Do websites that auto-play ads or videos drive you mad? (They should.) Especially when you reopen Safari and several of them in remembered tabs start playing simultaneously? Crazy-making.
Since OS X 10.11 El Capitan, Safari can put an end to that cacophony on your Mac. Whenever audio is playing in a tab, an audio icon appears next to the name of the tab and at the right of Safari’s Smart Search field. Click either one to mute the tab.
If you’ve ended up with multiple tabs playing, you can mute all those except the current tab by Option-clicking either of those audio icons. And, finally, click and hold the audio icon in the Smart Search field for a menu with Mute and Unmute commands, and a list of all tabs that contain audio.