diff --git a/tilorswift/js/module.js b/tilorswift/js/module.js
index 577fcb9..05f34a3 100644
--- a/tilorswift/js/module.js
+++ b/tilorswift/js/module.js
@@ -6,6 +6,13 @@ import Setting from "../../js/Setting.js";
 
 const imageLoader = new ImageLoader();
 
+window.addEventListener(
+    'beforeunload',
+    (event) => {
+        event.preventDefault();
+    }
+);
+
 for (const graphicSet of GraphicSet) {
     imageLoader.addImage('../' + Setting.TILESET_LOCATION + graphicSet.tileset);