diff --git a/src/webui/www/private/scripts/client.js b/src/webui/www/private/scripts/client.js
index 6151b66d4..81eb60454 100644
--- a/src/webui/www/private/scripts/client.js
+++ b/src/webui/www/private/scripts/client.js
@@ -218,7 +218,7 @@ window.addEventListener("DOMContentLoaded", () => {
         });
 
         // start off hidden
-        $("searchTabColumn").addClass("invisible");
+        $("searchTabColumn").classList.add("invisible");
     };
 
     const buildRssTab = () => {
@@ -229,7 +229,7 @@ window.addEventListener("DOMContentLoaded", () => {
         });
 
         // start off hidden
-        $("rssTabColumn").addClass("invisible");
+        $("rssTabColumn").classList.add("invisible");
     };
 
     const buildLogTab = () => {
@@ -240,7 +240,7 @@ window.addEventListener("DOMContentLoaded", () => {
         });
 
         // start off hidden
-        $("logTabColumn").addClass("invisible");
+        $("logTabColumn").classList.add("invisible");
     };
 
     buildTransfersTab();
@@ -340,22 +340,22 @@ window.addEventListener("DOMContentLoaded", () => {
     let showTopToolbar = LocalPreferences.get("show_top_toolbar", "true") === "true";
     if (!showTopToolbar) {
         $("showTopToolbarLink").firstElementChild.style.opacity = "0";
-        $("mochaToolbar").addClass("invisible");
+        $("mochaToolbar").classList.add("invisible");
     }
 
     // Show Status Bar is enabled by default
     let showStatusBar = LocalPreferences.get("show_status_bar", "true") === "true";
     if (!showStatusBar) {
         $("showStatusBarLink").firstElementChild.style.opacity = "0";
-        $("desktopFooterWrapper").addClass("invisible");
+        $("desktopFooterWrapper").classList.add("invisible");
     }
 
     // Show Filters Sidebar is enabled by default
     let showFiltersSidebar = LocalPreferences.get("show_filters_sidebar", "true") === "true";
     if (!showFiltersSidebar) {
         $("showFiltersSidebarLink").firstElementChild.style.opacity = "0";
-        $("filtersColumn").addClass("invisible");
-        $("filtersColumn_handle").addClass("invisible");
+        $("filtersColumn").classList.add("invisible");
+        $("filtersColumn_handle").classList.add("invisible");
     }
 
     let speedInTitle = LocalPreferences.get("speed_in_browser_title_bar") === "true";
@@ -1062,12 +1062,12 @@ window.addEventListener("DOMContentLoaded", () => {
                 $("queueingMenuItems").removeClass("invisible");
             }
             else {
-                $("topQueuePosItem").addClass("invisible");
-                $("increaseQueuePosItem").addClass("invisible");
-                $("decreaseQueuePosItem").addClass("invisible");
-                $("bottomQueuePosItem").addClass("invisible");
-                $("queueingButtons").addClass("invisible");
-                $("queueingMenuItems").addClass("invisible");
+                $("topQueuePosItem").classList.add("invisible");
+                $("increaseQueuePosItem").classList.add("invisible");
+                $("decreaseQueuePosItem").classList.add("invisible");
+                $("bottomQueuePosItem").classList.add("invisible");
+                $("queueingButtons").classList.add("invisible");
+                $("queueingMenuItems").classList.add("invisible");
             }
         }
 
@@ -1127,7 +1127,7 @@ window.addEventListener("DOMContentLoaded", () => {
         }
         else {
             $("showTopToolbarLink").firstElementChild.style.opacity = "0";
-            $("mochaToolbar").addClass("invisible");
+            $("mochaToolbar").classList.add("invisible");
         }
         MochaUI.Desktop.setDesktopSize();
     });
@@ -1141,7 +1141,7 @@ window.addEventListener("DOMContentLoaded", () => {
         }
         else {
             $("showStatusBarLink").firstElementChild.style.opacity = "0";
-            $("desktopFooterWrapper").addClass("invisible");
+            $("desktopFooterWrapper").classList.add("invisible");
         }
         MochaUI.Desktop.setDesktopSize();
     });
@@ -1180,8 +1180,8 @@ window.addEventListener("DOMContentLoaded", () => {
         }
         else {
             $("showFiltersSidebarLink").firstElementChild.style.opacity = "0";
-            $("filtersColumn").addClass("invisible");
-            $("filtersColumn_handle").addClass("invisible");
+            $("filtersColumn").classList.add("invisible");
+            $("filtersColumn_handle").classList.add("invisible");
         }
         MochaUI.Desktop.setDesktopSize();
     });
@@ -1224,7 +1224,7 @@ window.addEventListener("DOMContentLoaded", () => {
         }
         else {
             $("showRssReaderLink").firstElementChild.style.opacity = "0";
-            $("rssTabLink").addClass("invisible");
+            $("rssTabLink").classList.add("invisible");
             if ($("rssTabLink").hasClass("selected"))
                 $("transfersTabLink").click();
         }
@@ -1238,7 +1238,7 @@ window.addEventListener("DOMContentLoaded", () => {
         }
         else {
             $("showSearchEngineLink").firstElementChild.style.opacity = "0";
-            $("searchTabLink").addClass("invisible");
+            $("searchTabLink").classList.add("invisible");
             if ($("searchTabLink").hasClass("selected"))
                 $("transfersTabLink").click();
         }
@@ -1252,14 +1252,14 @@ window.addEventListener("DOMContentLoaded", () => {
         }
         else {
             $("showLogViewerLink").firstElementChild.style.opacity = "0";
-            $("logTabLink").addClass("invisible");
+            $("logTabLink").classList.add("invisible");
             if ($("logTabLink").hasClass("selected"))
                 $("transfersTabLink").click();
         }
 
         // display no tabs
         if (!window.qBittorrent.Client.isShowRssReader() && !window.qBittorrent.Client.isShowSearchEngine() && !window.qBittorrent.Client.isShowLogViewer())
-            $("mainWindowTabs").addClass("invisible");
+            $("mainWindowTabs").classList.add("invisible");
     };
 
     $("StatisticsLink").addEventListener("click", () => { StatisticsLinkFN(); });
@@ -1286,10 +1286,10 @@ window.addEventListener("DOMContentLoaded", () => {
     };
 
     const hideTransfersTab = () => {
-        $("filtersColumn").addClass("invisible");
-        $("filtersColumn_handle").addClass("invisible");
-        $("mainColumn").addClass("invisible");
-        $("torrentsFilterToolbar").addClass("invisible");
+        $("filtersColumn").classList.add("invisible");
+        $("filtersColumn_handle").classList.add("invisible");
+        $("mainColumn").classList.add("invisible");
+        $("torrentsFilterToolbar").classList.add("invisible");
         MochaUI.Desktop.resizePanels();
     };
 
@@ -1323,7 +1323,7 @@ window.addEventListener("DOMContentLoaded", () => {
     })();
 
     const hideSearchTab = () => {
-        $("searchTabColumn").addClass("invisible");
+        $("searchTabColumn").classList.add("invisible");
         MochaUI.Desktop.resizePanels();
     };
 
@@ -1360,7 +1360,7 @@ window.addEventListener("DOMContentLoaded", () => {
     })();
 
     const hideRssTab = () => {
-        $("rssTabColumn").addClass("invisible");
+        $("rssTabColumn").classList.add("invisible");
         window.qBittorrent.Rss && window.qBittorrent.Rss.unload();
         MochaUI.Desktop.resizePanels();
     };
@@ -1398,7 +1398,7 @@ window.addEventListener("DOMContentLoaded", () => {
     })();
 
     const hideLogTab = () => {
-        $("logTabColumn").addClass("invisible");
+        $("logTabColumn").classList.add("invisible");
         MochaUI.Desktop.resizePanels();
         window.qBittorrent.Log && window.qBittorrent.Log.unload();
     };
diff --git a/src/webui/www/private/scripts/contextmenu.js b/src/webui/www/private/scripts/contextmenu.js
index 00ea280a4..26bb59f1a 100644
--- a/src/webui/www/private/scripts/contextmenu.js
+++ b/src/webui/www/private/scripts/contextmenu.js
@@ -257,7 +257,7 @@ window.qBittorrent.ContextMenu ??= (() => {
 
         // hide an item
         hideItem(item) {
-            this.menu.getElement("a[href$=" + item + "]").parentNode.addClass("invisible");
+            this.menu.getElement("a[href$=" + item + "]").parentNode.classList.add("invisible");
             return this;
         }
 
@@ -405,7 +405,7 @@ window.qBittorrent.ContextMenu ??= (() => {
 
             if (all_are_downloaded) {
                 this.hideItem("downloadLimit");
-                this.menu.getElement("a[href$=uploadLimit]").parentNode.addClass("separator");
+                this.menu.getElement("a[href$=uploadLimit]").parentNode.classList.add("separator");
                 this.hideItem("sequentialDownload");
                 this.hideItem("firstLastPiecePrio");
                 this.showItem("superSeeding");
@@ -416,7 +416,7 @@ window.qBittorrent.ContextMenu ??= (() => {
                 const show_f_l_piece_prio = (all_are_f_l_piece_prio || !there_are_f_l_piece_prio);
 
                 if (!show_seq_dl && show_f_l_piece_prio)
-                    this.menu.getElement("a[href$=firstLastPiecePrio]").parentNode.addClass("separator");
+                    this.menu.getElement("a[href$=firstLastPiecePrio]").parentNode.classList.add("separator");
                 else
                     this.menu.getElement("a[href$=firstLastPiecePrio]").parentNode.removeClass("separator");
 
@@ -525,7 +525,7 @@ window.qBittorrent.ContextMenu ??= (() => {
                 const setCategoryItem = document.createElement("li");
                 setCategoryItem.appendChild(anchor);
                 if (first) {
-                    setCategoryItem.addClass("separator");
+                    setCategoryItem.classList.add("separator");
                     first = false;
                 }
 
@@ -583,7 +583,7 @@ window.qBittorrent.ContextMenu ??= (() => {
                 const setTagItem = document.createElement("li");
                 setTagItem.appendChild(anchor);
                 if (i === 0)
-                    setTagItem.addClass("separator");
+                    setTagItem.classList.add("separator");
 
                 contextTagList.appendChild(setTagItem);
             }
@@ -661,7 +661,7 @@ window.qBittorrent.ContextMenu ??= (() => {
     class RssFeedContextMenu extends ContextMenu {
         updateMenuItems() {
             const selectedRows = window.qBittorrent.Rss.rssFeedTable.selectedRowsIds();
-            this.menu.getElement("a[href$=newSubscription]").parentNode.addClass("separator");
+            this.menu.getElement("a[href$=newSubscription]").parentNode.classList.add("separator");
             switch (selectedRows.length) {
                 case 0:
                     // remove separator on top of newSubscription entry to avoid double line
diff --git a/src/webui/www/private/scripts/dynamicTable.js b/src/webui/www/private/scripts/dynamicTable.js
index 5e6017f02..0074bbf8c 100644
--- a/src/webui/www/private/scripts/dynamicTable.js
+++ b/src/webui/www/private/scripts/dynamicTable.js
@@ -597,9 +597,9 @@ window.qBittorrent.DynamicTable ??= (() => {
                 th.textContent = this.columns[i].caption;
                 th.setAttribute("style", "width: " + this.columns[i].width + "px;" + this.columns[i].style);
                 th.columnName = this.columns[i].name;
-                th.addClass("column_" + th.columnName);
+                th.classList.add("column_" + th.columnName);
                 if ((this.columns[i].visible === "0") || this.columns[i].force_hide)
-                    th.addClass("invisible");
+                    th.classList.add("invisible");
                 else
                     th.removeClass("invisible");
             }
@@ -631,10 +631,10 @@ window.qBittorrent.DynamicTable ??= (() => {
                     trs[i].getElements("td")[pos].removeClass("invisible");
             }
             else {
-                ths[pos].addClass("invisible");
-                fths[pos].addClass("invisible");
+                ths[pos].classList.add("invisible");
+                fths[pos].classList.add("invisible");
                 for (let j = 0; j < trs.length; ++j)
-                    trs[j].getElements("td")[pos].addClass("invisible");
+                    trs[j].getElements("td")[pos].classList.add("invisible");
             }
             if (this.columns[pos].onResize !== null)
                 this.columns[pos].onResize(columnName);
@@ -675,9 +675,9 @@ window.qBittorrent.DynamicTable ??= (() => {
 
             const colElem = getCol(this.dynamicTableFixedHeaderDivId, newColumn);
             if (colElem !== null) {
-                colElem.addClass("sorted");
+                colElem.classList.add("sorted");
                 if (isReverse)
-                    colElem.addClass("reverse");
+                    colElem.classList.add("reverse");
                 else
                     colElem.removeClass("reverse");
             }
@@ -712,7 +712,7 @@ window.qBittorrent.DynamicTable ??= (() => {
                 const tr = trs[i];
                 this.selectedRows.push(tr.rowId);
                 if (!tr.hasClass("selected"))
-                    tr.addClass("selected");
+                    tr.classList.add("selected");
             }
         },
 
@@ -759,7 +759,7 @@ window.qBittorrent.DynamicTable ??= (() => {
             this.selectedRows = rowIds.slice();
             this.tableBody.getElements("tr").each((tr) => {
                 if (rowIds.includes(tr.rowId))
-                    tr.addClass("selected");
+                    tr.classList.add("selected");
             });
         },
 
@@ -767,7 +767,7 @@ window.qBittorrent.DynamicTable ??= (() => {
             const that = this;
             this.tableBody.getElements("tr").each((tr) => {
                 if (that.isRowSelected(tr.rowId))
-                    tr.addClass("selected");
+                    tr.classList.add("selected");
                 else
                     tr.removeClass("selected");
             });
@@ -874,7 +874,7 @@ window.qBittorrent.DynamicTable ??= (() => {
                     for (let k = 0; k < this.columns.length; ++k) {
                         const td = new Element("td");
                         if ((this.columns[k].visible === "0") || this.columns[k].force_hide)
-                            td.addClass("invisible");
+                            td.classList.add("invisible");
                         td.injectInside(tr);
                     }
 
@@ -1959,13 +1959,13 @@ window.qBittorrent.DynamicTable ??= (() => {
                 if (value) {
                     td.textContent = "QBT_TR(Yes)QBT_TR[CONTEXT=SearchPluginsTable]";
                     td.title = "QBT_TR(Yes)QBT_TR[CONTEXT=SearchPluginsTable]";
-                    td.getParent("tr").addClass("green");
+                    td.getParent("tr").classList.add("green");
                     td.getParent("tr").removeClass("red");
                 }
                 else {
                     td.textContent = "QBT_TR(No)QBT_TR[CONTEXT=SearchPluginsTable]";
                     td.title = "QBT_TR(No)QBT_TR[CONTEXT=SearchPluginsTable]";
-                    td.getParent("tr").addClass("red");
+                    td.getParent("tr").classList.add("red");
                     td.getParent("tr").removeClass("green");
                 }
             };
@@ -2988,7 +2988,7 @@ window.qBittorrent.DynamicTable ??= (() => {
             const row = this.rows.get(tr.rowId);
             const data = row[fullUpdate ? "full_data" : "data"];
             if (!row.full_data.isRead)
-                tr.addClass("unreadArticle");
+                tr.classList.add("unreadArticle");
             else
                 tr.removeClass("unreadArticle");
 
@@ -3260,12 +3260,12 @@ window.qBittorrent.DynamicTable ??= (() => {
             const data = row[fullUpdate ? "full_data" : "data"];
 
             if (row.full_data.isFeed) {
-                tr.addClass("articleTableFeed");
+                tr.classList.add("articleTableFeed");
                 tr.removeClass("articleTableArticle");
             }
             else {
                 tr.removeClass("articleTableFeed");
-                tr.addClass("articleTableArticle");
+                tr.classList.add("articleTableArticle");
             }
 
             const tds = tr.getElements("td");
diff --git a/src/webui/www/private/scripts/prop-files.js b/src/webui/www/private/scripts/prop-files.js
index 2fbc3a962..0bf253bb0 100644
--- a/src/webui/www/private/scripts/prop-files.js
+++ b/src/webui/www/private/scripts/prop-files.js
@@ -179,7 +179,7 @@ window.qBittorrent.PropFiles ??= (() => {
         select.id = "comboPrio" + id;
         select.setAttribute("data-id", id);
         select.setAttribute("data-file-id", fileId);
-        select.addClass("combo_priority");
+        select.classList.add("combo_priority");
         select.addEventListener("change", fileComboboxChanged);
 
         select.appendChild(createOption(FilePriority.Ignored, (FilePriority.Ignored === selectedPriority), "QBT_TR(Do not download)QBT_TR[CONTEXT=PropListDelegate]"));
@@ -669,7 +669,7 @@ window.qBittorrent.PropFiles ??= (() => {
             return;
         const rowElem = span.parentElement.parentElement;
         if (shouldHide)
-            rowElem.addClass("invisible");
+            rowElem.classList.add("invisible");
         else
             rowElem.removeClass("invisible");
     };
@@ -690,7 +690,7 @@ window.qBittorrent.PropFiles ??= (() => {
         // rotate the collapse icon
         const collapseIcon = td.getElementsByClassName("filesTableCollapseIcon")[0];
         if (isCollapsed)
-            collapseIcon.addClass("rotate");
+            collapseIcon.classList.add("rotate");
         else
             collapseIcon.removeClass("rotate");
     };
diff --git a/src/webui/www/private/views/aboutToolbar.html b/src/webui/www/private/views/aboutToolbar.html
index 21f25080d..b7275b662 100644
--- a/src/webui/www/private/views/aboutToolbar.html
+++ b/src/webui/www/private/views/aboutToolbar.html
@@ -17,32 +17,32 @@
         MochaUI.initializeTabs("aboutTabs");
 
         $("aboutAboutLink").addEventListener("click", () => {
-            $$(".aboutTabContent").addClass("invisible");
+            $$(".aboutTabContent").forEach(tab => { tab.classList.add("invisible"); });
             $("aboutAboutContent").removeClass("invisible");
         });
 
         $("aboutAuthorLink").addEventListener("click", () => {
-            $$(".aboutTabContent").addClass("invisible");
+            $$(".aboutTabContent").forEach(tab => { tab.classList.add("invisible"); });
             $("aboutAuthorContent").removeClass("invisible");
         });
 
         $("aboutSpecialThanksLink").addEventListener("click", () => {
-            $$(".aboutTabContent").addClass("invisible");
+            $$(".aboutTabContent").forEach(tab => { tab.classList.add("invisible"); });
             $("aboutSpecialThanksContent").removeClass("invisible");
         });
 
         $("aboutTranslatorsLink").addEventListener("click", () => {
-            $$(".aboutTabContent").addClass("invisible");
+            $$(".aboutTabContent").forEach(tab => { tab.classList.add("invisible"); });
             $("aboutTranslatorsContent").removeClass("invisible");
         });
 
         $("aboutLicenseLink").addEventListener("click", () => {
-            $$(".aboutTabContent").addClass("invisible");
+            $$(".aboutTabContent").forEach(tab => { tab.classList.add("invisible"); });
             $("aboutLicenseContent").removeClass("invisible");
         });
 
         $("aboutSoftwareUsedLink").addEventListener("click", () => {
-            $$(".aboutTabContent").addClass("invisible");
+            $$(".aboutTabContent").forEach(tab => { tab.classList.add("invisible"); });
             $("aboutSoftwareUsedContent").removeClass("invisible");
         });
     })();
diff --git a/src/webui/www/private/views/log.html b/src/webui/www/private/views/log.html
index eab8c2134..26d76d162 100644
--- a/src/webui/www/private/views/log.html
+++ b/src/webui/www/private/views/log.html
@@ -307,12 +307,12 @@
             if (currentSelectedTab === "main") {
                 selectBox.enable();
                 $("logMessageView").removeClass("invisible");
-                $("logPeerView").addClass("invisible");
+                $("logPeerView").classList.add("invisible");
                 resetTableTimer("peer");
             }
             else {
                 selectBox.disable();
-                $("logMessageView").addClass("invisible");
+                $("logMessageView").classList.add("invisible");
                 $("logPeerView").removeClass("invisible");
                 resetTableTimer("main");
             }
diff --git a/src/webui/www/private/views/preferencesToolbar.html b/src/webui/www/private/views/preferencesToolbar.html
index ee7eee500..d96b485ee 100644
--- a/src/webui/www/private/views/preferencesToolbar.html
+++ b/src/webui/www/private/views/preferencesToolbar.html
@@ -37,35 +37,35 @@
         MochaUI.initializeTabs("preferencesTabs");
 
         $("PrefBehaviorLink").addEventListener("click", (e) => {
-            $$(".PrefTab").addClass("invisible");
+            $$(".PrefTab").forEach(tab => { tab.classList.add("invisible"); });
             $("BehaviorTab").removeClass("invisible");
         });
         $("PrefDownloadsLink").addEventListener("click", (e) => {
-            $$(".PrefTab").addClass("invisible");
+            $$(".PrefTab").forEach(tab => { tab.classList.add("invisible"); });
             $("DownloadsTab").removeClass("invisible");
         });
         $("PrefConnectionLink").addEventListener("click", (e) => {
-            $$(".PrefTab").addClass("invisible");
+            $$(".PrefTab").forEach(tab => { tab.classList.add("invisible"); });
             $("ConnectionTab").removeClass("invisible");
         });
         $("PrefSpeedLink").addEventListener("click", (e) => {
-            $$(".PrefTab").addClass("invisible");
+            $$(".PrefTab").forEach(tab => { tab.classList.add("invisible"); });
             $("SpeedTab").removeClass("invisible");
         });
         $("PrefBittorrentLink").addEventListener("click", (e) => {
-            $$(".PrefTab").addClass("invisible");
+            $$(".PrefTab").forEach(tab => { tab.classList.add("invisible"); });
             $("BittorrentTab").removeClass("invisible");
         });
         $("PrefRSSLink").addEventListener("click", (e) => {
-            $$(".PrefTab").addClass("invisible");
+            $$(".PrefTab").forEach(tab => { tab.classList.add("invisible"); });
             $("RSSTab").removeClass("invisible");
         });
         $("PrefWebUILink").addEventListener("click", (e) => {
-            $$(".PrefTab").addClass("invisible");
+            $$(".PrefTab").forEach(tab => { tab.classList.add("invisible"); });
             $("WebUITab").removeClass("invisible");
         });
         $("PrefAdvancedLink").addEventListener("click", (e) => {
-            $$(".PrefTab").addClass("invisible");
+            $$(".PrefTab").forEach(tab => { tab.classList.add("invisible"); });
             $("AdvancedTab").removeClass("invisible");
         });
     })();