Laptop — If your laptop has at least one video output port, you can use it to connect a second monitor. Desktop — Your desktop computer must have at least two video ports in total (one to connect the primary monitor and one to connect the second monitor). The ports do not have to match, but they do have to be a part of the same graphics card; this means that if you have two graphics cards installed, you’ll need to use the same one for both monitors.
HDMI — Resembles a six-sided, flat port. DisplayPort — Resembles a rectangular port with a crimped side. USB-C — Resembles a thin, rounded oval port. VGA — Resembles a colored trapezoid with pinholes in it. VGA isn’t common on post-2012 computers, but you may have to work with VGA if you’re connecting a new computer to an old monitor (or vice versa).
If you have an exceptionally old monitor, you may find a DVI port on the back of your second monitor. DVI ports resemble white boxes with clusters of holes, as well as a section with a few separate holes.
If your computer and your monitor both have a common port (e. g. , HDMI), it’s easier (and cheaper) to buy a cable that fits both ports even if a higher-definition option is available. If the monitor’s input doesn’t match your computer’s output (e. g. , if the monitor uses a VGA input while your computer uses an HDMI output), you will need to buy an adapter. Some video output combinations, such as HDMI to DisplayPort, come as cables that you can purchase instead of buying an adapter.
Remember, if you’re using a desktop computer, this must be a video output port that is part of the same graphics card that your primary monitor uses.
If you’re using an adapter, you’ll plug one end of the cable into the adapter and then plug the monitor’s cable into both the monitor and the adapter.
Depending on your computer, you may see your desktop reflected on the second monitor when it turns on.
Duplicate these displays — Copies everything that’s on your computer’s primary display to the second monitor. Extend these displays — Creates an extension of your desktop on the second monitor. This essentially gives you more space with which to work. Show only on 1 — Blacks out the second monitor and shows content only on the first monitor. Show only on 2 — Blacks out the first monitor and shows content only on the second monitor. Depending on your computer, you may have additional options here.
USB-C (Thunderbolt 3) — Oval-shaped port. Modern MacBooks, MacBook Pros, and iMacs have anywhere from one to four of these. Thunderbolt 2 — Square-shaped port. Found on older Macs. HDMI — Six-sided, flat port. Found on older Macs.
If you have an exceptionally old monitor, you may find a DVI port on the back of your second monitor. DVI ports resemble white boxes with clusters of holes, as well as a section with a few separate holes.
If your computer and your monitor both have a common port (e. g. , HDMI), it’s easier (and cheaper) to buy a cable that fits both ports even if a higher-definition option is available. If the monitor’s input doesn’t match your computer’s output (e. g. , if the monitor uses a VGA input while your computer uses an HDMI output), you will need to buy an adapter. Some video output combinations, such as HDMI to DisplayPort, come as cables that you can purchase instead of buying an adapter.
If you’re using an adapter, you’ll plug one end of the cable into the adapter and then plug the monitor’s cable into both the monitor and the adapter.
Depending on your computer, you may see your desktop reflected on the second monitor when it turns on.
If you just want your second monitor to mirror whatever is on your Mac’s primary monitor, skip this step.
