diff --git a/src/lib/plugins/qml/api/bookmarks/qmlbookmarks.cpp b/src/lib/plugins/qml/api/bookmarks/qmlbookmarks.cpp
index 66a154f52..9f11643cd 100644
--- a/src/lib/plugins/qml/api/bookmarks/qmlbookmarks.cpp
+++ b/src/lib/plugins/qml/api/bookmarks/qmlbookmarks.cpp
@@ -126,9 +126,9 @@ bool QmlBookmarks::create(const QVariantMap &map) const
         qWarning() << "Unable to create new bookmark:" << "parent not found";
         return false;
     }
-    QString title = map.value(QSL("title")).toString();
-    QString urlString = map.value(QSL("url")).toString();
-    QString description = map.value(QSL("description")).toString();
+    const QString title = map.value(QSL("title")).toString();
+    const QString urlString = map.value(QSL("url")).toString();
+    const QString description = map.value(QSL("description")).toString();
 
     BookmarkItem::Type type;
     if (map.contains(QSL("type"))) {
@@ -175,8 +175,8 @@ QList<QObject*> QmlBookmarks::search(const QVariantMap &map) const
         return QList<QObject*>();
     }
 
-    QString query = map.value(QSL("query")).toString();
-    QString urlString = map.value(QSL("url")).toString();
+    const QString query = map.value(QSL("query")).toString();
+    const QString urlString = map.value(QSL("url")).toString();
     QList<BookmarkItem*> items;
     if (urlString.isEmpty()) {
         items = mApp->bookmarks()->searchBookmarks(query);
diff --git a/src/lib/plugins/qml/api/bookmarks/qmlbookmarks.h b/src/lib/plugins/qml/api/bookmarks/qmlbookmarks.h
index 034c8930e..88b07d810 100644
--- a/src/lib/plugins/qml/api/bookmarks/qmlbookmarks.h
+++ b/src/lib/plugins/qml/api/bookmarks/qmlbookmarks.h
@@ -27,7 +27,7 @@ class QmlBookmarks : public QObject
     Q_OBJECT
 
 public:
-    explicit QmlBookmarks(QObject *parent = 0);
+    explicit QmlBookmarks(QObject *parent = nullptr);
 
     Q_INVOKABLE bool isBookmarked(const QUrl &url) const;
     Q_INVOKABLE QmlBookmarkTreeNode *rootItem() const;
diff --git a/src/lib/plugins/qml/api/bookmarks/qmlbookmarktreenode.cpp b/src/lib/plugins/qml/api/bookmarks/qmlbookmarktreenode.cpp
index 21b7dbf8e..f3d1cba38 100644
--- a/src/lib/plugins/qml/api/bookmarks/qmlbookmarktreenode.cpp
+++ b/src/lib/plugins/qml/api/bookmarks/qmlbookmarktreenode.cpp
@@ -114,9 +114,9 @@ bool QmlBookmarkTreeNode::unmodifiable() const
 
 QList<QObject*> QmlBookmarkTreeNode::children() const
 {
-    auto items = m_item->children();
+    const auto items = m_item->children();
     QList<QObject*> ret;
-    for (auto item : items) {
+    for (const auto &item : items) {
         ret.append(bookmarkTreeNodeData->get(item));
     }
     return ret;
@@ -128,9 +128,7 @@ QmlBookmarkTreeNodeData::QmlBookmarkTreeNodeData()
 
 QmlBookmarkTreeNodeData::~QmlBookmarkTreeNodeData()
 {
-    for (QmlBookmarkTreeNode *node : m_nodes.values()) {
-        node->deleteLater();
-    }
+    qDeleteAll(m_nodes);
 }
 
 QmlBookmarkTreeNode *QmlBookmarkTreeNodeData::get(BookmarkItem *item)
diff --git a/src/lib/plugins/qml/api/clipboard/qmlclipboard.h b/src/lib/plugins/qml/api/clipboard/qmlclipboard.h
index 21c23e913..64978cf43 100644
--- a/src/lib/plugins/qml/api/clipboard/qmlclipboard.h
+++ b/src/lib/plugins/qml/api/clipboard/qmlclipboard.h
@@ -23,6 +23,6 @@ class QmlClipboard : public QObject
 {
     Q_OBJECT
 public:
-    explicit QmlClipboard(QObject *parent = 0);
+    explicit QmlClipboard(QObject *parent = nullptr);
     Q_INVOKABLE void copy(const QVariantMap &map);
 };
diff --git a/src/lib/plugins/qml/api/cookies/qmlcookie.cpp b/src/lib/plugins/qml/api/cookies/qmlcookie.cpp
index 7d12535d3..608f65a58 100644
--- a/src/lib/plugins/qml/api/cookies/qmlcookie.cpp
+++ b/src/lib/plugins/qml/api/cookies/qmlcookie.cpp
@@ -88,9 +88,7 @@ QmlCookieData::QmlCookieData()
 
 QmlCookieData::~QmlCookieData()
 {
-    for (QmlCookie *qmlCookie : m_cookies.values()) {
-        qmlCookie->deleteLater();
-    }
+    qDeleteAll(m_cookies);
 }
 
 QmlCookie *QmlCookieData::get(QNetworkCookie *cookie)
diff --git a/src/lib/plugins/qml/api/cookies/qmlcookie.h b/src/lib/plugins/qml/api/cookies/qmlcookie.h
index 4e454c246..581c80b5c 100644
--- a/src/lib/plugins/qml/api/cookies/qmlcookie.h
+++ b/src/lib/plugins/qml/api/cookies/qmlcookie.h
@@ -32,7 +32,7 @@ class QmlCookie : public QObject
     Q_PROPERTY(bool session READ session CONSTANT)
     Q_PROPERTY(QString value READ value CONSTANT)
 public:
-    explicit QmlCookie(QNetworkCookie *cookie = 0, QObject *parent = 0);
+    explicit QmlCookie(QNetworkCookie *cookie = nullptr, QObject *parent = nullptr);
     QString domain() const;
     QDateTime expirationDate() const;
     QString name() const;
diff --git a/src/lib/plugins/qml/api/cookies/qmlcookies.cpp b/src/lib/plugins/qml/api/cookies/qmlcookies.cpp
index 3bb0521fb..3fd1b4a08 100644
--- a/src/lib/plugins/qml/api/cookies/qmlcookies.cpp
+++ b/src/lib/plugins/qml/api/cookies/qmlcookies.cpp
@@ -50,10 +50,10 @@ QNetworkCookie *QmlCookies::getNetworkCookie(const QVariantMap &map)
         qWarning() << "Error:" << "Wrong arguments passed to" << __FUNCTION__;
         return nullptr;
     }
-    QString name = map.value(QSL("name")).toString();
-    QString url = map.value(QSL("url")).toString();
+    const QString name = map.value(QSL("name")).toString();
+    const QString url = map.value(QSL("url")).toString();
     QVector<QNetworkCookie> cookies = mApp->cookieJar()->getAllCookies();
-    for (QNetworkCookie cookie : cookies) {
+    for (const QNetworkCookie &cookie : cookies) {
         if (cookie.name() == name && cookie.domain() == url) {
             QNetworkCookie *netCookie = new QNetworkCookie(cookie);
             return netCookie;
@@ -74,11 +74,11 @@ QmlCookie *QmlCookies::get(const QVariantMap &map)
 QList<QObject*> QmlCookies::getAll(const QVariantMap &map)
 {
     QList<QObject*> qmlCookies;
-    QString name = map.value(QSL("name")).toString();
-    QString url = map.value(QSL("url")).toString();
-    QString path = map.value(QSL("path")).toString();
-    bool secure = map.value(QSL("secure")).toBool();
-    bool session = map.value(QSL("session")).toBool();
+    const QString name = map.value(QSL("name")).toString();
+    const QString url = map.value(QSL("url")).toString();
+    const QString path = map.value(QSL("path")).toString();
+    const bool secure = map.value(QSL("secure")).toBool();
+    const bool session = map.value(QSL("session")).toBool();
     QVector<QNetworkCookie> cookies = mApp->cookieJar()->getAllCookies();
     for (QNetworkCookie cookie : cookies) {
         if ((!map.contains(QSL("name")) || cookie.name() == name)
@@ -96,13 +96,13 @@ QList<QObject*> QmlCookies::getAll(const QVariantMap &map)
 
 void QmlCookies::set(const QVariantMap &map)
 {
-    QString name = map.value(QSL("name")).toString();
-    QString url = map.value(QSL("url")).toString();
-    QString path = map.value(QSL("path")).toString();
-    bool secure = map.value(QSL("secure")).toBool();
-    QDateTime expirationDate = QDateTime::fromMSecsSinceEpoch(map.value(QSL("expirationDate")).toDouble());
-    bool httpOnly = map.value(QSL("httpOnly")).toBool();
-    QString value = map.value(QSL("value")).toString();
+    const QString name = map.value(QSL("name")).toString();
+    const QString url = map.value(QSL("url")).toString();
+    const QString path = map.value(QSL("path")).toString();
+    const bool secure = map.value(QSL("secure")).toBool();
+    const QDateTime expirationDate = QDateTime::fromMSecsSinceEpoch(map.value(QSL("expirationDate")).toDouble());
+    const bool httpOnly = map.value(QSL("httpOnly")).toBool();
+    const QString value = map.value(QSL("value")).toString();
     QNetworkCookie cookie;
     cookie.setName(name.toUtf8());
     cookie.setDomain(url);
diff --git a/src/lib/plugins/qml/api/cookies/qmlcookies.h b/src/lib/plugins/qml/api/cookies/qmlcookies.h
index 96ac173ef..2dc2b1b0f 100644
--- a/src/lib/plugins/qml/api/cookies/qmlcookies.h
+++ b/src/lib/plugins/qml/api/cookies/qmlcookies.h
@@ -24,7 +24,7 @@ class QmlCookies : public QObject
 {
     Q_OBJECT
 public:
-    explicit QmlCookies(QObject *parent = 0);
+    explicit QmlCookies(QObject *parent = nullptr);
     Q_INVOKABLE QmlCookie *get(const QVariantMap &map);
     Q_INVOKABLE QList<QObject*> getAll(const QVariantMap &map);
     Q_INVOKABLE void set(const QVariantMap &map);
diff --git a/src/lib/plugins/qml/api/history/qmlhistory.cpp b/src/lib/plugins/qml/api/history/qmlhistory.cpp
index 49bfd9872..b82ed1278 100644
--- a/src/lib/plugins/qml/api/history/qmlhistory.cpp
+++ b/src/lib/plugins/qml/api/history/qmlhistory.cpp
@@ -43,7 +43,7 @@ QList<QObject*> QmlHistory::search(const QVariantMap &map)
         qWarning() << "Error:" << "wrong arguments passed to" << __FUNCTION__;
         return list;
     }
-    QString text = map.value(QSL("text")).toString();
+    const QString text = map.value(QSL("text")).toString();
     QList<HistoryEntry*> result = mApp->history()->searchHistoryEntry(text);
 
     foreach(auto entry, result) {
@@ -59,7 +59,7 @@ int QmlHistory::getVisits(const QVariantMap &map)
         qWarning() << "Error:" << "wrong arguments passed to" << __FUNCTION__;
         return 0;
     }
-    QString url = map.value(QSL("url")).toString();
+    const QString url = map.value(QSL("url")).toString();
     HistoryEntry *entry = mApp->history()->getHistoryEntry(url);
     return entry->count;
 }
@@ -71,7 +71,7 @@ void QmlHistory::addUrl(const QVariantMap &map)
         return;
     }
     QString title = map.value(QSL("title")).toString();
-    QString url = map.value(QSL("url")).toString();
+    const QString url = map.value(QSL("url")).toString();
 
     title = title.isEmpty() ? url : title;
 
@@ -84,7 +84,7 @@ void QmlHistory::deleteUrl(const QVariantMap &map)
         qWarning() << "Error:" << "wrong arguments passed to" << __FUNCTION__;
         return;
     }
-    QString url = map.value(QSL("url")).toString();
+    const QString url = map.value(QSL("url")).toString();
     mApp->history()->deleteHistoryEntry(url);
 }
 
@@ -94,8 +94,8 @@ void QmlHistory::deleteRange(const QVariantMap &map)
         qWarning() << "Error:" << "wrong arguments passed to" << __FUNCTION__;
         return;
     }
-    double startTime = map.value(QSL("startTime")).toDouble();
-    double endTime = map.value(QSL("endTime")).toDouble();
+    const double startTime = map.value(QSL("startTime")).toDouble();
+    const double endTime = map.value(QSL("endTime")).toDouble();
     mApp->history()->deleteRange(startTime, endTime);
 }
 
diff --git a/src/lib/plugins/qml/api/history/qmlhistory.h b/src/lib/plugins/qml/api/history/qmlhistory.h
index 57107a0d6..766ead0d5 100644
--- a/src/lib/plugins/qml/api/history/qmlhistory.h
+++ b/src/lib/plugins/qml/api/history/qmlhistory.h
@@ -24,7 +24,7 @@ class QmlHistory : public QObject
 {
     Q_OBJECT
 public:
-    explicit QmlHistory(QObject *parent = 0);
+    explicit QmlHistory(QObject *parent = nullptr);
     Q_INVOKABLE QList<QObject*> search(const QVariantMap &map);
     Q_INVOKABLE int getVisits(const QVariantMap &map);
     Q_INVOKABLE void addUrl(const QVariantMap &map);
diff --git a/src/lib/plugins/qml/api/history/qmlhistoryitem.cpp b/src/lib/plugins/qml/api/history/qmlhistoryitem.cpp
index d92ba9ff5..08b6bc137 100644
--- a/src/lib/plugins/qml/api/history/qmlhistoryitem.cpp
+++ b/src/lib/plugins/qml/api/history/qmlhistoryitem.cpp
@@ -71,9 +71,7 @@ QmlHistoryItemData::QmlHistoryItemData()
 
 QmlHistoryItemData::~QmlHistoryItemData()
 {
-    for (QmlHistoryItem *item : m_items.values()) {
-        item->deleteLater();
-    }
+    qDeleteAll(m_items);
 }
 
 QmlHistoryItem *QmlHistoryItemData::get(HistoryEntry *entry)
diff --git a/src/lib/plugins/qml/api/history/qmlhistoryitem.h b/src/lib/plugins/qml/api/history/qmlhistoryitem.h
index cbca677f9..0f3e8235a 100644
--- a/src/lib/plugins/qml/api/history/qmlhistoryitem.h
+++ b/src/lib/plugins/qml/api/history/qmlhistoryitem.h
@@ -29,7 +29,7 @@ class QmlHistoryItem : public QObject
     Q_PROPERTY(int visitCount READ visitCount CONSTANT)
     Q_PROPERTY(QDateTime lastVisitTime READ lastVisitTime CONSTANT)
 public:
-    explicit QmlHistoryItem(HistoryEntry *entry = 0, QObject *parent = 0);
+    explicit QmlHistoryItem(HistoryEntry *entry = nullptr, QObject *parent = nullptr);
     int id() const;
     QString url() const;
     QString title() const;
diff --git a/src/lib/plugins/qml/api/notifications/qmlnotifications.h b/src/lib/plugins/qml/api/notifications/qmlnotifications.h
index 823cbd86c..48bdde52a 100644
--- a/src/lib/plugins/qml/api/notifications/qmlnotifications.h
+++ b/src/lib/plugins/qml/api/notifications/qmlnotifications.h
@@ -23,6 +23,6 @@ class QmlNotifications : public QObject
 {
     Q_OBJECT
 public:
-    explicit QmlNotifications(QObject *parent = 0);
+    explicit QmlNotifications(QObject *parent = nullptr);
     Q_INVOKABLE void create(const QVariantMap &map);
 };
diff --git a/src/lib/plugins/qml/api/tabs/qmltab.cpp b/src/lib/plugins/qml/api/tabs/qmltab.cpp
index 66af2e61d..a4f57b128 100644
--- a/src/lib/plugins/qml/api/tabs/qmltab.cpp
+++ b/src/lib/plugins/qml/api/tabs/qmltab.cpp
@@ -21,6 +21,8 @@
 #include <QWebEngineHistory>
 #include <QQmlEngine>
 
+Q_GLOBAL_STATIC(QmlWindowData, windowData)
+
 QmlTab::QmlTab(WebTab *webTab, QObject *parent)
     : QObject(parent)
     , m_webTab(webTab)
@@ -154,7 +156,7 @@ QmlWindow *QmlTab::browserWindow() const
         return nullptr;
     }
 
-    return new QmlWindow(m_webTab->browserWindow());
+    return windowData->get(m_webTab->browserWindow());
 }
 
 bool QmlTab::loading() const
@@ -264,7 +266,7 @@ void QmlTab::load(const QVariantMap &map)
         return;
     }
 
-    QString url = map.value(QSL("url")).toString();
+    const QString url = map.value(QSL("url")).toString();
     LoadRequest req;
     req.setUrl(QUrl::fromEncoded(url.toUtf8()));
     m_webTab->load(req);
@@ -384,9 +386,7 @@ QmlTabData::QmlTabData()
 
 QmlTabData::~QmlTabData()
 {
-    for (QmlTab *tab : m_tabs.values()) {
-        tab->deleteLater();
-    }
+    qDeleteAll(m_tabs);
 }
 
 QmlTab *QmlTabData::get(WebTab *webTab)
diff --git a/src/lib/plugins/qml/api/tabs/qmltab.h b/src/lib/plugins/qml/api/tabs/qmltab.h
index c11d9ddb5..18011bb25 100644
--- a/src/lib/plugins/qml/api/tabs/qmltab.h
+++ b/src/lib/plugins/qml/api/tabs/qmltab.h
@@ -40,7 +40,7 @@ class QmlTab : public QObject
     Q_PROPERTY(bool canGoBack READ canGoBack CONSTANT)
     Q_PROPERTY(bool canGoForward READ canGoForward CONSTANT)
 public:
-    explicit QmlTab(WebTab *webTab = 0, QObject *parent = 0);
+    explicit QmlTab(WebTab *webTab = nullptr, QObject *parent = nullptr);
     QString url() const;
     QString title() const;
     int zoomLevel() const;
diff --git a/src/lib/plugins/qml/api/tabs/qmltabs.cpp b/src/lib/plugins/qml/api/tabs/qmltabs.cpp
index 3e0d06717..2c7feb69d 100644
--- a/src/lib/plugins/qml/api/tabs/qmltabs.cpp
+++ b/src/lib/plugins/qml/api/tabs/qmltabs.cpp
@@ -38,7 +38,7 @@ bool QmlTabs::setCurrentIndex(const QVariantMap &map)
         return false;
     }
 
-    int index = map.value(QSL("index")).toInt();
+    const int index = map.value(QSL("index")).toInt();
 
     const auto window = getWindow(map);
     if (!window) {
@@ -79,8 +79,8 @@ bool QmlTabs::moveTab(const QVariantMap &map)
         return false;
     }
 
-    int from = map.value(QSL("from")).toInt();
-    int to = map.value(QSL("to")).toInt();
+    const int from = map.value(QSL("from")).toInt();
+    const int to = map.value(QSL("to")).toInt();
 
     const auto window = getWindow(map);
     if (!window) {
@@ -97,7 +97,7 @@ bool QmlTabs::pinTab(const QVariantMap &map)
         return false;
     }
 
-    int index = map.value(QSL("index")).toInt();
+    const int index = map.value(QSL("index")).toInt();
 
     const auto window = getWindow(map);
     if (!window) {
@@ -121,7 +121,7 @@ bool QmlTabs::unpinTab(const QVariantMap &map)
         return false;
     }
 
-    int index = map.value(QSL("index")).toInt();
+    const int index = map.value(QSL("index")).toInt();
 
     const auto window = getWindow(map);
     if (!window) {
@@ -145,7 +145,7 @@ bool QmlTabs::detachTab(const QVariantMap &map)
         return false;
     }
 
-    int index = map.value(QSL("index")).toInt();
+    const int index = map.value(QSL("index")).toInt();
 
     const auto window = getWindow(map);
     if (!window) {
@@ -162,7 +162,7 @@ bool QmlTabs::duplicate(const QVariantMap &map)
         return false;
     }
 
-    int index = map.value(QSL("index")).toInt();
+    const int index = map.value(QSL("index")).toInt();
 
     const auto window = getWindow(map);
     if (!window) {
@@ -179,7 +179,7 @@ bool QmlTabs::closeTab(const QVariantMap &map)
         return false;
     }
 
-    int index = map.value(QSL("index")).toInt();
+    const int index = map.value(QSL("index")).toInt();
 
     const auto window = getWindow(map);
     if (!window) {
@@ -196,7 +196,7 @@ bool QmlTabs::reloadTab(const QVariantMap &map)
         return false;
     }
 
-    int index = map.value(QSL("index")).toInt();
+    const int index = map.value(QSL("index")).toInt();
 
     const auto window = getWindow(map);
     if (!window) {
@@ -213,7 +213,7 @@ bool QmlTabs::stopTab(const QVariantMap &map)
         return false;
     }
 
-    int index = map.value(QSL("index")).toInt();
+    const int index = map.value(QSL("index")).toInt();
 
     const auto window = getWindow(map);
     if (!window) {
@@ -230,7 +230,7 @@ QmlTab *QmlTabs::get(const QVariantMap &map) const
         return nullptr;
     }
 
-    int index = map.value(QSL("index")).toInt();
+    const int index = map.value(QSL("index")).toInt();
 
     const auto window = getWindow(map);
     if (!window) {
@@ -265,11 +265,11 @@ QList<QObject*> QmlTabs::getAll(const QVariantMap &map) const
         return QList<QObject*>();
     }
 
-    bool withPinned = map.value(QSL("withPinned")).toBool();
+    const bool withPinned = map.value(QSL("withPinned")).toBool();
     const auto tabList = window->tabWidget()->allTabs(withPinned);
 
     QList<QObject*> list;
-    for (const auto tab : tabList) {
+    for (auto tab : tabList) {
         list.append(tabData->get(tab));
     }
 
@@ -278,9 +278,9 @@ QList<QObject*> QmlTabs::getAll(const QVariantMap &map) const
 
 QList<QObject*> QmlTabs::search(const QVariantMap &map)
 {
-    QString title = map.value(QSL("title")).toString();
-    QString url = map.value(QSL("url")).toString();
-    bool withPinned = map.value(QSL("withPinned")).toBool();
+    const QString title = map.value(QSL("title")).toString();
+    const QString url = map.value(QSL("url")).toString();
+    const bool withPinned = map.value(QSL("withPinned")).toBool();
     QList<QObject*> list;
     foreach (BrowserWindow *window, mApp->windows()) {
         foreach (WebTab *webTab, window->tabWidget()->allTabs(withPinned)) {
@@ -295,7 +295,7 @@ QList<QObject*> QmlTabs::search(const QVariantMap &map)
 
 bool QmlTabs::addTab(const QVariantMap &map)
 {
-    QString urlString = map.value(QSL("url")).toString();
+    const QString urlString = map.value(QSL("url")).toString();
     const auto window = getWindow(map);
     if (!window) {
         qDebug() << "Unable to add tab:" << "window not found";
@@ -303,13 +303,13 @@ bool QmlTabs::addTab(const QVariantMap &map)
     }
     LoadRequest req;
     req.setUrl(QUrl::fromEncoded(urlString.toUtf8()));
-    int ret = window->tabWidget()->addView(req);
+    const int ret = window->tabWidget()->addView(req);
     return ret != -1 ? true : false;
 }
 
 BrowserWindow *QmlTabs::getWindow(const QVariantMap &map) const
 {
-    int windowId = map.value(QSL("windowId"), -1).toInt();
+    const int windowId = map.value(QSL("windowId"), -1).toInt();
     return getWindow(windowId);
 }
 
@@ -331,7 +331,7 @@ BrowserWindow *QmlTabs::getWindow(int windowId) const
 
 void QmlTabs::windowCreated(BrowserWindow *window)
 {
-    int windowId = mApp->windowIdHash().value(window);
+    const int windowId = mApp->windowIdHash().value(window);
 
     connect(window->tabWidget(), &TabWidget::changed, this, [this, windowId]{
         emit changed(windowId);
diff --git a/src/lib/plugins/qml/api/tabs/qmltabs.h b/src/lib/plugins/qml/api/tabs/qmltabs.h
index def6a1678..87b9a48dc 100644
--- a/src/lib/plugins/qml/api/tabs/qmltabs.h
+++ b/src/lib/plugins/qml/api/tabs/qmltabs.h
@@ -25,7 +25,7 @@ class QmlTabs : public QObject
 {
     Q_OBJECT
 public:
-    explicit QmlTabs(QObject *parent = 0);
+    explicit QmlTabs(QObject *parent = nullptr);
     Q_INVOKABLE bool setCurrentIndex(const QVariantMap &map);
     Q_INVOKABLE bool nextTab(int windowId = -1);
     Q_INVOKABLE bool previousTab(int windowId = -1);
diff --git a/src/lib/plugins/qml/api/topsites/qmlmostvisitedurl.cpp b/src/lib/plugins/qml/api/topsites/qmlmostvisitedurl.cpp
index 5963666b1..966bd1dce 100644
--- a/src/lib/plugins/qml/api/topsites/qmlmostvisitedurl.cpp
+++ b/src/lib/plugins/qml/api/topsites/qmlmostvisitedurl.cpp
@@ -18,7 +18,7 @@
 #include "qmlmostvisitedurl.h"
 #include <QQmlEngine>
 
-QmlMostVisitedUrl::QmlMostVisitedUrl(QString title, QString url, QObject *parent)
+QmlMostVisitedUrl::QmlMostVisitedUrl(const QString &title, const QString &url, QObject *parent)
     : QObject(parent)
     , m_title(title)
     , m_url(url)
@@ -42,17 +42,15 @@ QmlMostVisitedUrlData::QmlMostVisitedUrlData()
 
 QmlMostVisitedUrlData::~QmlMostVisitedUrlData()
 {
-    for (QmlMostVisitedUrl *url : m_urls.values()) {
-        url->deleteLater();
-    }
+    qDeleteAll(m_urls);
 }
 
-QmlMostVisitedUrl *QmlMostVisitedUrlData::get(QString title, QString url, QObject *parent)
+QmlMostVisitedUrl *QmlMostVisitedUrlData::get(const QString &title, const QString &url)
 {
-    QmlMostVisitedUrl *visitedUrl = m_urls.value(QPair<QString, QString>(title, url));
+    QmlMostVisitedUrl *visitedUrl = m_urls.value({title, url});
     if (!visitedUrl) {
-        visitedUrl = new QmlMostVisitedUrl(title, url, parent);
-        m_urls.insert(QPair<QString, QString>(title, url), visitedUrl);
+        visitedUrl = new QmlMostVisitedUrl(title, url);
+        m_urls.insert({title, url}, visitedUrl);
     }
     return visitedUrl;
 }
diff --git a/src/lib/plugins/qml/api/topsites/qmlmostvisitedurl.h b/src/lib/plugins/qml/api/topsites/qmlmostvisitedurl.h
index 75148e74c..e3fb3f155 100644
--- a/src/lib/plugins/qml/api/topsites/qmlmostvisitedurl.h
+++ b/src/lib/plugins/qml/api/topsites/qmlmostvisitedurl.h
@@ -27,7 +27,7 @@ class QmlMostVisitedUrl : public QObject
     Q_PROPERTY(QString title READ title CONSTANT)
     Q_PROPERTY(QString url READ url CONSTANT)
 public:
-    explicit QmlMostVisitedUrl(QString title = 0, QString url = 0, QObject *parent = 0);
+    explicit QmlMostVisitedUrl(const QString &title = QString(), const QString &url = QString(), QObject *parent = nullptr);
     QString title() const;
     QString url() const;
 private:
@@ -40,7 +40,7 @@ class QmlMostVisitedUrlData
 public:
     explicit QmlMostVisitedUrlData();
     ~QmlMostVisitedUrlData();
-    QmlMostVisitedUrl *get(QString title = 0, QString url = 0, QObject *parent = 0);
+    QmlMostVisitedUrl *get(const QString &title = QString(), const QString &url = QString());
 private:
     QHash<QPair<QString, QString>, QmlMostVisitedUrl*> m_urls;
 };
diff --git a/src/lib/plugins/qml/api/topsites/qmltopsites.h b/src/lib/plugins/qml/api/topsites/qmltopsites.h
index d99519c96..d3d699c1b 100644
--- a/src/lib/plugins/qml/api/topsites/qmltopsites.h
+++ b/src/lib/plugins/qml/api/topsites/qmltopsites.h
@@ -24,6 +24,6 @@ class QmlTopSites : public QObject
 {
     Q_OBJECT
 public:
-    explicit QmlTopSites(QObject *parent = 0);
+    explicit QmlTopSites(QObject *parent = nullptr);
     Q_INVOKABLE QList<QObject*> get() const;
 };
diff --git a/src/lib/plugins/qml/api/windows/qmlwindow.cpp b/src/lib/plugins/qml/api/windows/qmlwindow.cpp
index e35fe769c..81689928a 100644
--- a/src/lib/plugins/qml/api/windows/qmlwindow.cpp
+++ b/src/lib/plugins/qml/api/windows/qmlwindow.cpp
@@ -134,9 +134,7 @@ QmlWindowData::QmlWindowData()
 
 QmlWindowData::~QmlWindowData()
 {
-    for (QmlWindow *window : m_windows.values()) {
-        window->deleteLater();
-    }
+    qDeleteAll(m_windows);
 }
 
 QmlWindow *QmlWindowData::get(BrowserWindow *window)
diff --git a/src/lib/plugins/qml/api/windows/qmlwindow.h b/src/lib/plugins/qml/api/windows/qmlwindow.h
index 6c42b92d9..066fddee6 100644
--- a/src/lib/plugins/qml/api/windows/qmlwindow.h
+++ b/src/lib/plugins/qml/api/windows/qmlwindow.h
@@ -35,7 +35,7 @@ class QmlWindow : public QObject
     Q_PROPERTY(int height READ height CONSTANT)
     Q_PROPERTY(int width READ width CONSTANT)
 public:
-    QmlWindow(BrowserWindow *window = 0, QObject *parent = 0);
+    QmlWindow(BrowserWindow *window = nullptr, QObject *parent = nullptr);
     int id() const;
     bool incognito() const;
     QString title() const;
diff --git a/src/lib/plugins/qml/api/windows/qmlwindows.cpp b/src/lib/plugins/qml/api/windows/qmlwindows.cpp
index 6b79cfd87..88ac6d94c 100644
--- a/src/lib/plugins/qml/api/windows/qmlwindows.cpp
+++ b/src/lib/plugins/qml/api/windows/qmlwindows.cpp
@@ -42,7 +42,7 @@ QmlWindow *QmlWindows::get(const QVariantMap &map) const
         return nullptr;
     }
 
-    int id = map.value(QSL("id")).toInt();
+    const int id = map.value(QSL("id")).toInt();
     return windowData->get(getBrowserWindow(id));
 }
 
@@ -62,8 +62,8 @@ QList<QObject*> QmlWindows::getAll() const
 
 QmlWindow *QmlWindows::create(const QVariantMap &map) const
 {
-    QUrl url = QUrl::fromEncoded(map.value(QSL("url")).toString().toUtf8());
-    Qz::BrowserWindowType type = Qz::BrowserWindowType(map.value(QSL("type"), QmlWindowType::NewWindow).toInt());
+    const QUrl url = QUrl::fromEncoded(map.value(QSL("url")).toString().toUtf8());
+    const Qz::BrowserWindowType type = Qz::BrowserWindowType(map.value(QSL("type"), QmlWindowType::NewWindow).toInt());
     BrowserWindow *window = mApp->createWindow(type, url);
     return windowData->get(window);
 }
diff --git a/src/lib/plugins/qml/api/windows/qmlwindows.h b/src/lib/plugins/qml/api/windows/qmlwindows.h
index be0b8d218..b1de338f4 100644
--- a/src/lib/plugins/qml/api/windows/qmlwindows.h
+++ b/src/lib/plugins/qml/api/windows/qmlwindows.h
@@ -24,7 +24,7 @@ class QmlWindows : public QObject
 {
     Q_OBJECT
 public:
-    QmlWindows(QObject *parent = 0);
+    QmlWindows(QObject *parent = nullptr);
     Q_INVOKABLE QmlWindow *get(const QVariantMap &map) const;
     Q_INVOKABLE QmlWindow *getCurrent() const;
     Q_INVOKABLE QList<QObject*> getAll() const;
diff --git a/src/lib/plugins/qml/api/windows/qmlwindowstate.h b/src/lib/plugins/qml/api/windows/qmlwindowstate.h
index cd41e14e3..8f675f197 100644
--- a/src/lib/plugins/qml/api/windows/qmlwindowstate.h
+++ b/src/lib/plugins/qml/api/windows/qmlwindowstate.h
@@ -32,5 +32,5 @@ public:
     };
     Q_ENUMS(WindowState)
 
-    QmlWindowState(QObject *parent = 0);
+    QmlWindowState(QObject *parent = nullptr);
 };
diff --git a/src/lib/plugins/qml/api/windows/qmlwindowtype.h b/src/lib/plugins/qml/api/windows/qmlwindowtype.h
index c3c6338c0..12bf128ea 100644
--- a/src/lib/plugins/qml/api/windows/qmlwindowtype.h
+++ b/src/lib/plugins/qml/api/windows/qmlwindowtype.h
@@ -32,5 +32,5 @@ public:
     };
     Q_ENUMS(WindowType)
 
-    QmlWindowType(QObject *parent = 0);
+    QmlWindowType(QObject *parent = nullptr);
 };