diff --git a/src/qt/addressbookpage.cpp b/src/qt/addressbookpage.cpp
index 26bdf60d4a..726dafccb0 100644
--- a/src/qt/addressbookpage.cpp
+++ b/src/qt/addressbookpage.cpp
@@ -59,7 +59,7 @@ class AddressBookSortFilterProxyModel final : public QSortFilterProxyModel
 AddressBookPage::AddressBookPage(const PlatformStyle *platformStyle, Mode _mode, Tabs _tab, QWidget *parent) :
     QDialog(parent),
     ui(new Ui::AddressBookPage),
-    model(0),
+    model(nullptr),
     mode(_mode),
     tab(_tab)
 {
diff --git a/src/qt/addressbookpage.h b/src/qt/addressbookpage.h
index 32ab2dfeb5..6394d26801 100644
--- a/src/qt/addressbookpage.h
+++ b/src/qt/addressbookpage.h
@@ -38,7 +38,7 @@ class AddressBookPage : public QDialog
         ForEditing  /**< Open address book for editing */
     };
 
-    explicit AddressBookPage(const PlatformStyle *platformStyle, Mode mode, Tabs tab, QWidget *parent = 0);
+    explicit AddressBookPage(const PlatformStyle *platformStyle, Mode mode, Tabs tab, QWidget *parent = nullptr);
     ~AddressBookPage();
 
     void setModel(AddressTableModel *model);
diff --git a/src/qt/addresstablemodel.cpp b/src/qt/addresstablemodel.cpp
index 2f88e15d21..289d83e3d5 100644
--- a/src/qt/addresstablemodel.cpp
+++ b/src/qt/addresstablemodel.cpp
@@ -153,7 +153,7 @@ class AddressTablePriv
         }
         else
         {
-            return 0;
+            return nullptr;
         }
     }
 };
diff --git a/src/qt/addresstablemodel.h b/src/qt/addresstablemodel.h
index 41bed4e290..035f3e0571 100644
--- a/src/qt/addresstablemodel.h
+++ b/src/qt/addresstablemodel.h
@@ -25,7 +25,7 @@ class AddressTableModel : public QAbstractTableModel
     Q_OBJECT
 
 public:
-    explicit AddressTableModel(WalletModel *parent = 0);
+    explicit AddressTableModel(WalletModel *parent = nullptr);
     ~AddressTableModel();
 
     enum ColumnIndex {
diff --git a/src/qt/askpassphrasedialog.cpp b/src/qt/askpassphrasedialog.cpp
index 821c23c467..a89a15bc9d 100644
--- a/src/qt/askpassphrasedialog.cpp
+++ b/src/qt/askpassphrasedialog.cpp
@@ -22,7 +22,7 @@ AskPassphraseDialog::AskPassphraseDialog(Mode _mode, QWidget *parent) :
     QDialog(parent),
     ui(new Ui::AskPassphraseDialog),
     mode(_mode),
-    model(0),
+    model(nullptr),
     fCapsLock(false)
 {
     ui->setupUi(this);
diff --git a/src/qt/bantablemodel.cpp b/src/qt/bantablemodel.cpp
index 713db595d5..92cfbee074 100644
--- a/src/qt/bantablemodel.cpp
+++ b/src/qt/bantablemodel.cpp
@@ -76,7 +76,7 @@ class BanTablePriv
         if (idx >= 0 && idx < cachedBanlist.size())
             return &cachedBanlist[idx];
 
-        return 0;
+        return nullptr;
     }
 };
 
diff --git a/src/qt/bantablemodel.h b/src/qt/bantablemodel.h
index b8505b599f..9dec5fa6a9 100644
--- a/src/qt/bantablemodel.h
+++ b/src/qt/bantablemodel.h
@@ -45,7 +45,7 @@ class BanTableModel : public QAbstractTableModel
     Q_OBJECT
 
 public:
-    explicit BanTableModel(interfaces::Node& node, ClientModel *parent = 0);
+    explicit BanTableModel(interfaces::Node& node, ClientModel *parent = nullptr);
     ~BanTableModel();
     void startAutoRefresh();
     void stopAutoRefresh();
diff --git a/src/qt/bitcoin.cpp b/src/qt/bitcoin.cpp
index 6e08dae3c4..e16f8eb3c0 100644
--- a/src/qt/bitcoin.cpp
+++ b/src/qt/bitcoin.cpp
@@ -178,18 +178,18 @@ void BitcoinCore::shutdown()
 
 BitcoinApplication::BitcoinApplication(interfaces::Node& node, int &argc, char **argv):
     QApplication(argc, argv),
-    coreThread(0),
+    coreThread(nullptr),
     m_node(node),
-    optionsModel(0),
-    clientModel(0),
-    window(0),
-    pollShutdownTimer(0),
+    optionsModel(nullptr),
+    clientModel(nullptr),
+    window(nullptr),
+    pollShutdownTimer(nullptr),
 #ifdef ENABLE_WALLET
-    paymentServer(0),
+    paymentServer(nullptr),
     m_wallet_models(),
 #endif
     returnValue(0),
-    platformStyle(0)
+    platformStyle(nullptr)
 {
     setQuitOnLastWindowClosed(false);
 }
@@ -218,15 +218,15 @@ BitcoinApplication::~BitcoinApplication()
     }
 
     delete window;
-    window = 0;
+    window = nullptr;
 #ifdef ENABLE_WALLET
     delete paymentServer;
-    paymentServer = 0;
+    paymentServer = nullptr;
 #endif
     delete optionsModel;
-    optionsModel = 0;
+    optionsModel = nullptr;
     delete platformStyle;
-    platformStyle = 0;
+    platformStyle = nullptr;
 }
 
 #ifdef ENABLE_WALLET
@@ -312,7 +312,7 @@ void BitcoinApplication::requestShutdown()
     qDebug() << __func__ << ": Requesting shutdown";
     startThread();
     window->hide();
-    window->setClientModel(0);
+    window->setClientModel(nullptr);
     pollShutdownTimer->stop();
 
 #ifdef ENABLE_WALLET
@@ -323,7 +323,7 @@ void BitcoinApplication::requestShutdown()
     m_wallet_models.clear();
 #endif
     delete clientModel;
-    clientModel = 0;
+    clientModel = nullptr;
 
     m_node.startShutdown();
 
diff --git a/src/qt/bitcoinamountfield.cpp b/src/qt/bitcoinamountfield.cpp
index 558fcf50ba..121ab2807b 100644
--- a/src/qt/bitcoinamountfield.cpp
+++ b/src/qt/bitcoinamountfield.cpp
@@ -60,7 +60,7 @@ class AmountSpinBox: public QAbstractSpinBox
         }
     }
 
-    CAmount value(bool *valid_out=0) const
+    CAmount value(bool *valid_out=nullptr) const
     {
         return parse(text(), valid_out);
     }
@@ -159,7 +159,7 @@ class AmountSpinBox: public QAbstractSpinBox
      * return validity.
      * @note Must return 0 if !valid.
      */
-    CAmount parse(const QString &text, bool *valid_out=0) const
+    CAmount parse(const QString &text, bool *valid_out=nullptr) const
     {
         CAmount val = 0;
         bool valid = BitcoinUnits::parse(currentUnit, text, &val);
diff --git a/src/qt/bitcoinamountfield.h b/src/qt/bitcoinamountfield.h
index 650481e30d..2db6b65f2c 100644
--- a/src/qt/bitcoinamountfield.h
+++ b/src/qt/bitcoinamountfield.h
@@ -26,9 +26,9 @@ class BitcoinAmountField: public QWidget
     Q_PROPERTY(qint64 value READ value WRITE setValue NOTIFY valueChanged USER true)
 
 public:
-    explicit BitcoinAmountField(QWidget *parent = 0);
+    explicit BitcoinAmountField(QWidget *parent = nullptr);
 
-    CAmount value(bool *value=0) const;
+    CAmount value(bool *value=nullptr) const;
     void setValue(const CAmount& value);
 
     /** If allow empty is set to false the field will be set to the minimum allowed value if left empty. **/
diff --git a/src/qt/bitcoingui.cpp b/src/qt/bitcoingui.cpp
index 155f8efe7f..77130c8c63 100644
--- a/src/qt/bitcoingui.cpp
+++ b/src/qt/bitcoingui.cpp
@@ -95,7 +95,7 @@ BitcoinGUI::BitcoinGUI(interfaces::Node& node, const PlatformStyle *_platformSty
     setWindowIcon(networkStyle->getTrayAndWindowIcon());
     setWindowTitle(windowTitle);
 
-    rpcConsole = new RPCConsole(node, _platformStyle, 0);
+    rpcConsole = new RPCConsole(node, _platformStyle, nullptr);
     helpMessageDialog = new HelpMessageDialog(node, this, false);
 #ifdef ENABLE_WALLET
     if(enableWallet)
@@ -1196,7 +1196,7 @@ void BitcoinGUI::updateProxyIcon()
     bool proxy_enabled = clientModel->getProxyInfo(ip_port);
 
     if (proxy_enabled) {
-        if (labelProxyIcon->pixmap() == 0) {
+        if (labelProxyIcon->pixmap() == nullptr) {
             QString ip_port_q = QString::fromStdString(ip_port);
             labelProxyIcon->setPixmap(platformStyle->SingleColorIcon(":/icons/proxy").pixmap(STATUSBAR_ICONSIZE, STATUSBAR_ICONSIZE));
             labelProxyIcon->setToolTip(tr("Proxy is <b>enabled</b>: %1").arg(ip_port_q));
@@ -1242,7 +1242,7 @@ void BitcoinGUI::showProgress(const QString &title, int nProgress)
         progressDialog = new QProgressDialog(title, "", 0, 100);
         progressDialog->setWindowModality(Qt::ApplicationModal);
         progressDialog->setMinimumDuration(0);
-        progressDialog->setCancelButton(0);
+        progressDialog->setCancelButton(nullptr);
         progressDialog->setAutoClose(false);
         progressDialog->setValue(0);
     }
@@ -1304,8 +1304,8 @@ void BitcoinGUI::unsubscribeFromCoreSignals()
 }
 
 UnitDisplayStatusBarControl::UnitDisplayStatusBarControl(const PlatformStyle *platformStyle) :
-    optionsModel(0),
-    menu(0)
+    optionsModel(nullptr),
+    menu(nullptr)
 {
     createContextMenu();
     setToolTip(tr("Unit to show amounts in. Click to select another unit."));
diff --git a/src/qt/bitcoingui.h b/src/qt/bitcoingui.h
index 9ca9e4c926..48e96d6169 100644
--- a/src/qt/bitcoingui.h
+++ b/src/qt/bitcoingui.h
@@ -67,7 +67,7 @@ class BitcoinGUI : public QMainWindow
 public:
     static const std::string DEFAULT_UIPLATFORM;
 
-    explicit BitcoinGUI(interfaces::Node& node, const PlatformStyle *platformStyle, const NetworkStyle *networkStyle, QWidget *parent = 0);
+    explicit BitcoinGUI(interfaces::Node& node, const PlatformStyle *platformStyle, const NetworkStyle *networkStyle, QWidget *parent = nullptr);
     ~BitcoinGUI();
 
     /** Set the client model.
diff --git a/src/qt/clientmodel.cpp b/src/qt/clientmodel.cpp
index 217326f818..30d9e977b8 100644
--- a/src/qt/clientmodel.cpp
+++ b/src/qt/clientmodel.cpp
@@ -35,9 +35,9 @@ ClientModel::ClientModel(interfaces::Node& node, OptionsModel *_optionsModel, QO
     QObject(parent),
     m_node(node),
     optionsModel(_optionsModel),
-    peerTableModel(0),
-    banTableModel(0),
-    pollTimer(0)
+    peerTableModel(nullptr),
+    banTableModel(nullptr),
+    pollTimer(nullptr)
 {
     cachedBestHeaderHeight = -1;
     cachedBestHeaderTime = -1;
diff --git a/src/qt/clientmodel.h b/src/qt/clientmodel.h
index 79e7074cca..95f4521f06 100644
--- a/src/qt/clientmodel.h
+++ b/src/qt/clientmodel.h
@@ -46,7 +46,7 @@ class ClientModel : public QObject
     Q_OBJECT
 
 public:
-    explicit ClientModel(interfaces::Node& node, OptionsModel *optionsModel, QObject *parent = 0);
+    explicit ClientModel(interfaces::Node& node, OptionsModel *optionsModel, QObject *parent = nullptr);
     ~ClientModel();
 
     interfaces::Node& node() const { return m_node; }
diff --git a/src/qt/coincontroldialog.cpp b/src/qt/coincontroldialog.cpp
index 77f8bcf901..0d9f1adcd2 100644
--- a/src/qt/coincontroldialog.cpp
+++ b/src/qt/coincontroldialog.cpp
@@ -49,7 +49,7 @@ bool CCoinControlWidgetItem::operator<(const QTreeWidgetItem &other) const {
 CoinControlDialog::CoinControlDialog(const PlatformStyle *_platformStyle, QWidget *parent) :
     QDialog(parent),
     ui(new Ui::CoinControlDialog),
-    model(0),
+    model(nullptr),
     platformStyle(_platformStyle)
 {
     ui->setupUi(this);
diff --git a/src/qt/coincontroldialog.h b/src/qt/coincontroldialog.h
index 8f15ae4b20..efc06a7656 100644
--- a/src/qt/coincontroldialog.h
+++ b/src/qt/coincontroldialog.h
@@ -43,7 +43,7 @@ class CoinControlDialog : public QDialog
     Q_OBJECT
 
 public:
-    explicit CoinControlDialog(const PlatformStyle *platformStyle, QWidget *parent = 0);
+    explicit CoinControlDialog(const PlatformStyle *platformStyle, QWidget *parent = nullptr);
     ~CoinControlDialog();
 
     void setModel(WalletModel *model);
diff --git a/src/qt/coincontroltreewidget.h b/src/qt/coincontroltreewidget.h
index 62645fcdb0..88fc8b704f 100644
--- a/src/qt/coincontroltreewidget.h
+++ b/src/qt/coincontroltreewidget.h
@@ -13,7 +13,7 @@ class CoinControlTreeWidget : public QTreeWidget
     Q_OBJECT
 
 public:
-    explicit CoinControlTreeWidget(QWidget *parent = 0);
+    explicit CoinControlTreeWidget(QWidget *parent = nullptr);
 
 protected:
     virtual void keyPressEvent(QKeyEvent *event);
diff --git a/src/qt/csvmodelwriter.cpp b/src/qt/csvmodelwriter.cpp
index fe63fed52c..656afb6e87 100644
--- a/src/qt/csvmodelwriter.cpp
+++ b/src/qt/csvmodelwriter.cpp
@@ -10,7 +10,7 @@
 
 CSVModelWriter::CSVModelWriter(const QString &_filename, QObject *parent) :
     QObject(parent),
-    filename(_filename), model(0)
+    filename(_filename), model(nullptr)
 {
 }
 
diff --git a/src/qt/csvmodelwriter.h b/src/qt/csvmodelwriter.h
index edea369ad1..e8611bea35 100644
--- a/src/qt/csvmodelwriter.h
+++ b/src/qt/csvmodelwriter.h
@@ -20,7 +20,7 @@ class CSVModelWriter : public QObject
     Q_OBJECT
 
 public:
-    explicit CSVModelWriter(const QString &filename, QObject *parent = 0);
+    explicit CSVModelWriter(const QString &filename, QObject *parent = nullptr);
 
     void setModel(const QAbstractItemModel *model);
     void addColumn(const QString &title, int column, int role=Qt::EditRole);
diff --git a/src/qt/editaddressdialog.cpp b/src/qt/editaddressdialog.cpp
index 0b0b96b30c..4711412ac4 100644
--- a/src/qt/editaddressdialog.cpp
+++ b/src/qt/editaddressdialog.cpp
@@ -15,9 +15,9 @@
 EditAddressDialog::EditAddressDialog(Mode _mode, QWidget *parent) :
     QDialog(parent),
     ui(new Ui::EditAddressDialog),
-    mapper(0),
+    mapper(nullptr),
     mode(_mode),
-    model(0)
+    model(nullptr)
 {
     ui->setupUi(this);
 
diff --git a/src/qt/editaddressdialog.h b/src/qt/editaddressdialog.h
index fd88b45793..4d0e0709be 100644
--- a/src/qt/editaddressdialog.h
+++ b/src/qt/editaddressdialog.h
@@ -30,7 +30,7 @@ class EditAddressDialog : public QDialog
         EditSendingAddress
     };
 
-    explicit EditAddressDialog(Mode mode, QWidget *parent = 0);
+    explicit EditAddressDialog(Mode mode, QWidget *parent = nullptr);
     ~EditAddressDialog();
 
     void setModel(AddressTableModel *model);
diff --git a/src/qt/guiutil.h b/src/qt/guiutil.h
index f1d0aa48ef..ecb770d147 100644
--- a/src/qt/guiutil.h
+++ b/src/qt/guiutil.h
@@ -133,7 +133,7 @@ namespace GUIUtil
         Q_OBJECT
 
     public:
-        explicit ToolTipToRichTextFilter(int size_threshold, QObject *parent = 0);
+        explicit ToolTipToRichTextFilter(int size_threshold, QObject *parent = nullptr);
 
     protected:
         bool eventFilter(QObject *obj, QEvent *evt);
diff --git a/src/qt/intro.cpp b/src/qt/intro.cpp
index a9a6ab9a8e..d9ab907121 100644
--- a/src/qt/intro.cpp
+++ b/src/qt/intro.cpp
@@ -113,7 +113,7 @@ void FreespaceChecker::check()
 Intro::Intro(QWidget *parent, uint64_t blockchain_size, uint64_t chain_state_size) :
     QDialog(parent),
     ui(new Ui::Intro),
-    thread(0),
+    thread(nullptr),
     signalled(false),
     m_blockchain_size(blockchain_size),
     m_chain_state_size(chain_state_size)
diff --git a/src/qt/intro.h b/src/qt/intro.h
index 01c4165f3e..3da8a16114 100644
--- a/src/qt/intro.h
+++ b/src/qt/intro.h
@@ -30,7 +30,7 @@ class Intro : public QDialog
     Q_OBJECT
 
 public:
-    explicit Intro(QWidget *parent = 0,
+    explicit Intro(QWidget *parent = nullptr,
                    uint64_t blockchain_size = 0, uint64_t chain_state_size = 0);
     ~Intro();
 
diff --git a/src/qt/optionsdialog.cpp b/src/qt/optionsdialog.cpp
index c9871f6c66..27cec06d4b 100644
--- a/src/qt/optionsdialog.cpp
+++ b/src/qt/optionsdialog.cpp
@@ -29,8 +29,8 @@
 OptionsDialog::OptionsDialog(QWidget *parent, bool enableWallet) :
     QDialog(parent),
     ui(new Ui::OptionsDialog),
-    model(0),
-    mapper(0)
+    model(nullptr),
+    mapper(nullptr)
 {
     ui->setupUi(this);
 
diff --git a/src/qt/optionsmodel.h b/src/qt/optionsmodel.h
index 2421734527..1af3a72b92 100644
--- a/src/qt/optionsmodel.h
+++ b/src/qt/optionsmodel.h
@@ -31,7 +31,7 @@ class OptionsModel : public QAbstractListModel
     Q_OBJECT
 
 public:
-    explicit OptionsModel(interfaces::Node& node, QObject *parent = 0, bool resetSettings = false);
+    explicit OptionsModel(interfaces::Node& node, QObject *parent = nullptr, bool resetSettings = false);
 
     enum OptionID {
         StartAtStartup,         // bool
diff --git a/src/qt/overviewpage.cpp b/src/qt/overviewpage.cpp
index bec79335e7..d8e48f350a 100644
--- a/src/qt/overviewpage.cpp
+++ b/src/qt/overviewpage.cpp
@@ -113,8 +113,8 @@ class TxViewDelegate : public QAbstractItemDelegate
 OverviewPage::OverviewPage(const PlatformStyle *platformStyle, QWidget *parent) :
     QWidget(parent),
     ui(new Ui::OverviewPage),
-    clientModel(0),
-    walletModel(0),
+    clientModel(nullptr),
+    walletModel(nullptr),
     txdelegate(new TxViewDelegate(platformStyle, this))
 {
     ui->setupUi(this);
diff --git a/src/qt/overviewpage.h b/src/qt/overviewpage.h
index 75100ae6f7..00ba7ad4ce 100644
--- a/src/qt/overviewpage.h
+++ b/src/qt/overviewpage.h
@@ -30,7 +30,7 @@ class OverviewPage : public QWidget
     Q_OBJECT
 
 public:
-    explicit OverviewPage(const PlatformStyle *platformStyle, QWidget *parent = 0);
+    explicit OverviewPage(const PlatformStyle *platformStyle, QWidget *parent = nullptr);
     ~OverviewPage();
 
     void setClientModel(ClientModel *clientModel);
diff --git a/src/qt/paymentserver.cpp b/src/qt/paymentserver.cpp
index 8148986b51..cfd54c330b 100644
--- a/src/qt/paymentserver.cpp
+++ b/src/qt/paymentserver.cpp
@@ -194,10 +194,10 @@ bool PaymentServer::ipcSendCommandLine()
 PaymentServer::PaymentServer(QObject* parent, bool startLocalServer) :
     QObject(parent),
     saveURIs(true),
-    uriServer(0),
-    optionsModel(0)
+    uriServer(nullptr),
+    optionsModel(nullptr)
 #ifdef ENABLE_BIP70
-    ,netManager(0)
+    ,netManager(nullptr)
 #endif
 {
 #ifdef ENABLE_BIP70
diff --git a/src/qt/peertablemodel.h b/src/qt/peertablemodel.h
index 738a06496f..b3f5dd7dbe 100644
--- a/src/qt/peertablemodel.h
+++ b/src/qt/peertablemodel.h
@@ -51,7 +51,7 @@ class PeerTableModel : public QAbstractTableModel
     Q_OBJECT
 
 public:
-    explicit PeerTableModel(interfaces::Node& node, ClientModel *parent = 0);
+    explicit PeerTableModel(interfaces::Node& node, ClientModel *parent = nullptr);
     ~PeerTableModel();
     const CNodeCombinedStats *getNodeStats(int idx);
     int getRowByNodeId(NodeId nodeid);
diff --git a/src/qt/qvaluecombobox.h b/src/qt/qvaluecombobox.h
index f266302310..8892071fba 100644
--- a/src/qt/qvaluecombobox.h
+++ b/src/qt/qvaluecombobox.h
@@ -16,7 +16,7 @@ class QValueComboBox : public QComboBox
     Q_PROPERTY(QVariant value READ value WRITE setValue NOTIFY valueChanged USER true)
 
 public:
-    explicit QValueComboBox(QWidget *parent = 0);
+    explicit QValueComboBox(QWidget *parent = nullptr);
 
     QVariant value() const;
     void setValue(const QVariant &value);
diff --git a/src/qt/receivecoinsdialog.cpp b/src/qt/receivecoinsdialog.cpp
index a7cc5da19e..bc96b5a6f7 100644
--- a/src/qt/receivecoinsdialog.cpp
+++ b/src/qt/receivecoinsdialog.cpp
@@ -25,8 +25,8 @@
 ReceiveCoinsDialog::ReceiveCoinsDialog(const PlatformStyle *_platformStyle, QWidget *parent) :
     QDialog(parent),
     ui(new Ui::ReceiveCoinsDialog),
-    columnResizingFixer(0),
-    model(0),
+    columnResizingFixer(nullptr),
+    model(nullptr),
     platformStyle(_platformStyle)
 {
     ui->setupUi(this);
diff --git a/src/qt/receivecoinsdialog.h b/src/qt/receivecoinsdialog.h
index bc0f6248f0..5bca2f46e2 100644
--- a/src/qt/receivecoinsdialog.h
+++ b/src/qt/receivecoinsdialog.h
@@ -39,7 +39,7 @@ class ReceiveCoinsDialog : public QDialog
         MINIMUM_COLUMN_WIDTH = 130
     };
 
-    explicit ReceiveCoinsDialog(const PlatformStyle *platformStyle, QWidget *parent = 0);
+    explicit ReceiveCoinsDialog(const PlatformStyle *platformStyle, QWidget *parent = nullptr);
     ~ReceiveCoinsDialog();
 
     void setModel(WalletModel *model);
diff --git a/src/qt/receiverequestdialog.cpp b/src/qt/receiverequestdialog.cpp
index c561d948be..f5b30cf6d2 100644
--- a/src/qt/receiverequestdialog.cpp
+++ b/src/qt/receiverequestdialog.cpp
@@ -26,7 +26,7 @@
 #endif
 
 QRImageWidget::QRImageWidget(QWidget *parent):
-    QLabel(parent), contextMenu(0)
+    QLabel(parent), contextMenu(nullptr)
 {
     contextMenu = new QMenu(this);
     QAction *saveImageAction = new QAction(tr("&Save Image..."), this);
@@ -88,7 +88,7 @@ void QRImageWidget::contextMenuEvent(QContextMenuEvent *event)
 ReceiveRequestDialog::ReceiveRequestDialog(QWidget *parent) :
     QDialog(parent),
     ui(new Ui::ReceiveRequestDialog),
-    model(0)
+    model(nullptr)
 {
     ui->setupUi(this);
 
diff --git a/src/qt/receiverequestdialog.h b/src/qt/receiverequestdialog.h
index 5662af18b7..dd28fd73c8 100644
--- a/src/qt/receiverequestdialog.h
+++ b/src/qt/receiverequestdialog.h
@@ -28,7 +28,7 @@ class QRImageWidget : public QLabel
     Q_OBJECT
 
 public:
-    explicit QRImageWidget(QWidget *parent = 0);
+    explicit QRImageWidget(QWidget *parent = nullptr);
     QImage exportImage();
 
 public Q_SLOTS:
@@ -48,7 +48,7 @@ class ReceiveRequestDialog : public QDialog
     Q_OBJECT
 
 public:
-    explicit ReceiveRequestDialog(QWidget *parent = 0);
+    explicit ReceiveRequestDialog(QWidget *parent = nullptr);
     ~ReceiveRequestDialog();
 
     void setModel(WalletModel *model);
diff --git a/src/qt/sendcoinsdialog.cpp b/src/qt/sendcoinsdialog.cpp
index 65db0280b7..6e00ab755c 100644
--- a/src/qt/sendcoinsdialog.cpp
+++ b/src/qt/sendcoinsdialog.cpp
@@ -54,8 +54,8 @@ int getIndexForConfTarget(int target) {
 SendCoinsDialog::SendCoinsDialog(const PlatformStyle *_platformStyle, QWidget *parent) :
     QDialog(parent),
     ui(new Ui::SendCoinsDialog),
-    clientModel(0),
-    model(0),
+    clientModel(nullptr),
+    model(nullptr),
     fNewRecipientAllowed(true),
     fFeeMinimized(true),
     platformStyle(_platformStyle)
@@ -443,7 +443,7 @@ SendCoinsEntry *SendCoinsDialog::addEntry()
 
 void SendCoinsDialog::updateTabsAndLabels()
 {
-    setupTabChain(0);
+    setupTabChain(nullptr);
     coinControlUpdateLabels();
 }
 
@@ -478,7 +478,7 @@ QWidget *SendCoinsDialog::setupTabChain(QWidget *prev)
 
 void SendCoinsDialog::setAddress(const QString &address)
 {
-    SendCoinsEntry *entry = 0;
+    SendCoinsEntry *entry = nullptr;
     // Replace the first entry if it is still unused
     if(ui->entries->count() == 1)
     {
@@ -501,7 +501,7 @@ void SendCoinsDialog::pasteEntry(const SendCoinsRecipient &rv)
     if(!fNewRecipientAllowed)
         return;
 
-    SendCoinsEntry *entry = 0;
+    SendCoinsEntry *entry = nullptr;
     // Replace the first entry if it is still unused
     if(ui->entries->count() == 1)
     {
diff --git a/src/qt/sendcoinsdialog.h b/src/qt/sendcoinsdialog.h
index e1ebc77d59..337a72b878 100644
--- a/src/qt/sendcoinsdialog.h
+++ b/src/qt/sendcoinsdialog.h
@@ -31,7 +31,7 @@ class SendCoinsDialog : public QDialog
     Q_OBJECT
 
 public:
-    explicit SendCoinsDialog(const PlatformStyle *platformStyle, QWidget *parent = 0);
+    explicit SendCoinsDialog(const PlatformStyle *platformStyle, QWidget *parent = nullptr);
     ~SendCoinsDialog();
 
     void setClientModel(ClientModel *clientModel);
@@ -108,7 +108,7 @@ class SendConfirmationDialog : public QMessageBox
     Q_OBJECT
 
 public:
-    SendConfirmationDialog(const QString &title, const QString &text, int secDelay = SEND_CONFIRM_DELAY, QWidget *parent = 0);
+    SendConfirmationDialog(const QString &title, const QString &text, int secDelay = SEND_CONFIRM_DELAY, QWidget *parent = nullptr);
     int exec();
 
 private Q_SLOTS:
diff --git a/src/qt/sendcoinsentry.cpp b/src/qt/sendcoinsentry.cpp
index 76c942c8b9..ab7a5aa956 100644
--- a/src/qt/sendcoinsentry.cpp
+++ b/src/qt/sendcoinsentry.cpp
@@ -21,7 +21,7 @@
 SendCoinsEntry::SendCoinsEntry(const PlatformStyle *_platformStyle, QWidget *parent) :
     QStackedWidget(parent),
     ui(new Ui::SendCoinsEntry),
-    model(0),
+    model(nullptr),
     platformStyle(_platformStyle)
 {
     ui->setupUi(this);
diff --git a/src/qt/sendcoinsentry.h b/src/qt/sendcoinsentry.h
index 48ecd598d6..42e2217130 100644
--- a/src/qt/sendcoinsentry.h
+++ b/src/qt/sendcoinsentry.h
@@ -26,7 +26,7 @@ class SendCoinsEntry : public QStackedWidget
     Q_OBJECT
 
 public:
-    explicit SendCoinsEntry(const PlatformStyle *platformStyle, QWidget *parent = 0);
+    explicit SendCoinsEntry(const PlatformStyle *platformStyle, QWidget *parent = nullptr);
     ~SendCoinsEntry();
 
     void setModel(WalletModel *model);
diff --git a/src/qt/signverifymessagedialog.cpp b/src/qt/signverifymessagedialog.cpp
index 487fc9ee1e..d37a78fa8c 100644
--- a/src/qt/signverifymessagedialog.cpp
+++ b/src/qt/signverifymessagedialog.cpp
@@ -22,7 +22,7 @@
 SignVerifyMessageDialog::SignVerifyMessageDialog(const PlatformStyle *_platformStyle, QWidget *parent) :
     QDialog(parent),
     ui(new Ui::SignVerifyMessageDialog),
-    model(0),
+    model(nullptr),
     platformStyle(_platformStyle)
 {
     ui->setupUi(this);
diff --git a/src/qt/trafficgraphwidget.cpp b/src/qt/trafficgraphwidget.cpp
index 3aed3f2b97..1588be8da3 100644
--- a/src/qt/trafficgraphwidget.cpp
+++ b/src/qt/trafficgraphwidget.cpp
@@ -19,14 +19,14 @@
 
 TrafficGraphWidget::TrafficGraphWidget(QWidget *parent) :
     QWidget(parent),
-    timer(0),
+    timer(nullptr),
     fMax(0.0f),
     nMins(0),
     vSamplesIn(),
     vSamplesOut(),
     nLastBytesIn(0),
     nLastBytesOut(0),
-    clientModel(0)
+    clientModel(nullptr)
 {
     timer = new QTimer(this);
     connect(timer, &QTimer::timeout, this, &TrafficGraphWidget::updateRates);
diff --git a/src/qt/trafficgraphwidget.h b/src/qt/trafficgraphwidget.h
index 00660574af..48bd246b34 100644
--- a/src/qt/trafficgraphwidget.h
+++ b/src/qt/trafficgraphwidget.h
@@ -20,7 +20,7 @@ class TrafficGraphWidget : public QWidget
     Q_OBJECT
 
 public:
-    explicit TrafficGraphWidget(QWidget *parent = 0);
+    explicit TrafficGraphWidget(QWidget *parent = nullptr);
     void setClientModel(ClientModel *model);
     int getGraphRangeMins() const;
 
diff --git a/src/qt/transactiondescdialog.h b/src/qt/transactiondescdialog.h
index f1371b3856..8fd3f3166a 100644
--- a/src/qt/transactiondescdialog.h
+++ b/src/qt/transactiondescdialog.h
@@ -21,7 +21,7 @@ class TransactionDescDialog : public QDialog
     Q_OBJECT
 
 public:
-    explicit TransactionDescDialog(const QModelIndex &idx, QWidget *parent = 0);
+    explicit TransactionDescDialog(const QModelIndex &idx, QWidget *parent = nullptr);
     ~TransactionDescDialog();
 
 private:
diff --git a/src/qt/transactionfilterproxy.h b/src/qt/transactionfilterproxy.h
index 9febd59820..685f8d3a26 100644
--- a/src/qt/transactionfilterproxy.h
+++ b/src/qt/transactionfilterproxy.h
@@ -16,7 +16,7 @@ class TransactionFilterProxy : public QSortFilterProxyModel
     Q_OBJECT
 
 public:
-    explicit TransactionFilterProxy(QObject *parent = 0);
+    explicit TransactionFilterProxy(QObject *parent = nullptr);
 
     /** Earliest date that can be represented (far in the past) */
     static const QDateTime MIN_DATE;
diff --git a/src/qt/transactiontablemodel.h b/src/qt/transactiontablemodel.h
index 8be3a7ab2e..7a7d98962b 100644
--- a/src/qt/transactiontablemodel.h
+++ b/src/qt/transactiontablemodel.h
@@ -28,7 +28,7 @@ class TransactionTableModel : public QAbstractTableModel
     Q_OBJECT
 
 public:
-    explicit TransactionTableModel(const PlatformStyle *platformStyle, WalletModel *parent = 0);
+    explicit TransactionTableModel(const PlatformStyle *platformStyle, WalletModel *parent = nullptr);
     ~TransactionTableModel();
 
     enum ColumnIndex {
diff --git a/src/qt/transactionview.cpp b/src/qt/transactionview.cpp
index 68410c8bd6..eb6437eb31 100644
--- a/src/qt/transactionview.cpp
+++ b/src/qt/transactionview.cpp
@@ -38,8 +38,8 @@
 #include <QVBoxLayout>
 
 TransactionView::TransactionView(const PlatformStyle *platformStyle, QWidget *parent) :
-    QWidget(parent), model(0), transactionProxyModel(0),
-    transactionView(0), abandonAction(0), bumpFeeAction(0), columnResizingFixer(0)
+    QWidget(parent), model(nullptr), transactionProxyModel(nullptr),
+    transactionView(nullptr), abandonAction(nullptr), bumpFeeAction(nullptr), columnResizingFixer(nullptr)
 {
     // Build filter row
     setContentsMargins(0,0,0,0);
diff --git a/src/qt/transactionview.h b/src/qt/transactionview.h
index fdd8b069c7..e07181d1c8 100644
--- a/src/qt/transactionview.h
+++ b/src/qt/transactionview.h
@@ -35,7 +35,7 @@ class TransactionView : public QWidget
     Q_OBJECT
 
 public:
-    explicit TransactionView(const PlatformStyle *platformStyle, QWidget *parent = 0);
+    explicit TransactionView(const PlatformStyle *platformStyle, QWidget *parent = nullptr);
 
     void setModel(WalletModel *model);
 
diff --git a/src/qt/utilitydialog.h b/src/qt/utilitydialog.h
index ad1fda4573..f0e01bc571 100644
--- a/src/qt/utilitydialog.h
+++ b/src/qt/utilitydialog.h
@@ -45,7 +45,7 @@ class ShutdownWindow : public QWidget
     Q_OBJECT
 
 public:
-    explicit ShutdownWindow(QWidget *parent=0, Qt::WindowFlags f=0);
+    explicit ShutdownWindow(QWidget *parent=nullptr, Qt::WindowFlags f=0);
     static QWidget *showShutdownWindow(BitcoinGUI *window);
 
 protected:
diff --git a/src/qt/walletframe.h b/src/qt/walletframe.h
index 9fbc8b4d52..10d063b2b7 100644
--- a/src/qt/walletframe.h
+++ b/src/qt/walletframe.h
@@ -31,7 +31,7 @@ class WalletFrame : public QFrame
     Q_OBJECT
 
 public:
-    explicit WalletFrame(const PlatformStyle *platformStyle, BitcoinGUI *_gui = 0);
+    explicit WalletFrame(const PlatformStyle *platformStyle, BitcoinGUI *_gui = nullptr);
     ~WalletFrame();
 
     void setClientModel(ClientModel *clientModel);
diff --git a/src/qt/walletmodel.cpp b/src/qt/walletmodel.cpp
index 0a5b21f997..d909cc837c 100644
--- a/src/qt/walletmodel.cpp
+++ b/src/qt/walletmodel.cpp
@@ -33,9 +33,9 @@
 
 
 WalletModel::WalletModel(std::unique_ptr<interfaces::Wallet> wallet, interfaces::Node& node, const PlatformStyle *platformStyle, OptionsModel *_optionsModel, QObject *parent) :
-    QObject(parent), m_wallet(std::move(wallet)), m_node(node), optionsModel(_optionsModel), addressTableModel(0),
-    transactionTableModel(0),
-    recentRequestsTableModel(0),
+    QObject(parent), m_wallet(std::move(wallet)), m_node(node), optionsModel(_optionsModel), addressTableModel(nullptr),
+    transactionTableModel(nullptr),
+    recentRequestsTableModel(nullptr),
     cachedEncryptionStatus(Unencrypted),
     cachedNumBlocks(0)
 {
diff --git a/src/qt/walletmodel.h b/src/qt/walletmodel.h
index 6a6c538157..c3c8f36909 100644
--- a/src/qt/walletmodel.h
+++ b/src/qt/walletmodel.h
@@ -127,7 +127,7 @@ class WalletModel : public QObject
     Q_OBJECT
 
 public:
-    explicit WalletModel(std::unique_ptr<interfaces::Wallet> wallet, interfaces::Node& node, const PlatformStyle *platformStyle, OptionsModel *optionsModel, QObject *parent = 0);
+    explicit WalletModel(std::unique_ptr<interfaces::Wallet> wallet, interfaces::Node& node, const PlatformStyle *platformStyle, OptionsModel *optionsModel, QObject *parent = nullptr);
     ~WalletModel();
 
     enum StatusCode // Returned by sendCoins
diff --git a/src/qt/walletview.cpp b/src/qt/walletview.cpp
index a619992344..dd089d8310 100644
--- a/src/qt/walletview.cpp
+++ b/src/qt/walletview.cpp
@@ -32,8 +32,8 @@
 
 WalletView::WalletView(const PlatformStyle *_platformStyle, QWidget *parent):
     QStackedWidget(parent),
-    clientModel(0),
-    walletModel(0),
+    clientModel(nullptr),
+    walletModel(nullptr),
     platformStyle(_platformStyle)
 {
     // Create tabs