Make your Mac flash the screen when an alert sounds

Why it happens

Your Mac plays a short alert sound when something needs your attention or a key isn't allowed. If you're deaf or hard of hearing, or wear headphones, that sound is easy to miss. This setting makes the whole screen flash briefly each time the alert sound plays.

How to fix it

1. Open System Settings and click Accessibility in the sidebar.

2. Click Audio and turn on Flash the screen when an alert sound occurs. Turn it off to stop the flashing.

   Accessibility›Audio›Flash the screen when an alert sound occurs

3. To test it, click the Test button next to the switch. Or click in an empty search field and press Delete: your Mac plays its alert sound, and the screen should flash.

Still not fixed?

1. Notifications from apps don't always make the screen flash. To be sure you see them, open Notifications, pick the app and choose Persistent, so its alerts stay on screen until you close them.

   Notifications

2. Want the beep louder or quieter as well? Drag Alert volume in Sound > Sound Effects.

   Sound›Sound Effects

3. If the screen flashes when you didn't expect it, something is setting off the alert sound, often a stuck key or something resting on the keyboard.

4. If the screen flickers or flashes with this setting off, that isn't an alert. Restart your Mac, and if it carries on, it may be a display fault: contact Apple Support or a repair shop.