Connect the cable to your graphics port, then plug in power
Connecting a second monitor is straightforward: plug the video cable into the correct port on the back of your computer, then plug the monitor's power cable into an outlet. Your computer will usually detect the new monitor within a few seconds. Windows and macOS both have built-in settings to arrange how the monitors work together — whether they show the same image, extend your workspace, or display only on the second screen.
The hardest part is often finding the right port. Most computers have multiple video outputs, and using the wrong one means the monitor stays dark. The port you need depends on what your monitor cable is, what your computer has, and sometimes which graphics card is active.
Key Takeaways
- Match your monitor's cable type to a port on your computer — HDMI, DisplayPort, USB-C, or VGA are the most common.
- If your computer has both integrated graphics and a dedicated graphics card, plug into the card's ports, not the motherboard's.
- After plugging in, open display settings to choose whether monitors show the same image, extend your workspace, or show only the second screen.
- If the monitor stays dark, try a different port or restart your computer — Windows and macOS sometimes need a moment to recognize the connection.
Identify which video ports your computer has
Look at the back of your desktop computer or the sides of your laptop. You are looking for rectangular or trapezoidal ports labeled or shaped like HDMI, DisplayPort, USB-C, or VGA. Most modern computers have at least two of these. On a laptop, they are usually on the left or right edge. On a desktop, they are on the back panel, either on the motherboard itself or on a separate card sticking out from a slot.
HDMI is the most common. It is a flat rectangular port about the size of a USB port. DisplayPort looks similar but slightly different — the corners are beveled. USB-C is small and oval. VGA is a trapezoid with three rows of tiny holes and is older but still common on some monitors and projectors. If you see multiple ports of the same type, any of them will work for a second monitor.
On a laptop, check the manual or manufacturer's website if you cannot see the ports clearly. Some laptops have video ports only on one side, or only certain ports support external monitors.
Match your monitor cable to your computer's ports
Look at the cable attached to your monitor or the cable that came with it. The connector at the end tells you what type of port you need. If the monitor has a removable cable, you may have options — some monitors come with HDMI, DisplayPort, or USB-C cables, and you can buy adapters if your computer does not have the right port.
If your monitor cable is HDMI, plug it into any HDMI port on your computer. If it is DisplayPort, use a DisplayPort port. If it is USB-C, use a USB-C port that supports video — not all USB-C ports do, so check your computer's manual if you are unsure. VGA cables are older and less common on new computers, but if that is what you have, look for the trapezoid port.
If your monitor cable does not match any port on your computer, you will need an adapter. A USB-C to HDMI adapter, HDMI to DisplayPort adapter, or similar device can bridge the gap. These cost between $10 and $30 and are widely available. Make sure the adapter direction is correct — some only work one way.
Plug into the graphics card, not the motherboard, on a desktop
Desktop computers with a dedicated graphics card have video ports in two places: on the motherboard itself (near the bottom of the back panel) and on the graphics card (usually higher up). Always use the graphics card's ports for monitors. The motherboard's ports are disabled when a graphics card is installed, and plugging into them will not work.
If you are not sure whether your computer has a graphics card, look inside the case. A graphics card is a long board with a fan or heatsink, sticking out from a slot in the motherboard. If you see one, use its ports. If you do not see one, use the motherboard's ports — your computer is using integrated graphics built into the processor.
This matters because many people plug a second monitor into the motherboard by mistake and then think the connection is broken. The monitor will stay dark. Moving the cable to the graphics card's port fixes it when ready.
Turn on the monitor and check Windows or macOS settings
Plug the monitor's power cable into an outlet and press the power button on the monitor itself. Your computer should detect it within a few seconds. On Windows, right-click the desktop and select "Display settings." On a Mac, open System Settings, click "Displays," then "Arrangement." Both operating systems will show you the monitors connected and let you choose how they work together.
You have three main options. Extend means the second monitor shows a different part of your workspace — you can drag windows between them and move your mouse across both. Duplicate or Mirror means both monitors show the same image. Second display only turns off the first monitor and uses only the second one. Most people choose Extend because it gives you more screen space.
If the monitor does not appear in settings, try restarting your computer. Sometimes Windows or macOS takes a moment to recognize a new connection. If it still does not appear, try a different video port on your computer — you may have plugged into a port that is not active.
Arrange monitor positions if you are using Extend mode
When you have two monitors side by side, Windows and macOS need to know which one is on the left and which is on the right. If you set this wrong, moving your mouse to the right edge of the left monitor will not move it to the left edge of the right monitor — it will jump to the wrong place.
In Windows Display Settings, you will see two rectangles representing your monitors. Drag them so they match how your physical monitors are arranged. If your second monitor is to the right of your first, drag its rectangle to the right of the first one's rectangle. If it is above, drag it up. On a Mac, the Arrangement tab shows the same thing — drag the monitor icons to match your physical setup.
You can also set which monitor is your main display (where the taskbar or menu bar appears) and adjust the resolution and refresh rate of each monitor separately. Most people leave these at their default settings unless they notice the image looks blurry or the text is too small.
Troubleshoot if the second monitor stays dark
If you plugged everything in and the monitor is still dark, try these steps in order. First, make sure the monitor's power button is on and the power cable is plugged in — the monitor usually has a light on the front when it is powered. Second, try a different video port on your computer. Third, restart your computer. Fourth, check that you are using the graphics card's ports on a desktop, not the motherboard's.
If the monitor still does not work, the cable may be damaged or the port may be broken. Try the cable in a different computer if you have one available. If the cable works elsewhere, your computer's port is likely broken and you will need to use a different port or have the computer serviced. If the cable does not work elsewhere, the cable itself is damaged and you will need a replacement.
On a laptop, also check the manufacturer's website to confirm that the port you are using supports external monitors. Some laptops have USB-C ports that only charge or transfer data, not video. The manual will tell you which ports work for displays.
Frequently Asked Questions
Do I need a special cable to connect a second monitor?
No. Use whatever cable came with your monitor or buy a standard HDMI, DisplayPort, or USB-C cable that matches your monitor and computer. These are inexpensive and widely available. If your monitor and computer use different connector types, an adapter is cheaper than a new cable.
Can I use two different monitor brands at the same time?
Yes. You can mix any monitors as long as your computer has enough video ports and the cables match. Windows and macOS handle different monitors without any problem. You can even use different resolutions or refresh rates on each monitor.
Will a second monitor slow down my computer?
No. A second monitor uses very little processing power. Your computer may feel slower if you are running many programs at once, but that is not because of the monitor — it is because of the programs. The monitor itself is just a display.
What if my laptop only has USB-C ports?
USB-C can carry video, but not all USB-C ports on a laptop support it. Check your laptop's manual to see which ports work for displays. If none do, you will need a USB-C docking station that has HDMI or DisplayPort output. These typically cost $50 to $150.
Can I connect more than two monitors?
Yes, if your computer has enough video ports or if you use a docking station. Most desktop computers can handle three or four monitors. Laptops usually support one or two external monitors depending on the model. Check your computer's specifications or manual to see the limit.