The more screen space you have, the more efficiently you work, apparently. So why not connect a second display to your Mac? In this article we help you identify which adapter you need to plug your Mac into an extra, external screen (or even more than one), and how to get everything set up.

While it's generally easy to set up a second screen, there are a few issues that might cause your display not to work, and we will also offer solutions for these.

A final note before we start. When Apple introduced macOS Sierra in September 2016 it appears that it may have stopped some third-party adapters working with extra displays. If you have had issues getting your second display to work let us know in the comments below.

How to connect an external monitor to a Mac

  1. Identify which Apple adapter and cable you need to connect the Mac and the monitor by following the guidance below.
  2. Plug it in.
  3. Open System Preferences > Displays.
  4. Click the Arrangement tab.
  5. Do not select the Mirror Displays tickbox (unless you want the second screen to show the same content as your original screen).
  6. Drag the illustrated displays into the arrangement you require. A white menu will be shown on the main screen (although since the launch of OS X Mavericks all screens can have a menu bar). Drag this white bar to the screen you wish to be dominant.

If you want to mirror the display on both (or multiple) displays go to System Preferences > Displays > Arrangement and choose Mirror Displays.

You can also select 'Show mirroring options in the menu bar when available' and you will see a status menu in the menu bar making it easier to turn this off and on again.

If you have an Apple TV you can use AirPlay to send a second screen output to your TV. Here's how to do that: How to view your Mac screen on a TV.

If you are using your Mac with an external screen and want to close the lid on your MacBook here's How to use MacBook with lid closed, stop closed Mac sleeping.

Which port have I got?

The adapter you require depends on the model of Mac and the type of monitor. Apple has implemented quite a few different port types over the years, and your iMac or MacBook might feature any of the following:

Mini DisplayPort

Mini DisplayPort was announced by Apple towards the end of 2008. With an adapter, the Mini DisplayPort can drive displays that feature VGA, DVI or HDMI interfaces. This is what Mini DisplayPort looks like.

How to use a second screen with a Mac: Mini DisplayPort


The Thunderbolt port, first introduced in 2011, looks the same as Mini DisplayPort (and is backwards-compatible). If you see a thunderbolt symbol besides what looks like a Mini DisplayPort, your Mac has a Thunderbolt port.

Thunderbolt has appeared on Macs since around 2011, so if your Mac is from after that year, chances are it offers Thunderbolt rather than Mini DisplayPort, although the two are compatible.

You can use a Mini DisplayPort adapter in a Thunderbolt port but you can also use Apple's Thunderbolt to Gigabit Ethernet Adapter or Thunderbolt to FireWire Adapter with it. A Thunderbolt-equipped Mac can connect a 4K Ultra HD TV via a direct HDMI connection, or via a Thunderbolt to high-speed HDMI adapter.

In 2013 Apple introduced Thunderbolt 2, which is faster than Thunderbolt 1, but the port is the same.

Thunderbolt 3 or USB-C

From around the end of 2016 Apple started equipping its higher-end systems with Thunderbolt 3, which connects devices to your computer at up to 40Gbps. The connection looks the same as USB-C:

How to use a second screen with a Mac: MacBook Pro 2016

Unfortunately, if you were hoping to plug your new MacBook Pro into a second display you may be out of luck as the Macs that use Thunderbolt 3 or USB-C won't work with any of the following adapters, even if you use a Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter.

  • Apple Mini DisplayPort to Dual-Link DVI Adapter
  • Apple Mini DisplayPort to DVI Adapter
  • Apple Mini DisplayPort to VGA Adapter
  • Apple LED Cinema Display

Now that you've identified which port your Mac has you need to check the port on your display, it is likely to offer one of the following:


A VGA connector requires a three-row 15-pin DE-15 connector. VGA connectors transmit analogue signals.

Old CRT (Cathode Ray Tube) monitors were VGA but there are flat displays that use VGA - they just convert the VGA connector's analog signal back to digital. This conversion from digital to analog and back again can cause degradation of video quality. VGA will carry HD video but only analogue audio.

Apple sells a number of VGA adapters.

How to use a second screen with a Mac: VGA


DVI offers a higher-quality signal than VGA because it's a digital signal. You will see a marked difference when looking at HD video as compared to VGA.

A DVI connector has the potential for 24 pins, depending on whether it's DVI-A, DVI-D or DVI-I, there are different connectors with a different number of pins in use. There is also a long pin which may be surrounded by four other pins (which are required for audio in older models).

Apple's Mini DisplayPort to DVI Adapter has holes for all 24 pins but not the four pins that surround the long pin.

How to use a second screen with a Mac: DVI


The main difference between DVI and HDMI is that HDMI supports up to eight channels of audio, while DVI supports video only. HDMI 2.1 brings support for resolutions up to 8k and higher. HDMI is the most common connector you'll find on the back of a TV.

Here are Apple's HDMI adapters.

How to use a second screen with a Mac: HDMI


If you purchased the Apple Thunderbolt display, which was discontinued in 2016, then your monitor has a Thunderbolt port, as seen above.

Mini DisplayPort

If you have one of Apple's LED Cinema Displays, introduced back in 1999 and replaced in 2011 by the Thunderbolt display, your display has a Mini DisplayPort connection, as seen above.

(For more information about ports, here's a run down of some of Apple's different port types.)

What cable should I buy?

You will also need a cable to connect your Apple adapter to the monitor. This cable doesn't need to be from Apple, but it will need to have the right connections.

Is the port male or female?

You need to check whether the connection on the back of your display has female or male endpoints. The Apple adapters are female, so if the port on the back of your monitor is also female (in other words has holes not spikes) you will need a male to female adapter. Our NEC MyltiSync E243WMI has a female connection.

Which adapter do I need?

You can buy adapters from a number of third parties, and they may well be cheaper than Apple's offerings. However, it appears that since Apple unleashed macOS Sierra many of these third-party adapters no longer work, so we would recommend that you buy an Apple adapter.

Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter

Apple's Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter can be used to connect to a Thunderbolt display. It costs £49/$49 and can be purchased here.

USB-C Digital AV Multiport Adapter

Among other things, the Apple USB-C Digital AV Multiport Adapter lets you connect a Thunderbolt 3-equipped Mac to an HDMI display. You will need a separate HDMI-to-HDMI cable (such as this one from Belkin) to do so.

The USB-C Digital AV Multiport Adapter costs £69/$69, and you can buy it here.

USB-C VGA Multiport Adapter

Apple's USB-C VGA Multiport Adapter lets you connect to a VGA display or projector. This is an analogue connection so it will not support HDCP (High-bandwidth Digital Content Protection) content. This would include the HD movies found on the iTunes Store.

The USB-C VGA Multiport Adapter costs £69/$69 and is available here.

Mini DisplayPort to VGA Adapter

Apple's Mini DisplayPort to VGA Adapter can be used to connect a Mac with Mini DisplayPort or Thunderbolt ports to a external display or projector that uses VGA. It costs £29/$29 and can be purchased here.

Mini DisplayPort to DVI Adapter

Apple's Mini DisplayPort to DVI Adapter can be used to connect a Mac with Mini DisplayPort or Thunderbolt ports to an external display or projector that uses DVI.

Mini DisplayPort features on most Macs and is used to connect to an external display. Using an adapter you will be able to use it to connect your Mac to a DVI or VGA display.

This is for displays that do not support Dual-link DVI resolutions (DVI displays with a resolution of 1920 x 1200 or lower). DVI will support HDCP content.

It costs £29/$29 and can be purchased here.

Mini DisplayPort to Dual-Link DVI Adapter

Wondering what the difference is between single-link DVI and dual-link DVI? Dual-link is for DVI displays with resolutions above 1920 x 1200. When you use the Apple Mini DisplayPort to Dual-Link DVI adapter (£99/$99), your Mac will need a free USB port.

If your display operates at 1920 x 1200 or lower you should use the Apple Mini DisplayPort to DVI adapter instead. It costs £29/$29 from Apple and you can purchase it here.

Mini DisplayPort to HDMI adapters

Apple does not manufacture a Mini DisplayPort to HDMI adapter.

Troubleshooting problems

There are a number of issues you may experience with your display setup. Here we address some of them. Let us know of any further solutions or problems in the comments below.

External display is not working with a Mini DisplayPort adapter

If your adapter is not made by Apple, that might just be the issue here. Prior to macOS Sierra it was possible to use a third-party Mini DisplayPort to DVI adapter with a Mac, but since Sierra launched Mac users who were reliant on that setup have found their monitors have stopped working with their Mac.

The only solution if this is the case is to purchase an Apple adapter.

If you have an Apple adapter and your external display isn't working, try the following:

  1. Disconnect your adapter for a few seconds.
  2. Reconnect it and see if the issue persists.
  3. Disconnect the adapter again and power off the monitor.
  4. If it's still not working, connect the cable again and power off the display.
  5. If when you turn the display back on it's still not working, click on the Apple logo and choose Sleep.
  6. Wait a few minutes and then move your mouse or tap your keyboard to wake your Mac.
  7. If that doesn't work, restart the computer.
  8. Try adjusting the display's brightness or contrast just in case it's turned down.
  9. Go to System Preferences > Display and try selecting a different resolution.
  10. If that still doesn't work, try restarting your Mac in safe mode and then reset the display resolution to defaults.
  11. Another option is to reset the Mac's NVRAM and SMC.

Mac won't detect the external display

When you connect your display and your Mac the display should automatically be detected. But what should you do if it isn't?

As we explain above, if your adapter is not made by Apple that might just be the issue here. If you are using an Apple adapter, try the following:

  1. Connect your monitor and Mac and open System Preferences > Displays.
  2. Press the Alt/option key. This should make the Detect Displays button appear.
  3. Click on Detect Displays. This should cause your Mac to see the external monitor.

DVI adapter doesn't fit in the connection

There are a few possible reasons why the Apple Mini DisplayPort to DVI adapter might not be compatible with your monitor.

There is more than one kind of DVI adapter and the likelihood is the one you have is different to the adapter you are using. For example, you may require space for four analog ports around the flat blade.

If your problem is that you have two female or two male connections then the solution is to buy a male-to-female adapter.

Cable too small between the two devices? You should be able to hook up your adapter to the screen via a third-party cable. Just make sure it has the correct port type.

How to connect a Thunderbolt 3 MacBook Pro

You can use the Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter to connect a 2016 or later MacBook Pro with Thunderbolt 3 (USB-C) ports to a Thunderbolt display, but what if you haven't got a Thunderbolt display?

To connect to a DVI display you need a USB-C to DVI cable or adapter and Apple doesn't make one. You may be able to find one, but we can't guarantee that it will work as it appears third-party adapters do not work with Macs that have been updated to macOS Sierra and later.

Similarly Apple doesn't make a USB-C to Mini DisplayPort adapter, so you won't be able to connect a 2016 or later MacBook Pro to the Apple Cinema Display which uses a Mini Display Port and as such is not compatible with the MacBook Pro.

How to connect a third monitor to a Mac

Theoretically you shouldn't be able to attach a monitor to a USB port, but a few companies have treated this as a technical challenge. The Matrox DualHead2Go and TripleHead2Go let you connect up to two or three external displays respectively. They do this by augmenting the standard DVI/HDMI video output of a Mac or PC with data provided via a USB 2.0/3.0 connection.

To learn if your Mac is compatible, check out Matrox's Mac compatibility listing, where you'll also learn the maximum possible output resolutions - it's unlikely you'll be able to run all three displays at 1080p, for example.

Diamond MultiMedia's BVU range lets you run a separate external display via nothing more than a USB 2.0 port. By connecting one to a MacBook Pro, as one example, you could utilise up to three displays: one built in, one via the existing DVI/HDMI/DisplayPort, and one more via USB.

There are also some no-brand devices on eBay and Amazon that offer the same functions as the Diamond product, and are cheaper to boot - although be sure to check for Mac compatibility. Just search for something like USB to DVI HDMI.

All the above solutions are somewhat hacky. We haven't tested any but we're certain performance won't be as good as with a monitor attached directly. 3D gaming is definitely out of the question and video playback in anything other than standard definition will probably be choppy. Still, to put your email or Twitter app on a separate screen, as one example, they should suffice.

An alternative is to turn your iPad or iPhone into an external display.

iOS apps like Air Display or Duet let you turn your iPad and/or iPhone into an external display for your Mac, letting you add a third or even fourth screen in addition to the built-in display and external display(s) connected via DVI/HDMI/Mini-DisplayPort/Thunderbolt. Here's how to turn your iPad into a second display.

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