diff --git a/src/base/bittorrent/addtorrentparams.h b/src/base/bittorrent/addtorrentparams.h
index 42a837019..59aa3a42b 100644
--- a/src/base/bittorrent/addtorrentparams.h
+++ b/src/base/bittorrent/addtorrentparams.h
@@ -33,10 +33,11 @@
 #include <QVector>
 
 #include "../tristatebool.h"
-#include "downloadpriority.h"
 
 namespace BitTorrent
 {
+    enum class DownloadPriority;
+
     struct AddTorrentParams
     {
         QString name;
diff --git a/src/base/bittorrent/peerinfo.cpp b/src/base/bittorrent/peerinfo.cpp
index 8e4277e4b..82f8982ff 100644
--- a/src/base/bittorrent/peerinfo.cpp
+++ b/src/base/bittorrent/peerinfo.cpp
@@ -28,6 +28,8 @@
 
 #include "peerinfo.h"
 
+#include <QBitArray>
+
 #include "base/bittorrent/torrenthandle.h"
 #include "base/net/geoipmanager.h"
 #include "base/unicodestrings.h"
diff --git a/src/base/bittorrent/peerinfo.h b/src/base/bittorrent/peerinfo.h
index 6fb3114af..a0741743d 100644
--- a/src/base/bittorrent/peerinfo.h
+++ b/src/base/bittorrent/peerinfo.h
@@ -31,10 +31,11 @@
 
 #include <libtorrent/peer_info.hpp>
 
-#include <QBitArray>
 #include <QCoreApplication>
 #include <QHostAddress>
 
+class QBitArray;
+
 namespace BitTorrent
 {
     class TorrentHandle;
diff --git a/src/base/bittorrent/torrenthandle.cpp b/src/base/bittorrent/torrenthandle.cpp
index f11e5e15c..d807212ea 100644
--- a/src/base/bittorrent/torrenthandle.cpp
+++ b/src/base/bittorrent/torrenthandle.cpp
@@ -59,6 +59,7 @@
 #include "base/profile.h"
 #include "base/tristatebool.h"
 #include "base/utils/fs.h"
+#include "downloadpriority.h"
 #include "peerinfo.h"
 #include "session.h"
 #include "trackerentry.h"
diff --git a/src/base/bittorrent/torrenthandle.h b/src/base/bittorrent/torrenthandle.h
index 4eaf94482..4513d805e 100644
--- a/src/base/bittorrent/torrenthandle.h
+++ b/src/base/bittorrent/torrenthandle.h
@@ -45,7 +45,6 @@
 #include <QVector>
 
 #include "private/speedmonitor.h"
-#include "downloadpriority.h"
 #include "infohash.h"
 #include "torrentinfo.h"
 
@@ -58,6 +57,7 @@ class QUrl;
 
 namespace BitTorrent
 {
+    enum class DownloadPriority;
     class PeerInfo;
     class Session;
     class TrackerEntry;
diff --git a/src/base/http/connection.h b/src/base/http/connection.h
index 4304a9ee5..926d4e44a 100644
--- a/src/base/http/connection.h
+++ b/src/base/http/connection.h
@@ -34,13 +34,12 @@
 #include <QElapsedTimer>
 #include <QObject>
 
-#include "types.h"
-
 class QTcpSocket;
 
 namespace Http
 {
     class IRequestHandler;
+    struct Response;
 
     class Connection : public QObject
     {
diff --git a/src/base/http/irequesthandler.h b/src/base/http/irequesthandler.h
index 0d2cf9a5c..99e6cf574 100644
--- a/src/base/http/irequesthandler.h
+++ b/src/base/http/irequesthandler.h
@@ -29,10 +29,12 @@
 #ifndef HTTP_IREQUESTHANDLER_H
 #define HTTP_IREQUESTHANDLER_H
 
-#include "types.h"
-
 namespace Http
 {
+    struct Environment;
+    struct Request;
+    struct Response;
+
     class IRequestHandler
     {
     public:
diff --git a/src/base/http/responsegenerator.cpp b/src/base/http/responsegenerator.cpp
index 21d9e42c4..90ee498d5 100644
--- a/src/base/http/responsegenerator.cpp
+++ b/src/base/http/responsegenerator.cpp
@@ -31,6 +31,7 @@
 
 #include <QDateTime>
 
+#include "base/http/types.h"
 #include "base/utils/gzip.h"
 
 QByteArray Http::toByteArray(Response response)
diff --git a/src/base/http/responsegenerator.h b/src/base/http/responsegenerator.h
index b7b8e8985..81dcac3a2 100644
--- a/src/base/http/responsegenerator.h
+++ b/src/base/http/responsegenerator.h
@@ -31,10 +31,13 @@
 #ifndef HTTP_RESPONSEGENERATOR_H
 #define HTTP_RESPONSEGENERATOR_H
 
-#include "types.h"
+class QByteArray;
+class QString;
 
 namespace Http
 {
+    struct Response;
+
     QByteArray toByteArray(Response response);
     QString httpDate();
     void compressContent(Response &response);
diff --git a/src/base/preferences.h b/src/base/preferences.h
index 26ed99dbc..9252a0bdb 100644
--- a/src/base/preferences.h
+++ b/src/base/preferences.h
@@ -31,13 +31,13 @@
 #define PREFERENCES_H
 
 #include <QList>
-#include <QStringList>
 
 #include "base/utils/net.h"
 
 class QDateTime;
 class QNetworkCookie;
 class QSize;
+class QStringList;
 class QTime;
 class QVariant;
 
diff --git a/src/base/utils/string.h b/src/base/utils/string.h
index c5cf43c78..5ad1bfbad 100644
--- a/src/base/utils/string.h
+++ b/src/base/utils/string.h
@@ -31,8 +31,8 @@
 #define UTILS_STRING_H
 
 #include <QLatin1String>
-#include <QString>
 
+class QString;
 class TriStateBool;
 
 namespace Utils
diff --git a/src/gui/autoexpandabledialog.h b/src/gui/autoexpandabledialog.h
index 73f2cdbad..692e62587 100644
--- a/src/gui/autoexpandabledialog.h
+++ b/src/gui/autoexpandabledialog.h
@@ -31,7 +31,8 @@
 
 #include <QDialog>
 #include <QLineEdit>
-#include <QString>
+
+class QString;
 
 namespace Ui
 {
diff --git a/src/gui/categoryfiltermodel.h b/src/gui/categoryfiltermodel.h
index 2fd058fb0..f4f550e7a 100644
--- a/src/gui/categoryfiltermodel.h
+++ b/src/gui/categoryfiltermodel.h
@@ -30,15 +30,15 @@
 #define CATEGORYFILTERMODEL_H
 
 #include <QAbstractItemModel>
-#include <QModelIndex>
+
+class QModelIndex;
+class CategoryModelItem;
 
 namespace BitTorrent
 {
     class TorrentHandle;
 }
 
-class CategoryModelItem;
-
 class CategoryFilterModel : public QAbstractItemModel
 {
     Q_OBJECT
diff --git a/src/gui/categoryfilterproxymodel.h b/src/gui/categoryfilterproxymodel.h
index ef6c2e7a5..9e5ee360b 100644
--- a/src/gui/categoryfilterproxymodel.h
+++ b/src/gui/categoryfilterproxymodel.h
@@ -30,7 +30,8 @@
 #define CATEGORYFILTERPROXYMODEL_H
 
 #include <QSortFilterProxyModel>
-#include <QString>
+
+class QString;
 
 class CategoryFilterProxyModel : public QSortFilterProxyModel
 {
diff --git a/src/gui/fspathedit_p.cpp b/src/gui/fspathedit_p.cpp
index 71c7e30a2..4153e1787 100644
--- a/src/gui/fspathedit_p.cpp
+++ b/src/gui/fspathedit_p.cpp
@@ -29,8 +29,11 @@
 #include "fspathedit_p.h"
 
 #include <QCompleter>
+#include <QContextMenuEvent>
 #include <QDir>
 #include <QFileInfo>
+#include <QFileSystemModel>
+#include <QMenu>
 #include <QStringList>
 #include <QStyle>
 
diff --git a/src/gui/fspathedit_p.h b/src/gui/fspathedit_p.h
index 21c553eb0..66029d676 100644
--- a/src/gui/fspathedit_p.h
+++ b/src/gui/fspathedit_p.h
@@ -29,20 +29,19 @@
 #ifndef QBT_GUI_FSPATHEDIT_P_H
 #define QBT_GUI_FSPATHEDIT_P_H
 
-#include <QAction>
 #include <QComboBox>
-#include <QCompleter>
-#include <QContextMenuEvent>
 #include <QFileIconProvider>
-#include <QFileSystemModel>
-#include <QKeyEvent>
 #include <QLineEdit>
-#include <QMenu>
-#include <QStringRef>
 #include <QValidator>
 #include <QVector>
 
+class QAction;
+class QCompleter;
+class QContextMenuEvent;
+class QFileSystemModel;
+class QKeyEvent;
 class QStringList;
+class QStringRef;
 
 namespace Private
 {
diff --git a/src/gui/properties/downloadedpiecesbar.h b/src/gui/properties/downloadedpiecesbar.h
index ee96d45b5..38bb603b9 100644
--- a/src/gui/properties/downloadedpiecesbar.h
+++ b/src/gui/properties/downloadedpiecesbar.h
@@ -31,10 +31,11 @@
 
 #include <QBitArray>
 #include <QVector>
-#include <QWidget>
 
 #include "piecesbar.h"
 
+class QWidget;
+
 class DownloadedPiecesBar : public PiecesBar
 {
     using base = PiecesBar;
diff --git a/src/gui/properties/propertieswidget.cpp b/src/gui/properties/propertieswidget.cpp
index b6e60dd06..07209d963 100644
--- a/src/gui/properties/propertieswidget.cpp
+++ b/src/gui/properties/propertieswidget.cpp
@@ -29,6 +29,7 @@
 #include "propertieswidget.h"
 
 #include <QAction>
+#include <QClipboard>
 #include <QDateTime>
 #include <QDebug>
 #include <QDir>
diff --git a/src/gui/properties/trackerlistwidget.cpp b/src/gui/properties/trackerlistwidget.cpp
index 34d732dae..0caa12ecf 100644
--- a/src/gui/properties/trackerlistwidget.cpp
+++ b/src/gui/properties/trackerlistwidget.cpp
@@ -30,12 +30,14 @@
 
 #include <QAction>
 #include <QApplication>
+#include <QClipboard>
 #include <QColor>
 #include <QDebug>
 #include <QHash>
 #include <QHeaderView>
 #include <QMenu>
 #include <QMessageBox>
+#include <QShortcut>
 #include <QStringList>
 #include <QTableView>
 #include <QTreeWidgetItem>
diff --git a/src/gui/properties/trackerlistwidget.h b/src/gui/properties/trackerlistwidget.h
index 8fcde45eb..7ea25d4fd 100644
--- a/src/gui/properties/trackerlistwidget.h
+++ b/src/gui/properties/trackerlistwidget.h
@@ -29,13 +29,13 @@
 #ifndef TRACKERLIST_H
 #define TRACKERLIST_H
 
-#include <QClipboard>
 #include <QList>
-#include <QShortcut>
 #include <QTreeWidget>
 
 #include "propertieswidget.h"
 
+class QShortcut;
+
 #define NB_STICKY_ITEM 3
 
 namespace BitTorrent
diff --git a/src/gui/rss/rsswidget.cpp b/src/gui/rss/rsswidget.cpp
index 7f2e33f26..2ca6f8d6a 100644
--- a/src/gui/rss/rsswidget.cpp
+++ b/src/gui/rss/rsswidget.cpp
@@ -37,6 +37,7 @@
 #include <QMenu>
 #include <QMessageBox>
 #include <QRegularExpression>
+#include <QShortcut>
 #include <QStandardItemModel>
 #include <QString>
 
diff --git a/src/gui/rss/rsswidget.h b/src/gui/rss/rsswidget.h
index 6bd150eb9..a4e693f0c 100644
--- a/src/gui/rss/rsswidget.h
+++ b/src/gui/rss/rsswidget.h
@@ -32,8 +32,9 @@
 #define RSSWIDGET_H
 
 #include <QPointer>
-#include <QShortcut>
+#include <QWidget>
 
+class QShortcut;
 class ArticleListWidget;
 class FeedListWidget;
 class QListWidgetItem;
diff --git a/src/gui/search/searchsortmodel.cpp b/src/gui/search/searchsortmodel.cpp
index fcc9e0000..e83e9e753 100644
--- a/src/gui/search/searchsortmodel.cpp
+++ b/src/gui/search/searchsortmodel.cpp
@@ -29,6 +29,7 @@
 #include "searchsortmodel.h"
 
 #include "base/global.h"
+#include "base/utils/string.h"
 
 SearchSortModel::SearchSortModel(QObject *parent)
     : base(parent)
diff --git a/src/gui/search/searchsortmodel.h b/src/gui/search/searchsortmodel.h
index 6434b3dcd..50f782c49 100644
--- a/src/gui/search/searchsortmodel.h
+++ b/src/gui/search/searchsortmodel.h
@@ -31,7 +31,6 @@
 
 #include <QSortFilterProxyModel>
 #include <QStringList>
-#include "base/utils/string.h"
 
 class SearchSortModel : public QSortFilterProxyModel
 {
diff --git a/src/gui/tagfiltermodel.h b/src/gui/tagfiltermodel.h
index 19451bf94..1dd8fd38b 100644
--- a/src/gui/tagfiltermodel.h
+++ b/src/gui/tagfiltermodel.h
@@ -30,17 +30,17 @@
 #define TAGFILTERMODEL_H
 
 #include <QAbstractListModel>
-#include <QModelIndex>
 #include <QSet>
 #include <QVector>
 
+class QModelIndex;
+class TagModelItem;
+
 namespace BitTorrent
 {
     class TorrentHandle;
 }
 
-class TagModelItem;
-
 class TagFilterModel : public QAbstractListModel
 {
     Q_OBJECT
diff --git a/src/gui/tagfilterproxymodel.h b/src/gui/tagfilterproxymodel.h
index 6bb83f457..93b75b585 100644
--- a/src/gui/tagfilterproxymodel.h
+++ b/src/gui/tagfilterproxymodel.h
@@ -30,7 +30,8 @@
 #define TAGFILTERPROXYMODEL_H
 
 #include <QSortFilterProxyModel>
-#include <QString>
+
+class QString;
 
 class TagFilterProxyModel : public QSortFilterProxyModel
 {
diff --git a/src/gui/torrentcontentmodel.cpp b/src/gui/torrentcontentmodel.cpp
index bc336e3aa..902ef34bb 100644
--- a/src/gui/torrentcontentmodel.cpp
+++ b/src/gui/torrentcontentmodel.cpp
@@ -49,6 +49,7 @@
 #endif
 
 #include "base/bittorrent/downloadpriority.h"
+#include "base/bittorrent/torrentinfo.h"
 #include "base/global.h"
 #include "base/utils/fs.h"
 #include "base/utils/misc.h"
diff --git a/src/gui/torrentcontentmodel.h b/src/gui/torrentcontentmodel.h
index fda753aad..7d02189d4 100644
--- a/src/gui/torrentcontentmodel.h
+++ b/src/gui/torrentcontentmodel.h
@@ -30,16 +30,20 @@
 #define TORRENTCONTENTMODEL_H
 
 #include <QAbstractItemModel>
-#include <QModelIndex>
-#include <QVariant>
 #include <QVector>
 
-#include "base/bittorrent/torrentinfo.h"
 #include "torrentcontentmodelitem.h"
 
 class QFileIconProvider;
+class QModelIndex;
+class QVariant;
 class TorrentContentModelFile;
 
+namespace BitTorrent
+{
+    class TorrentInfo;
+}
+
 class TorrentContentModel : public QAbstractItemModel
 {
     Q_OBJECT
diff --git a/src/gui/torrentcontentmodelfile.h b/src/gui/torrentcontentmodelfile.h
index ff972c4b5..61d663d82 100644
--- a/src/gui/torrentcontentmodelfile.h
+++ b/src/gui/torrentcontentmodelfile.h
@@ -29,9 +29,13 @@
 #ifndef TORRENTCONTENTMODELFILE_H
 #define TORRENTCONTENTMODELFILE_H
 
-#include "base/bittorrent/downloadpriority.h"
 #include "torrentcontentmodelitem.h"
 
+namespace BitTorrent
+{
+    enum class DownloadPriority;
+}
+
 class TorrentContentModelFile : public TorrentContentModelItem
 {
 public:
diff --git a/src/gui/torrentcontentmodelfolder.h b/src/gui/torrentcontentmodelfolder.h
index 6e41ef269..a8dfcf3b0 100644
--- a/src/gui/torrentcontentmodelfolder.h
+++ b/src/gui/torrentcontentmodelfolder.h
@@ -29,9 +29,13 @@
 #ifndef TORRENTCONTENTMODELFOLDER_H
 #define TORRENTCONTENTMODELFOLDER_H
 
-#include "base/bittorrent/downloadpriority.h"
 #include "torrentcontentmodelitem.h"
 
+namespace BitTorrent
+{
+    enum class DownloadPriority;
+}
+
 class TorrentContentModelFolder : public TorrentContentModelItem
 {
 public:
diff --git a/src/gui/torrentcontentmodelitem.h b/src/gui/torrentcontentmodelitem.h
index 84e55afb8..49d0516a0 100644
--- a/src/gui/torrentcontentmodelitem.h
+++ b/src/gui/torrentcontentmodelitem.h
@@ -30,10 +30,10 @@
 #define TORRENTCONTENTMODELITEM_H
 
 #include <QList>
-#include <QVariant>
 
 #include "base/bittorrent/downloadpriority.h"
 
+class QVariant;
 class TorrentContentModelFolder;
 
 class TorrentContentModelItem
diff --git a/src/webui/api/apicontroller.h b/src/webui/api/apicontroller.h
index 419d6c390..be620832a 100644
--- a/src/webui/api/apicontroller.h
+++ b/src/webui/api/apicontroller.h
@@ -31,9 +31,10 @@
 #include <QMap>
 #include <QObject>
 #include <QSet>
-#include <QString>
 #include <QVariant>
 
+class QString;
+
 struct ISessionManager;
 using StringMap = QMap<QString, QString>;
 using DataMap = QMap<QString, QByteArray>;
diff --git a/src/webui/api/isessionmanager.h b/src/webui/api/isessionmanager.h
index 9d77dcdb1..1917f803d 100644
--- a/src/webui/api/isessionmanager.h
+++ b/src/webui/api/isessionmanager.h
@@ -28,9 +28,10 @@
 
 #pragma once
 
-#include <QString>
 #include <QVariant>
 
+class QString;
+
 struct ISession
 {
     virtual ~ISession() = default;
diff --git a/src/webui/api/searchcontroller.cpp b/src/webui/api/searchcontroller.cpp
index 0c2597aa2..37491b4cd 100644
--- a/src/webui/api/searchcontroller.cpp
+++ b/src/webui/api/searchcontroller.cpp
@@ -28,6 +28,8 @@
 
 #include "searchcontroller.h"
 
+#include <QJsonArray>
+#include <QJsonObject>
 #include <QSharedPointer>
 
 #include "base/global.h"
@@ -37,6 +39,7 @@
 #include "base/utils/random.h"
 #include "base/utils/string.h"
 #include "apierror.h"
+#include "isessionmanager.h"
 
 class SearchPluginManager;
 
diff --git a/src/webui/api/searchcontroller.h b/src/webui/api/searchcontroller.h
index 38cdc40f5..c2accaefc 100644
--- a/src/webui/api/searchcontroller.h
+++ b/src/webui/api/searchcontroller.h
@@ -29,15 +29,15 @@
 #pragma once
 
 #include <QHash>
-#include <QJsonArray>
-#include <QJsonObject>
 #include <QList>
-#include <QString>
 
 #include "base/search/searchpluginmanager.h"
 #include "apicontroller.h"
-#include "isessionmanager.h"
 
+class QJsonArray;
+class QJsonObject;
+class QStringList;
+struct ISession;
 struct SearchResult;
 
 class SearchController : public APIController