Share the screen of another Mac
While your screen is being shared, the user of the other Mac sees what’s on your screen and can open, move, and close files and windows, open apps, and even restart your Mac.
Before you start, make sure the Mac whose screen you want to view has screen sharing turned on. See Turn Mac screen sharing on or off.
Start a screen sharing session with another Mac
If you’ve been given permission, you can view and control the screen of another Mac on your network.
On the Mac you want to share, choose Apple menu
, select Screen Sharing, then note the name and address of the Mac (it’s listed on the right). The name looks like “iMac (7)” or “Joe’s MacBook Pro.”
The address looks like vnc://[IPAddress] or vnc://[Name.Domain].
On your Mac, do one of the following:
Connect using the name: Click the Finder icon
in the Dock to open a Finder window. In the Locations section of the sidebar, click Network, double-click the Mac you want to share, then click Share Screen.If no items appear in the Locations section of the sidebar, hold the pointer over the word Locations, then click the arrow
.Connect using the address: In the Finder, choose Go > Connect to Server, enter the address of the Mac you want to share, then click Connect.
If prompted, enter your user name and password, then click Sign In.
If both computers are logged in using the same Apple ID, the screen sharing session starts. If they’re not, you’re prompted to enter the user name and password of a user who is allowed screen sharing access on that computer, or you can request permission to share the screen if the computer allows it.
If someone else is already connected to the Mac as a remote user, a dialog asks if you want to share the display with the other remote user (Share Display) or log in concurrently using a different user name and screen (Log In).
If you choose Log In, you share the Mac with the other remote user, but you won’t share the same screen.
Set screen sharing preferences
When you’re sharing the screen of another Mac, you can set screen sharing preferences to adjust the size and quality of the shared screen.
On your Mac, start a screen sharing session with another Mac on your network.
Choose Screen Sharing > Preferences, then set the following options:
Under Display, select “Scale to fit available space” or “Show full size,” depending on how large your screen is and how much of it you want to use for the shared screen. This option changes the default behavior for when you share the screens of computers you’ve never connected to before. To change the current scale, choose View > Turn Scaling Off or View > Turn Scaling On.
Under Display, select a “Scroll the screen” option to determine how the screen sharing window behaves when you move the pointer. To decide which option you want, try each one by selecting it and then moving the pointer around in the window.
Under Quality, select “Adapt quality to network conditions” to view the shared screen more quickly, or “Show the screen at full quality” for a more detailed view of the shared screen. This option changes the default behavior for when you share the screens of computers you’ve never connected to before. To change the current scale, choose View > Adaptive Quality or View > Full Quality.
For the best results, and if your Mac is connected to a fast network, view the screen at full size and show the screen at full quality.
Under Blocked Users, choose an option from the “Allow screen sharing requests from” pop-up menu to enable sharing your screen with either everyone who tries to connect to your computer using an Apple ID or just your contacts.
To block users with specific Apple IDs from sharing your screen, click the Add button
, enter the user’s Apple ID, then click Block. To unblock users, select them in the list and click the Remove button 
.
Set view options while sharing another computer’s screen
When you’re sharing the screen of another Mac, your viewing options depend on your network connection and the size of the screen you’re sharing.
On your Mac, start a screen sharing session with another Mac on your network.
From the View menu, set the following options:
Show Tab Bar: Use this option to display or hide the tab bar.
Turn Scaling On/Off: With scaling on, the entire screen of the shared Mac is displayed on your screen. With scaling off, the shared screen is displayed full size, and might require you to scroll to see everything on the shared screen.
Switch to Observe Mode/Switch to Control Mode: In Observe mode, you can watch what’s happening on the shared screen, but you can’t control the pointer, move windows, open and close documents, or do other tasks. If you’re observing OS X 10.9 or later, you can click and hold to highlight the screen at your pointer. In Control Mode, you control the shared screen.
Adaptive Quality: Use this option if your Mac is connected to a slower network. Adaptive quality adjusts depending on network speed.
Full Quality: Use this option if your Mac is connected to a fast network and you want full resolution.
Show/Hide Toolbar: Show or hide the toolbar that displays buttons for adjusting the scale, sharing the Clipboard, and other options.
Customize Toolbar: Drag buttons into or out of the toolbar.
Enter Full Screen: The screen sharing window expands to fill your screen. To see the toolbar and menus, move the pointer to the top of the screen.
Displays: If the Mac whose screen you’re sharing has more than one display, you can choose which display you want to view.
Share the contents of the Clipboard with another Mac
When you’re sharing one computer’s screen with another computer, you can transfer information between the Clipboards of the two computers. For example, you can:
Copy text and images from documents on one Mac and paste them into documents on the other.
Select and drag text and images from one Mac to the other.
Copy a link from your web browser and paste it into a web browser on the other Mac.
Copy text from a document on one Mac and drop it on the desktop of the other Mac to create a clipping.
On your Mac, start a screen sharing session with another Mac on your network.
Choose Edit > Use Shared Clipboard.
You can also use Universal Clipboard to copy text, images, photos, and video on one Apple device and then paste the content on another Apple device.
Send files while sharing another computer’s screen
When you’re sharing one computer’s screen with another computer, you can transfer files between the two computers.
On your Mac, start a screen sharing session with another Mac on your network.
Select a file or folder, then drag and release the files over the screen sharing window.