Screen Sharing – the ability to see and control another computer remotely — is a very easy and potent way to offer remote tech support and utilize capabilities and software packages not present on the controlling device.

As an extreme example, a powerful desktop computer can be controlled from a tablet or smart-phone — easy to set up, though, arguably, less-so to control using your finger.

This is the latest in in the Mac Sharing series, where we’ve also covered:

Level: Switcher / Intermediate

In this guide, we will look at some of the methods of sharing screens between Macs, Windows PCs, iOS and Linux / Android devices over a local network or via the Internet.

Security first

Despite the degree of control it delivers, screen sharing is easier to set up than file sharing. This tends to mask its security concerns in the minds of users. Due to the fact that remote desktop capability effectively gives someone complete control over another user’s computer, security considerations should take high priority. For instance, the remote computer will most likely have access to all signed in services on the target computer’s web browser, and will easily be able to install software and make changes to security settings not possible via conventional file-sharing.

When offering tech support via screen sharing it’s probably good tech-etiquette to inform less knowledgeable target users of these considerations and even advise them to watch the session for peace of mind.

Mac to Mac on a local network

See Apple’s short support page for full details. Here’s the super-quick method.

On the target Mac perform or instruct the target user to perform these changes:

  1. Go to the Apple Menu (top left) and choose System Preferences
  2. Click on the yellow Sharing Preferences icon (3rd down, 4th or 5th left)
  3. Turn on and select Screen Sharing in the left sidebar of the panel
  4. Choose All users; or Only these users: and add users who are allowed to share the that particular Mac’s screen. Administrators include anyone who knows the credentials of that Mac.
  5. On the controlling Mac look for the target Mac in the sidebar of a Finder window and select it.
  6. Click the Share Screen… button. Enter the username and password of the target Mac.
Click to enlarge.

The built-in Mac Screen Sharing App will launch and connect to the target Mac. Click on Screen’s menus to get a feel for the range of options.

Control Windows from a Mac on a LAN


For seeing and controlling Windows on a Mac, a free / open-source, out-of-the-box local network remote desktop app called Cord is well-recommended (reviewed by Tech Republic in 2012), and utilizes the kernel-level RDP protocol, resulting in good quality and performance over a local network. The software is similar to Microsoft RDP for Mac, but unlike that app, it is up-to-date and stable. It utilizes built-in Windows services and therefore requires changing settings in Windows. Cord also has the limitation of hiding the remote PC’s desktop behind the login screen, which makes it less desirable for scenarios where the other user needs to see what you’re doing.

Windows, Mac, iOS and Linux / Android remote desktop

If you want to be overwhelmed, look at Wikipedia’s huge comparison page, or stay here for a quick roundup.


The robust grand-daddy stalwart (origins going back to 1998) of remote desktop is RealVNC (free open-source edition, $30 personal, $50 per enterprise desktop).

Chrome Remote Desktop

The excellent free, browser-based Chrome Remote Desktop offers internet remote desktop for Chrome users with a Google account.

Internet / LAN remote desktop options

LogMeIn, and the slightly newer kid: TeamViewer, both offer enterprise-class solutions with free-for-personal-use options.


Although the performance is reportedly slightly slower than LogMeIn, the ease of setup and usage, and wide range of device support is the reason I’m recommending TeamViewer as a one-stop-shop for all remote-desktop tasks (besides the aforementioned Mac-to-Mac LAN Screen Sharing). Read more about TeamViewer extensively on Tech Republic.

After a quick, all-defaults installation of TeamViewer you can use it to access almost any platform remotely from any device: Mac, Windows, Linux, iOS and Android are all supported with a fairly uniform interface for keeping that learning curve shallow.

Another security reminder

As you might expect, this ease of setup comes at a price: security. TeamViewer has been a favourite among attackers offering to “fix” your computer (and bank account) over the phone; and a documented exploit occurred in Hungary using version 6 of TeamViewer for Windows, so make sure you’re using the latest version.

Installing TeamViewer

After downloading the app / program for your platform from, proceed with a default installation. On a Mac: Continue, Continue, Agree, Install, enter password, OK, Close.

When launching for the first time you will be greeted by the SetupAssistent (the spelling is a clue to TeamViewer’s home in Germany). Bypass the Assistent by clicking Continue, Agree, Skip, Finish unless you want to access that computer remotely at a later stage.

Two panels appear: the TeamViewer main panel (usually on the left) is split into two sections: Allow Remote Control with your ID on the left; and Control Remote Computer on the right.

That ID doesn’t change, only the password after each session.

  1. Obtain your partner’s ID and one-time password
  2. Enter the ID into the Partner ID field
  3. Click the Connect to partner button
  4. Enter the password

TeamViewer connects to the remote device. At the top of the TeamViewer window you can set quality options.

The session can be ended by closing the window to the other computer, or via the session panel on the computer being controlled.

TeamViewer over LAN

TeamViewer has LAN access off by default, but for improved quality, or for security reasons you can turn it on, exclusively if desired.

To change the LAN setting:

  1. In TeamViewer – Preferences, or on Windows in the menu click on Extras and then on Options
  2. Choose the General tab and change the drop-down menu to Accept incoming LAN connections

When selecting accept exclusively it will display the IP-address of the computer in the ID field. Connect using the IP address or using the host name.

TeamViewer on tablets and smartphones

Installation on smart devices is even easier. Try controlling your computer from a tablet. You may decide that it’s too fiddly at that scale, but that sort of usage is certainly not unheard-of:

Actual scenario: I once set up TeamViewer for a surgical anesthetist on an iPad — considered more clinically sterile than a laptop which is a potential nest for bacteria. He was able to access certain specialist apps only available on his desktop Mac.