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This chapter is from the book

This chapter is from the book

Sharing Your iMac Screen

Chapter 6, “Keeping Contacts, Appointments, Reminders, and Notes,” includes instructions on how to share your Macintosh’s screen using Messages, but there are many instances where you might want to access another Mac’s display without having to start a chat.

Built into Mountain Lion is a standards-based screen-sharing system. Using screen sharing, you can access your Mac’s display from anywhere on your local network or, in some cases, from anywhere in the world. New in Mountain Lion is the ability to share a computer’s “screen” even if someone else is using the computer. The screen sharing software can now automatically create a virtual screen that you can see and use while the person sitting in front of the computer continues to see their own desktop!

Enabling Screen Sharing

To configure another Mac so that you can access its screen from your iMac, you initially need direct access to the computer:

  1. In the System Preferences window, click the Sharing icon.
  2. Click the checkbox in front of the Screen Sharing service.
  3. A URL that you can use to connect to your computer is displayed on the right side of the sharing pane.
  4. Close the System Preferences, or continue setting sharing preferences.

Setting Screen Sharing Permissions

After screen sharing is enabled, choose who can access the display. Initially, only administrative users can view your screen.

  1. In the System Preferences window, click the Sharing icon.
  2. Click the Screen Sharing service label.
  3. Choose whether All Users on the computer can access its screen, or click Only These Users to restrict access to specific individuals or groups.
  4. Use the + button to choose a user or group that should be granted access, or use – to remove a user or group that you had previously added.
  5. A window for selecting a user displays. Choose the user or group and click Select.
  6. For additional control, click the Computer Settings button.
  7. In the dialog box that appears, click Anyone May Request Permission to Control Screen to allow anyone to access the display if the person sitting in front of the computer grants them access.
  8. To provide access to your Mac’s screen using a standard VNC (Virtual Network Computing) client, click the VNC Viewers May Control Screen with Password checkbox and provide a password that grants access to those users.
  9. Click OK.
  10. Close the System Preferences.

Accessing the Screen of a Local Mac

To access the shared screen of a Mac on your local network, make sure that your iMac is connected to the network and then follow these steps:

  1. Open a new Finder window and make sure the Shared sidebar section heading is expanded.
  2. Click the computer whose screen you want to access.
  3. Click Share Screen in the upper-right corner of the Finder window.
  4. Enter your username and password on the remote system, if prompted.
  5. Click Remember This Password in My Keychain to store the password and enable password-less connections in the future.
  6. Click Connect to begin using the remote display.
  7. If another person is using the computer, you can ask to share the display with them, or connect to a new virtual display. Click whichever approach you prefer.
  8. The remote display is shown in a window on your iMac.
  9. Toggle between controlling and observing with the Control Mode icon in the toolbar.
  10. Use the Scaling Mode icon to view the screen fullsize or shrink it to fit your window.
  11. Click the Capture Screen item to save a screenshot of the current screen.
  12. Use Get Clipboard to transfer the contents of the remote computer’s clipboard into your local clipboard, and Send Clipboard to transfer your clipboard to the remote system.
  13. Click Shared Clipboard to share a single clipboard between the two systems.
  14. Close the window when you’re finished using the remote system.

Accessing Remote Computers and Non-Macs

If you can’t browse to a computer to access its screen, or you need to connect to a non-Macintosh computer, you can do so using almost the same process as you used to connect to a remote file share:

  1. When you’re sharing a screen on your iMac, Mountain Lion provides you with a URL that can be used to access your screen, even if you can’t browse to it on the network.
  2. Choose Go, Connect to Server from the Finder menu bar.
  3. Enter the screen-sharing URL in the Server Address field. Alternatively, if you only have an IP address (such as, prefix the IP address with vnc:// to create a properly formed URL (for example, vnc://
  4. Click + if you want to add the server to the list of favorite servers.
  5. Click Connect to connect to the remote server’s screen.
  6. Enter a username (and/or password), if prompted, and click Connect.
  7. The remote display is shown in a window on your iMac.

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