How to connect a second display to a Mac ?.


Your Mac screen is not enough for you ? Good news, it is possible to connect a second screen.

In this tutorial, we explain how to identify the adapter to connect your Mac to another screen and how to set up your computer so that it detects it.

Note that since the launch of the Sierra in September 2016, it would seem that some adapters third party no longer work with the Mac.

Identify the ports on your Mac.

The choice of the adapter depends the model of your Mac and its ports. Here are the two main connection ports of the Mac.

If your Mac model was released at the end of 2008, so it is equipped with the Mini DisplayPort, using the appropriate adapter, you can connect compatible devices with VGA, DVI and HDMI.

Mini Display Port

If your Mac is released in 2011 and it is equipped with the Thunderbolt port. If it came out after 2013, so it has the Thunderbolt 2.

Thunderbolt port

On the other hand if you have an iMac or a Macbook Pro dating from 2016 or later, then you have a USB port-C. The latter does not allow you to use the adapters, Mini DisplayPort to dual-link DVI, Mini DisplayPort to DVI adapter, Mini DisplayPort to VGA adapter and LED Cinema Display.

USB port‑C (Thunderbolt 3)

Identify the ports on your external screen.

Now, we need to identify the outputs of your second screen to find the adapter that can be connected to it.

The port VGA 15 pins on 3 rows. It allows you to see videos in HD with an analog audio signal.

The output DVI (24-pin) offers a much better display quality than VGA, the colors will be more nuanced. The difference is noticeable when you watch a video in HD.

Depending on whether it is a DVI-a in DVI-D or DVI-I, the signals transmitted and the number of pins will not be the same.

Port HDMI (High-Definition Multimedia Interface) is compatible with not less than 8 channels of audio and it is the most widespread on television. Its new standard (HDMI 2.1) has a bandwidth of 48 Gbits/s.

What cable to choose ?.

There are 5 different cables to connect your Mac to an external monitor. You can buy one from a third party seller where it will be without doubt less expensive.

However, as has been mentioned above, some became obsolete with macOS Sierra. In order not to run the risk of incompatibility, it is better to buy a cable of the Apple brand.

Also, note that the ports on Apple computers are female, your cable should have outputs males.

Below you will find the different adapters that you can use.

The Thunderbolt 3 (USB-C) to Thundebolt 2 (59 €) is used to connect screens that have a Thunderbolt port.

The USB-C Digital AV multiport (79 €) allows you to connect your Mac to a projector or VGA display.
Be aware that it is not compatible with the content with HDCP (High-Bandwidth Digital Content Protection). This standard provides the copy protection of audio streams and digital. You will need an output and an HDMI cable.

The Mini DisplayPort to VGA adapter (35 €) for the VGA monitors to the Mac with a port to Mini Display or Thunderbolt.

The Mini DisplayPort to DVI (35 €) can be used to connect a DVI monitor to a Mac with ports, Mini Display or Thunderbolt.
DVI is compatible with HDCP. It is suitable for screens that are incompatible with the resolutions of Dual Link DVI (1920 x 1200 or lower).

The Mini DisplayPort to dual-link DVI (119 €) is intended for screens DVI with resolutions of a minimum of 1920 x 1200. To use it, your Mac must have a USB port..

Set up a second screen to your Mac.

Connect the adapter to your Mac.

Open System Preferences → Monitors.

Click on the tab Available.

Do not check the box video Mirroring, unless you want to see the same content on your computer.

Drag the monitors into the desired position. A white menu bar appears, it serves to indicate the main screen. Slide on the screen of your choice.


To copy the video on both screens, follow the points 1 to 4 given above and check the box for video Mirroring.

You can also select Display options for video mirroring in the menu bar. A status will be displayed in the menu bar, from which you can enable and disable the second screen.

If you have an Apple TV, you can use AirPlay as a 2nd screen to display your TV.

Problems with the display.

We have listed below the display problems that are most common and their solutions.

If the cables and the outputs match but your screen stays black, try to restart your Mac.

If after the previous attempt, nothing works then restart your computer in safe mode and restore the default display settings.

You can also try to adjust the brightness and contrast. To do this go to system Preferences → Monitors, and change the resolution.

If your Mac does not seem to detect the external monitor, then go to System Preferences → Monitors. Press Alt, and then click on the tab Detect displays.