diff --git a/src/api-wrappers/AXUIElement.swift b/src/api-wrappers/AXUIElement.swift
index 265c9387..2c9d73c8 100644
--- a/src/api-wrappers/AXUIElement.swift
+++ b/src/api-wrappers/AXUIElement.swift
@@ -43,9 +43,12 @@ extension AXUIElement {
         return attribute(kAXTitleAttribute, String.self)
     }
 
-    func windows(_ bundleIdentifier: String?) -> [AXUIElement]? {
-        return attribute(kAXWindowsAttribute, [AXUIElement].self)?
-            .filter { $0.isActualWindow(bundleIdentifier) }
+    func windows() -> [AXUIElement]? {
+        return attribute(kAXWindowsAttribute, [AXUIElement].self)
+    }
+
+    func isTabbed(_ window: AXUIElement) -> Bool {
+        return windows()?.first(where: { $0 == window }) == nil
     }
 
     func isMinimized() -> Bool {
diff --git a/src/logic/Application.swift b/src/logic/Application.swift
index f78a6fbe..755820e6 100644
--- a/src/logic/Application.swift
+++ b/src/logic/Application.swift
@@ -12,6 +12,7 @@ class Application: NSObject {
         kAXWindowCreatedNotification,
         kAXApplicationHiddenNotification,
         kAXApplicationShownNotification,
+        kAXFocusedUIElementChangedNotification,
     ]
 
     // some apps never finish their subscription retry loop; they should be stopped to avoid infinite loop
@@ -51,7 +52,8 @@ class Application: NSObject {
     }
 
     func observeNewWindows() {
-        if let windows = axUiElement!.windows(runningApplication.bundleIdentifier) {
+        if let windows = (axUiElement!.windows()?
+            .filter { $0.isActualWindow(runningApplication.bundleIdentifier) }) {
             let actualWindows = windows.filter { Windows.list.firstIndexThatMatches($0) == nil }
             if actualWindows.count > 0 {
                 addWindows(actualWindows)
diff --git a/src/logic/Window.swift b/src/logic/Window.swift
index b8ea8b63..0c5d1101 100644
--- a/src/logic/Window.swift
+++ b/src/logic/Window.swift
@@ -6,6 +6,7 @@ class Window {
     var thumbnail: NSImage?
     var icon: NSImage?
     var shouldShowTheUser = true
+    var isTabbed: Bool
     var isHidden: Bool
     var isMinimized: Bool
     var isOnAllSpaces: Bool
@@ -36,6 +37,7 @@ class Window {
         self.application = application
         self.cgWindowId = axUiElement.cgWindowId()
         self.icon = application.runningApplication.icon
+        self.isTabbed = application.axUiElement!.isTabbed(axUiElement)
         self.isHidden = application.runningApplication.isHidden
         self.isMinimized = axUiElement.isMinimized()
         self.spaceId = Spaces.currentSpaceId
diff --git a/src/logic/Windows.swift b/src/logic/Windows.swift
index 34ca11fe..0cef7a68 100644
--- a/src/logic/Windows.swift
+++ b/src/logic/Windows.swift
@@ -51,6 +51,8 @@ class Windows {
     }
 
     static func updatesWindowSpace(_ window: Window) {
+        // macOS bug: if you tab a window, then move the tab group to another space, other tabs from the tab group will stay on the current space
+        // you can use the Dock to focus one of the other tabs and it will teleport that tab in the current space, proving that it's a macOS bug
         let spaceIds = window.cgWindowId.spaces()
         if spaceIds.count == 1 {
             window.spaceId = spaceIds.first!
@@ -104,13 +106,7 @@ class Windows {
             !(Preferences.appsToShow == .active && window.application.runningApplication != NSWorkspace.shared.frontmostApplication) &&
             !(Preferences.spacesToShow == .active && window.spaceId != Spaces.currentSpaceId) &&
             !(Preferences.screensToShow == .showingAltTab && !isOnScreen(window, screen)) &&
-            (Preferences.showTabsAsWindows || !isTabbed(window))
-    }
-
-    static func isTabbed(_ window: Window) -> Bool {
-        let app = window.application
-        let windows = app.axUiElement?.windows(app.runningApplication.bundleIdentifier)
-        return windows?.first(where: { $0 == window.axUiElement }) == nil
+            (Preferences.showTabsAsWindows || !window.isTabbed)
     }
 
     static func isOnScreen(_ window: Window, _ screen: NSScreen) -> Bool {
diff --git a/src/logic/events/AccessibilityEvents.swift b/src/logic/events/AccessibilityEvents.swift
index 28762e4d..650492ad 100644
--- a/src/logic/events/AccessibilityEvents.swift
+++ b/src/logic/events/AccessibilityEvents.swift
@@ -14,10 +14,22 @@ func axObserverCallback(observer: AXObserver, element: AXUIElement, notification
              kAXWindowDeminiaturizedNotification: windowMiniaturizedOrDeminiaturized(element, type)
         case kAXTitleChangedNotification: windowTitleChanged(element)
         case kAXWindowResizedNotification: windowResized(element)
+        case kAXFocusedUIElementChangedNotification: focusedUiElementChanged(element, applicationPointer)
         default: return
     }
 }
 
+private func focusedUiElementChanged(_ element: AXUIElement, _ applicationPointer: UnsafeMutableRawPointer?) {
+    // this event is the only opportunity we have to check if a window became a tab, or a tab became a window
+    // we can only detect tabs for windows on the current space, as AXUIElement.windows() only reports current space windows
+    let application = Unmanaged<Application>.fromOpaque(applicationPointer!).takeUnretainedValue()
+    Windows.list.forEach {
+        if $0.spaceId == Spaces.currentSpaceId && $0.application == application {
+            $0.isTabbed = application.axUiElement!.isTabbed($0.axUiElement)
+        }
+    }
+}
+
 private func applicationActivated(_ element: AXUIElement) {
     guard let appFocusedWindow = element.focusedWindow(),
           let existingIndex = Windows.list.firstIndexThatMatches(appFocusedWindow) else { return }