</li>
+                <li>QBT_TR(%G: Tags (separated by comma))QBT_TR[CONTEXT=OptionsDialog]</li>
                 <li>QBT_TR(%F: Content path (same as root path for multifile torrent))QBT_TR[CONTEXT=OptionsDialog]</li>
                 <li>QBT_TR(%R: Root path (first torrent subdirectory path))QBT_TR[CONTEXT=OptionsDialog]</li>
                 <li>QBT_TR(%D: Save path)QBT_TR[CONTEXT=OptionsDialog]</li>