diff --git a/src/webui/api/appcontroller.cpp b/src/webui/api/appcontroller.cpp
index 89b21217b..9c9404cbb 100644
--- a/src/webui/api/appcontroller.cpp
+++ b/src/webui/api/appcontroller.cpp
@@ -95,7 +95,7 @@ void AppController::preferencesAction()
 {
     const Preferences *const pref = Preferences::instance();
     const auto *session = BitTorrent::Session::instance();
-    QVariantHash data;
+    QJsonObject data;
 
     // Downloads
     // When adding a torrent
@@ -116,7 +116,7 @@ void AppController::preferencesAction()
     data["export_dir_fin"] = Utils::Fs::toNativePath(session->finishedTorrentExportDirectory());
     // Automatically add torrents from
     const QVariantHash dirs = pref->getScanDirs();
-    QVariantHash nativeDirs;
+    QJsonObject nativeDirs;
     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());
@@ -248,7 +248,7 @@ void AppController::preferencesAction()
     data["dyndns_domain"] = pref->getDynDomainName();
 
     // RSS settings
-    data["rss_refresh_interval"] = RSS::Session::instance()->refreshInterval();
+    data["rss_refresh_interval"] = static_cast<double>(RSS::Session::instance()->refreshInterval());
     data["rss_max_articles_per_feed"] = RSS::Session::instance()->maxArticlesPerFeed();
     data["rss_processing_enabled"] = RSS::Session::instance()->isProcessingEnabled();
     data["rss_auto_downloading_enabled"] = RSS::AutoDownloader::instance()->isProcessingEnabled();
@@ -262,7 +262,7 @@ void AppController::preferencesAction()
     // Listen on IPv6 address
     data["listen_on_ipv6_address"] = session->isIPv6Enabled();
     // Save resume data interval
-    data["save_resume_data_interval"] = session->saveResumeDataInterval();
+    data["save_resume_data_interval"] = static_cast<double>(session->saveResumeDataInterval());
     // Recheck completed torrents
     data["recheck_completed_torrents"] = pref->recheckTorrentsOnCompletion();
     // Resolve peer countries
@@ -311,7 +311,7 @@ void AppController::preferencesAction()
     data["announce_to_all_tiers"] = session->announceToAllTiers();
     data["announce_ip"] = session->announceIP();
 
-    setResult(QJsonObject::fromVariantHash(data));
+    setResult(data);
 }
 
 void AppController::setPreferencesAction()
@@ -747,17 +747,17 @@ void AppController::defaultSavePathAction()
 
 void AppController::networkInterfaceListAction()
 {
-    QVariantList ifaceList;
+    QJsonArray ifaceList;
     for (const QNetworkInterface &iface : asConst(QNetworkInterface::allInterfaces())) {
         if (!iface.addressEntries().isEmpty()) {
-            ifaceList.append(QVariantHash {
+            ifaceList.append(QJsonObject {
                 {"name", iface.humanReadableName()},
                 {"value", iface.name()}
             });
         }
     }
 
-    setResult(QJsonArray::fromVariantList(ifaceList));
+    setResult(ifaceList);
 }
 
 void AppController::networkInterfaceAddressListAction()
@@ -765,7 +765,7 @@ void AppController::networkInterfaceAddressListAction()
     checkParams({"iface"});
 
     const QString ifaceName = params().value("iface");
-    QVariantList addressList;
+    QJsonArray addressList;
 
     if (ifaceName.isEmpty()) {
         for (const QHostAddress &ip : asConst(QNetworkInterface::allAddresses()))
@@ -777,5 +777,5 @@ void AppController::networkInterfaceAddressListAction()
             addressList.append(entry.ip().toString());
     }
 
-    setResult(QJsonArray::fromVariantList(addressList));
+    setResult(addressList);
 }
diff --git a/src/webui/api/logcontroller.cpp b/src/webui/api/logcontroller.cpp
index 9637e788c..2ef0c3e3c 100644
--- a/src/webui/api/logcontroller.cpp
+++ b/src/webui/api/logcontroller.cpp
@@ -29,6 +29,7 @@
 #include "logcontroller.h"
 
 #include <QJsonArray>
+#include <QJsonObject>
 
 #include "base/global.h"
 #include "base/logger.h"
@@ -70,7 +71,7 @@ void LogController::mainAction()
         lastKnownId = -1;
 
     Logger *const logger = Logger::instance();
-    QVariantList msgList;
+    QJsonArray msgList;
 
     for (const Log::Msg &msg : asConst(logger->getMessages(lastKnownId))) {
         if (!((msg.type == Log::NORMAL && isNormal)
@@ -79,7 +80,7 @@ void LogController::mainAction()
               || (msg.type == Log::CRITICAL && isCritical)))
             continue;
 
-        msgList.append(QVariantHash {
+        msgList.append(QJsonObject {
             {KEY_LOG_ID, msg.id},
             {KEY_LOG_TIMESTAMP, msg.timestamp},
             {KEY_LOG_MSG_TYPE, msg.type},
@@ -87,7 +88,7 @@ void LogController::mainAction()
         });
     }
 
-    setResult(QJsonArray::fromVariantList(msgList));
+    setResult(msgList);
 }
 
 // Returns the peer log in JSON format.
@@ -110,10 +111,10 @@ void LogController::peersAction()
         lastKnownId = -1;
 
     Logger *const logger = Logger::instance();
-    QVariantList peerList;
+    QJsonArray peerList;
 
     for (const Log::Peer &peer : asConst(logger->getPeers(lastKnownId))) {
-        peerList.append(QVariantHash {
+        peerList.append(QJsonObject {
             {KEY_LOG_ID, peer.id},
             {KEY_LOG_TIMESTAMP, peer.timestamp},
             {KEY_LOG_PEER_IP, peer.ip},
@@ -122,5 +123,5 @@ void LogController::peersAction()
         });
     }
 
-    setResult(QJsonArray::fromVariantList(peerList));
+    setResult(peerList);
 }
diff --git a/src/webui/api/torrentscontroller.cpp b/src/webui/api/torrentscontroller.cpp
index bb4ec9ea4..575cb9acc 100644
--- a/src/webui/api/torrentscontroller.cpp
+++ b/src/webui/api/torrentscontroller.cpp
@@ -131,9 +131,9 @@ namespace
         }
     }
 
-    QVariantList getStickyTrackers(const BitTorrent::TorrentHandle *const torrent)
+    QJsonArray getStickyTrackers(const BitTorrent::TorrentHandle *const torrent)
     {
-        uint seedsDHT = 0, seedsPeX = 0, seedsLSD = 0, leechesDHT = 0, leechesPeX = 0, leechesLSD = 0;
+        int seedsDHT = 0, seedsPeX = 0, seedsLSD = 0, leechesDHT = 0, leechesPeX = 0, leechesLSD = 0;
         for (const BitTorrent::PeerInfo &peer : asConst(torrent->peers())) {
             if (peer.isConnecting()) continue;
 
@@ -161,7 +161,7 @@ namespace
         const QString privateMsg {QCoreApplication::translate("TrackerListWidget", "This torrent is private")};
         const bool isTorrentPrivate = torrent->isPrivate();
 
-        const QVariantHash dht {
+        const QJsonObject dht {
             {KEY_TRACKER_URL, "** [DHT] **"},
             {KEY_TRACKER_TIER, ""},
             {KEY_TRACKER_MSG, (isTorrentPrivate ? privateMsg : "")},
@@ -172,7 +172,7 @@ namespace
             {KEY_TRACKER_LEECHES_COUNT, leechesDHT}
         };
 
-        const QVariantHash pex {
+        const QJsonObject pex {
             {KEY_TRACKER_URL, "** [PeX] **"},
             {KEY_TRACKER_TIER, ""},
             {KEY_TRACKER_MSG, (isTorrentPrivate ? privateMsg : "")},
@@ -183,7 +183,7 @@ namespace
             {KEY_TRACKER_LEECHES_COUNT, leechesPeX}
         };
 
-        const QVariantHash lsd {
+        const QJsonObject lsd {
             {KEY_TRACKER_URL, "** [LSD] **"},
             {KEY_TRACKER_TIER, ""},
             {KEY_TRACKER_MSG, (isTorrentPrivate ? privateMsg : "")},
@@ -194,7 +194,7 @@ namespace
             {KEY_TRACKER_LEECHES_COUNT, leechesLSD}
         };
 
-        return QVariantList {dht, pex, lsd};
+        return {dht, pex, lsd};
     }
 }
 
@@ -309,14 +309,14 @@ void TorrentsController::propertiesAction()
     checkParams({"hash"});
 
     const QString hash {params()["hash"]};
-    QVariantHash dataDict;
+    QJsonObject dataDict;
     BitTorrent::TorrentHandle *const torrent = BitTorrent::Session::instance()->findTorrent(hash);
     if (!torrent)
         throw APIError(APIErrorType::NotFound);
 
     dataDict[KEY_PROP_TIME_ELAPSED] = torrent->activeTime();
     dataDict[KEY_PROP_SEEDING_TIME] = torrent->seedingTime();
-    dataDict[KEY_PROP_ETA] = torrent->eta();
+    dataDict[KEY_PROP_ETA] = static_cast<double>(torrent->eta());
     dataDict[KEY_PROP_CONNECT_COUNT] = torrent->connectionsCount();
     dataDict[KEY_PROP_CONNECT_COUNT_LIMIT] = torrent->connectionsLimit();
     dataDict[KEY_PROP_DOWNLOADED] = torrent->totalDownload();
@@ -344,11 +344,11 @@ void TorrentsController::propertiesAction()
     dataDict[KEY_PROP_PIECE_SIZE] = torrent->pieceLength();
     dataDict[KEY_PROP_PIECES_HAVE] = torrent->piecesHave();
     dataDict[KEY_PROP_CREATED_BY] = torrent->creator();
-    dataDict[KEY_PROP_ADDITION_DATE] = torrent->addedTime().toTime_t();
+    dataDict[KEY_PROP_ADDITION_DATE] = static_cast<double>(torrent->addedTime().toSecsSinceEpoch());
     if (torrent->hasMetadata()) {
         dataDict[KEY_PROP_LAST_SEEN] = torrent->lastSeenComplete().isValid() ? static_cast<int>(torrent->lastSeenComplete().toTime_t()) : -1;
         dataDict[KEY_PROP_COMPLETION_DATE] = torrent->completedTime().isValid() ? static_cast<int>(torrent->completedTime().toTime_t()) : -1;
-        dataDict[KEY_PROP_CREATION_DATE] = torrent->creationDate().toTime_t();
+        dataDict[KEY_PROP_CREATION_DATE] = static_cast<double>(torrent->creationDate().toSecsSinceEpoch());
     }
     else {
         dataDict[KEY_PROP_LAST_SEEN] = -1;
@@ -358,7 +358,7 @@ void TorrentsController::propertiesAction()
     dataDict[KEY_PROP_SAVE_PATH] = Utils::Fs::toNativePath(torrent->savePath());
     dataDict[KEY_PROP_COMMENT] = torrent->comment();
 
-    setResult(QJsonObject::fromVariantHash(dataDict));
+    setResult(dataDict);
 }
 
 // Returns the trackers for a torrent in JSON format.
@@ -381,13 +381,13 @@ void TorrentsController::trackersAction()
     if (!torrent)
         throw APIError(APIErrorType::NotFound);
 
-    QVariantList trackerList = getStickyTrackers(torrent);
+    QJsonArray trackerList = getStickyTrackers(torrent);
 
     QHash<QString, BitTorrent::TrackerInfo> trackersData = torrent->trackerInfos();
     for (const BitTorrent::TrackerEntry &tracker : asConst(torrent->trackers())) {
         const BitTorrent::TrackerInfo data = trackersData.value(tracker.url());
 
-        trackerList << QVariantHash {
+        trackerList << QJsonObject {
             {KEY_TRACKER_URL, tracker.url()},
             {KEY_TRACKER_TIER, tracker.tier()},
             {KEY_TRACKER_STATUS, static_cast<int>(tracker.status())},
@@ -399,7 +399,7 @@ void TorrentsController::trackersAction()
         };
     }
 
-    setResult(QJsonArray::fromVariantList(trackerList));
+    setResult(trackerList);
 }
 
 // Returns the web seeds for a torrent in JSON format.
@@ -411,18 +411,18 @@ void TorrentsController::webseedsAction()
     checkParams({"hash"});
 
     const QString hash {params()["hash"]};
-    QVariantList webSeedList;
+    QJsonArray webSeedList;
     BitTorrent::TorrentHandle *const torrent = BitTorrent::Session::instance()->findTorrent(hash);
     if (!torrent)
         throw APIError(APIErrorType::NotFound);
 
     for (const QUrl &webseed : asConst(torrent->urlSeeds())) {
-        webSeedList.append(QVariantHash {
+        webSeedList.append(QJsonObject {
             {KEY_WEBSEED_URL, webseed.toString()}
         });
     }
 
-    setResult(QJsonArray::fromVariantList(webSeedList));
+    setResult(webSeedList);
 }
 
 // Returns the files in a torrent in JSON format.
@@ -440,7 +440,7 @@ void TorrentsController::filesAction()
     checkParams({"hash"});
 
     const QString hash {params()["hash"]};
-    QVariantList fileList;
+    QJsonArray fileList;
     const BitTorrent::TorrentHandle *const torrent = BitTorrent::Session::instance()->findTorrent(hash);
     if (!torrent)
         throw APIError(APIErrorType::NotFound);
@@ -451,7 +451,7 @@ void TorrentsController::filesAction()
         const QVector<qreal> fileAvailability = torrent->availableFileFractions();
         const BitTorrent::TorrentInfo info = torrent->info();
         for (int i = 0; i < torrent->filesCount(); ++i) {
-            QVariantHash fileDict = {
+            QJsonObject fileDict = {
                 {KEY_FILE_PROGRESS, fp[i]},
                 {KEY_FILE_PRIORITY, static_cast<int>(priorities[i])},
                 {KEY_FILE_SIZE, torrent->fileSize(i)},
@@ -464,7 +464,7 @@ void TorrentsController::filesAction()
             fileDict[KEY_FILE_NAME] = Utils::Fs::toNativePath(fileName);
 
             const BitTorrent::TorrentInfo::PieceRange idx = info.filePieces(i);
-            fileDict[KEY_FILE_PIECE_RANGE] = QVariantList {idx.first(), idx.last()};
+            fileDict[KEY_FILE_PIECE_RANGE] = QJsonArray {idx.first(), idx.last()};
 
             if (i == 0)
                 fileDict[KEY_FILE_IS_SEED] = torrent->isSeed();
@@ -473,7 +473,7 @@ void TorrentsController::filesAction()
         }
     }
 
-    setResult(QJsonArray::fromVariantList(fileList));
+    setResult(fileList);
 }
 
 // Returns an array of hashes (of each pieces respectively) for a torrent in JSON format.
@@ -483,17 +483,16 @@ void TorrentsController::pieceHashesAction()
     checkParams({"hash"});
 
     const QString hash {params()["hash"]};
-    QVariantList pieceHashes;
+    QJsonArray pieceHashes;
     BitTorrent::TorrentHandle *const torrent = BitTorrent::Session::instance()->findTorrent(hash);
     if (!torrent)
         throw APIError(APIErrorType::NotFound);
 
     const QVector<QByteArray> hashes = torrent->info().pieceHashes();
-    pieceHashes.reserve(hashes.size());
     for (const QByteArray &hash : hashes)
-        pieceHashes.append(hash.toHex());
+        pieceHashes.append(QString(hash.toHex()));
 
-    setResult(QJsonArray::fromVariantList(pieceHashes));
+    setResult(pieceHashes);
 }
 
 // Returns an array of states (of each pieces respectively) for a torrent in JSON format.
@@ -506,13 +505,12 @@ void TorrentsController::pieceStatesAction()
     checkParams({"hash"});
 
     const QString hash {params()["hash"]};
-    QVariantList pieceStates;
+    QJsonArray pieceStates;
     BitTorrent::TorrentHandle *const torrent = BitTorrent::Session::instance()->findTorrent(hash);
     if (!torrent)
         throw APIError(APIErrorType::NotFound);
 
     const QBitArray states = torrent->pieces();
-    pieceStates.reserve(states.size());
     for (int i = 0; i < states.size(); ++i)
         pieceStates.append(static_cast<int>(states[i]) * 2);
 
@@ -522,7 +520,7 @@ void TorrentsController::pieceStatesAction()
             pieceStates[i] = 1;
     }
 
-    setResult(QJsonArray::fromVariantList(pieceStates));
+    setResult(pieceStates);
 }
 
 void TorrentsController::addAction()
@@ -743,7 +741,7 @@ void TorrentsController::uploadLimitAction()
     checkParams({"hashes"});
 
     const QStringList hashes {params()["hashes"].split('|')};
-    QVariantHash map;
+    QJsonObject map;
     for (const QString &hash : hashes) {
         int limit = -1;
         const BitTorrent::TorrentHandle *const torrent = BitTorrent::Session::instance()->findTorrent(hash);
@@ -752,7 +750,7 @@ void TorrentsController::uploadLimitAction()
         map[hash] = limit;
     }
 
-    setResult(QJsonObject::fromVariantHash(map));
+    setResult(map);
 }
 
 void TorrentsController::downloadLimitAction()
@@ -760,7 +758,7 @@ void TorrentsController::downloadLimitAction()
     checkParams({"hashes"});
 
     const QStringList hashes {params()["hashes"].split('|')};
-    QVariantHash map;
+    QJsonObject map;
     for (const QString &hash : hashes) {
         int limit = -1;
         const BitTorrent::TorrentHandle *const torrent = BitTorrent::Session::instance()->findTorrent(hash);
@@ -769,7 +767,7 @@ void TorrentsController::downloadLimitAction()
         map[hash] = limit;
     }
 
-    setResult(QJsonObject::fromVariantHash(map));
+    setResult(map);
 }
 
 void TorrentsController::setUploadLimitAction()
@@ -1103,6 +1101,8 @@ void TorrentsController::deleteTagsAction()
 
 void TorrentsController::tagsAction()
 {
-    const QStringList tags = BitTorrent::Session::instance()->tags().toList();
-    setResult(QJsonArray::fromStringList(tags));
+    QJsonArray result;
+    for (const QString &tag : asConst(BitTorrent::Session::instance()->tags()))
+        result << tag;
+    setResult(result);
 }