diff --git a/web/chat/edit-text-message.react.js b/web/chat/edit-text-message.react.js
--- a/web/chat/edit-text-message.react.js
+++ b/web/chat/edit-text-message.react.js
@@ -87,15 +87,28 @@
     });
   }, [background, updatePosition]);
 
+  const preventCloseTab = React.useCallback(
+    event => {
+      if (!isMessageEdited) {
+        return null;
+      }
+      event.preventDefault();
+      return (event.returnValue = '');
+    },
+    [isMessageEdited],
+  );
+
   React.useEffect(() => {
     if (!background) {
       return undefined;
     }
     window.addEventListener('resize', updateDimensions);
+    window.addEventListener('beforeunload', preventCloseTab);
     return () => {
       window.removeEventListener('resize', updateDimensions);
+      window.removeEventListener('beforeunload', preventCloseTab);
     };
-  }, [background, updateDimensions]);
+  }, [background, preventCloseTab, updateDimensions]);
 
   React.useEffect(() => {
     updateDimensions();