diff --git a/xwords4/wasm/main.c b/xwords4/wasm/main.c
index 09e60c2a2..fb97d53ce 100644
--- a/xwords4/wasm/main.c
+++ b/xwords4/wasm/main.c
@@ -569,6 +569,14 @@ updateScreen( Globals* globals, bool doSave )
     }
 }
 
+static void
+doExit( Globals* globals )
+{
+    call_alert( "Control passed to another tab" );
+    XP_MEMSET( globals, 0, sizeof(*globals) ); /* stop everything :-) */
+    // emscripten_cancel_main_loop(); <-- does nothing
+}
+
 static void
 looper( void* closure )
 {
@@ -605,6 +613,8 @@ button( void* closure, const char* msg )
     } else if ( 0 == strcmp(msg, "vals") ) {
         globals->cp.tvType = (globals->cp.tvType + 1) % TVT_N_ENTRIES;
         draw = board_prefsChanged( board, &globals->cp );
+    } else if ( 0 == strcmp(msg, "exit") ) {
+        doExit( globals );
     }
 
     if ( draw ) {
diff --git a/xwords4/wasm/shell_minimal.html b/xwords4/wasm/shell_minimal.html
index 909a379cf..7b4f9dea1 100644
--- a/xwords4/wasm/shell_minimal.html
+++ b/xwords4/wasm/shell_minimal.html
@@ -55,6 +55,7 @@
 		  position: absolute;
 		  text-align: left;
 		  z-index: 10000;
+		  white-space: pre-wrap;
 		  left: 33%;
 		  top: 250px;
 		  width: 33%;
diff --git a/xwords4/wasm/xwutils.js b/xwords4/wasm/xwutils.js
index 4decd42fc..6f2b6ff5f 100644
--- a/xwords4/wasm/xwutils.js
+++ b/xwords4/wasm/xwutils.js
@@ -16,7 +16,17 @@ function callButton(obj) {
 }
 
 function onHaveDevID(closure, devid) {
-    console.log('got ' + devid);
+	// Set a unique tag so we know if somebody comes along later
+	let tabID = Math.random();
+	localStorage.setItem('tabID', tabID);
+	window.addEventListener('storage', function () {
+		newTabID = 	localStorage.getItem('tabID');
+		if ( newTabID != tabID ) {
+			state.client.disconnect();
+			Module.ccall('button', null, ['number', 'string'], [state.closure, 'exit']);
+		}
+	} );
+
 	state.closure = closure;
 	document.getElementById("mqtt_span").textContent=devid;