diff --git a/src/qt/qt_mainwindow.cpp b/src/qt/qt_mainwindow.cpp
index 9ae180d1f..1c2e000ab 100644
--- a/src/qt/qt_mainwindow.cpp
+++ b/src/qt/qt_mainwindow.cpp
@@ -171,6 +171,8 @@ extern "C" void qt_blit(int x, int y, int w, int h, int monitor_index);
 
 extern MainWindow *main_window;
 
+bool MainWindow::s_adjustingForce43 = false;
+
 MainWindow::MainWindow(QWidget *parent)
     : QMainWindow(parent)
     , ui(new Ui::MainWindow)
@@ -1016,11 +1018,75 @@ void MainWindow::updateShortcuts()
 	ui->actionMute_Unmute->setShortcut(seq);
 }
 		
+void 
+MainWindow::adjustForForce43(const QSize &newWinSize)
+{
+    // Only act in resizable mode with Force 4:3 enabled and not fullscreen
+    if (!(vid_resize == 1 && force_43 > 0) || video_fullscreen || s_adjustingForce43)
+        return;
+
+    s_adjustingForce43 = true;
+
+    // Height consumed by menu/status/toolbars
+    int chromeH = menuBar()->height()
+                + (hide_status_bar ? 0 : statusBar()->height())
+                + (hide_tool_bar   ? 0 : ui->toolBar->height());
+
+    // Compute client area size in device‑independent pixels
+    double dpr = (!dpi_scale ? util::screenOfWidget(this)->devicePixelRatio() : 1.0);
+    int winW = newWinSize.width();
+    int winH = newWinSize.height();
+    int clientW = static_cast<int>(winW / dpr);
+    int clientH = static_cast<int>((winH - chromeH) / dpr);
+
+    if (clientW <= 0 || clientH <= 0) {
+        s_adjustingForce43 = false;
+        return;
+    }
+
+    // Decide which dimension the user changed most – adjust the other
+    int curW = static_cast<int>(width() / dpr);
+    int curH = static_cast<int>((height() - chromeH) / dpr);
+    bool widthChanged = std::abs(clientW - curW) >= std::abs(clientH - curH);
+
+    int targetW, targetH;
+    if (widthChanged) {
+        // user dragged width – compute matching height for 4:3
+        targetW = clientW;
+        targetH = (clientW * 3) / 4;
+    } else {
+        // user dragged height – compute matching width for 4:3
+        targetH = clientH;
+        targetW = (clientH * 4) / 3;
+    }
+
+    // Convert back to window size including chrome and apply
+    int newW = static_cast<int>(targetW * dpr);
+    int newH = static_cast<int>(targetH * dpr) + chromeH;
+    if (newW != winW || newH != winH)
+        resize(newW, newH);
+
+    // Update emulator framebuffer size and notify platform
+    monitors[0].mon_scrnsz_x = targetW;
+    monitors[0].mon_scrnsz_y = targetH;
+    plat_resize_request(targetW, targetH, 0);
+
+    // Allow renderer widget to grow and recompute scaling
+    ui->stackedWidget->setFixedSize(QWIDGETSIZE_MAX, QWIDGETSIZE_MAX);
+    ui->stackedWidget->onResize(width(), height());
+
+    s_adjustingForce43 = false;
+}
+
 void
 MainWindow::resizeEvent(QResizeEvent *event)
 {
     //qDebug() << pos().x() + event->size().width();
     //qDebug() << pos().y() + event->size().height();
+	
+    // Enforce 4:3 aspect ratio in resizable mode when the option is set
+    adjustForForce43(event->size());
+	
     if (vid_resize == 1 || video_fullscreen)
         return;
 
@@ -2075,6 +2141,17 @@ void
 MainWindow::on_actionForce_4_3_display_ratio_triggered()
 {
     video_toggle_option(ui->actionForce_4_3_display_ratio, &force_43);
+
+    // When turning on Force 4:3 in resizable mode, immediately snap to 4:3
+    if (vid_resize == 1 && !video_fullscreen) {
+        ui->stackedWidget->setFixedSize(QWIDGETSIZE_MAX, QWIDGETSIZE_MAX);
+        if (force_43 > 0) {
+            adjustForForce43(size());
+        } else {
+            // Turning off: refresh renderer scaling
+            ui->stackedWidget->onResize(width(), height());
+        }
+    }
 }
 
 void
diff --git a/src/qt/qt_mainwindow.hpp b/src/qt/qt_mainwindow.hpp
index 6a255ac85..792685f42 100644
--- a/src/qt/qt_mainwindow.hpp
+++ b/src/qt/qt_mainwindow.hpp
@@ -176,6 +176,9 @@ private:
     std::unique_ptr<MachineStatus> status;
     std::shared_ptr<MediaMenu>     mm;
 
+    static bool s_adjustingForce43; // guard against recursion
+	void adjustForForce43(const QSize &newWinSize);
+    
 	void updateShortcuts();
     void     processKeyboardInput(bool down, uint32_t keycode);
 #ifdef Q_OS_MACOS