Stream content on a larger screen with AirPlay
Use AirPlay to stream whatever’s on your iMac to the big screen—or use AirPlay to send content to your Mac from an iPhone, iPad, or even another Mac. You can mirror the iMac screen on your TV screen or use a high-resolution TV as a second display. To do so, connect your TV to Apple TV and make sure Apple TV is on the same Wi-Fi network as your iMac. You can also play web videos directly on your TV without showing what’s on your desktop—handy when you want to play a movie but keep your work private.
Mirror your desktop using Screen Mirroring. Click the Control Center icon 
in the menu bar, click Screen Mirroring 
, then choose your Apple TV. When AirPlay is active, the icon turns blue.
Note: If your Mac supports AirPlay screen mirroring, you see an AirPlay status icon in the menu bar when an Apple TV is on the same network as your Mac. See Use AirPlay to stream video or mirror your device’s screen.
Send content to your Mac from other devices. Watch videos, listen to music, and more on your Mac while they’re being played on your other devices. Mirror your iPhone or iPad on your Mac or extend its display by using your Mac as a secondary display for apps that support it, such as Keynote and Photos. Use your Mac as an AirPlay 2 speaker to stream music or podcasts to your Mac, or use it as a secondary speaker for multiroom audio. Your Mac works with any Apple device, and it’s even easier to connect if the devices share the same Apple ID.
Play web videos without showing your desktop. When you find a web video with an AirPlay icon 
, click the icon, then select your Apple TV.
Apple TV is sold separately at apple.com or your local Apple Store.
Tip: If the image doesn’t fit your high-resolution TV screen when you mirror the screen, adjust the desktop size for the best picture. Click the AirPlay icon in the video, then choose an option under Match Desktop Size To.