diff --git a/src/emu/machine.cpp b/src/emu/machine.cpp
index e32d8f73..1e1e23c5 100644
--- a/src/emu/machine.cpp
+++ b/src/emu/machine.cpp
@@ -1328,16 +1328,31 @@ void running_machine::emscripten_main_loop()
 
 	auto profile = g_profiler.start(PROFILER_EXTRA);
 
+	// the page reads game controllers here, so the step sees the newest input
+	EM_ASM({ if (Module.beforeStep) Module.beforeStep(); });
+
 	// execute CPUs if not paused
 	if (!machine->m_paused)
 	{
 		device_scheduler * scheduler;
 		scheduler = &(machine->scheduler());
 
-		// Emscripten will call this function at 60Hz, so step the simulation
-		// forward for the amount of time that has passed since the last frame
-		const attotime frametime(0,HZ_TO_ATTOSECONDS(60));
-		const attotime stoptime(scheduler->time() + frametime);
+		// Step the simulation forward by the real time since the last browser
+		// frame, so its speed does not depend on the display's refresh rate.
+		// The clamp stops a jump after the tab has been in the background.
+		// The stop time carries over, so a step that runs long shortens the next.
+		static double last_ms = 0.0;
+		static attotime stoptime;
+		const double now_ms = emscripten_get_now();
+		double seconds = 1.0 / 60.0;
+		if (last_ms)
+			seconds = (now_ms - last_ms) / 1000.0;
+		else
+			stoptime = scheduler->time();
+		last_ms = now_ms;
+		if (seconds > 0.1)
+			seconds = 0.1;
+		stoptime += attotime::from_double(seconds);
 
 		while (!machine->m_paused && !machine->scheduled_event_pending() && scheduler->time() < stoptime)
 		{
@@ -1354,6 +1369,9 @@ void running_machine::emscripten_main_loop()
 	else
 		machine->m_video->frame_update();
 
+	// the page draws in the same browser frame, so the picture is not a frame late
+	EM_ASM({ if (Module.afterStep) Module.afterStep(); });
+
 	// cancel the emscripten loop if the system has been told to exit
 	if (machine->exit_pending())
 	{