How to Prevent Notifications when Screen Mirroring on a Mac

To prevent notifications from appeared on mirrored screens, click the Notification Center button → click the Do Not Disturb slider. Click the Notification Center button. This is located in the upper-right corner of the screen.

Part 1 of 2:

Click the Notification Center button. This is located in the upper-right corner of the screen.
Click the Do Not Disturb switch.
Click the Notification Center button to close the panel.

Part 2 of 2:

Click the Apple menu.
Click System Preferences. Click the Show All button at the top of the System Preferences window if the regular options don't appear. The Show All button has an icon of 12 dots in a grid.
Click the Notifications option.
Click Do Not Disturb.
Click the When mirroring to TVs and projectors box.^[1]