How to Fix It When a Second Monitor is Not Working

Get your second display up and running right

A woman types at a Bloomberg terminal with eight monitors.

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Second monitors are a crucial tool for improving your productivity. Provided your computer can support multiple monitors, buying a second monitor is a good choice for enhancing your daily grind, but what do you do if your new second monitor is not detected?

Common Second Monitor Problems

Second monitor troubles appear in a few common ways:

  • The second monitor does not display any content and shows a black screen.
  • The second monitor displays content at a non-native resolution.
  • The content on the second monitor suffers from artifacts not seen on the primary monitor.
  • The display is distorted, discolored, duplicated, or otherwise "wrong."

Fortunately, the troubleshooting steps for most of these second monitor problems are essentially the same. By carefully following the steps below, you can diagnose and fix the exact cause of your second monitor malfunctions.

Causes of Second Monitor Problems

Regardless of the exact problem you experience, there are a few basic root causes of all second monitor problems:

  • Your computer cannot support the display, whether in color depth, pixel count, or interface options.
  • The monitor's cable is damaged or malfunctioning.
  • The computer's display drivers are not properly handling the secondary display.

How to Fix Second Monitor Problems on Windows and macOS

  1. Restart your computer. Restarting your PC is a classic troubleshooting step because it works so effectively. Not only can it solve the problem. It also closes other processes that might interfere. With a quick restart, you begin from a clean slate.

  2. If your second monitor is showing an image, but the image is blurry, pixelated, distorted, discolored, or a duplicate of your primary display, check your computer's display settings. If the frame rate or resolution is incorrect, the fix can be found in the same place. These display issues can be fixed on macOS and and you can easily change the resolution on Windows.

  3. Adjust scaling settings. If your windows display as different sizes on different monitors in Windows 10, you may need to adjust scaling settings. Go to Settings > System > Display or right-click the Desktop, then select Display Settings. Adjust the Change the size of text, apps, or other items slider. The recommended setting will match the apparent window size across monitors as closely as possible.

    On macOS, navigate to System Preferences > Displays. Click Default for display or click Scaled and choose the correct resolution.

  4. If your computer's settings do not fix the problem, use a hardware calibration device or adjust the monitor's color settings, its gamma, and brightness settings in the monitor's on-screen menu. Every monitor is different, but "Color" or "Display Depth" are reliable keywords to scan for.

    Some color issues can be the result of different display panels, backlights, technologies, and even age. If you need an exact match, consider professional-grade photo editing monitors.

  5. Fix your monitor's refresh rate using Windows' refresh rate settings.

    In macOS, navigate to System Preferences > Displays and adjust the Refresh Rate dropdown menu.

  6. Swap out the current cable. If you're seeing artifacts on your display or no picture at all, a bad cable is the most common culprit. Very long or poorly-shielded cables are especially prone to interference.

    Good cables don't need to cost a fortune. Gold-plated connectors or oxygen-free copper won't provide a noticeable difference in image quality, but poorly constructed cables can easily lead to issues. Be sure you're purchasing a cable from a trusted manufacturer. Monoprice offers an excellent combination of affordability and reliable quality.

  7. Connect the second monitor's cable to an alternate port. You can change the port on your PC, the port on your display, or both. Only change one at a time, so you can pinpoint which of the ports are causing the problem, if any. If your PC doesn't have a second compatible port, try connecting the monitor to a different computer. This can identify issues with your computer's settings or ports.

  8. Make sure your cable supports the correct version of your display standard. HDMI cables can support anything from HDMI 1.0, which provides only the most minimal support, to HDMI 2.1, which can support the highest resolutions, color spaces, and audio channels.

    USB-C and Thunderbolt monitors are even more confusing since the cables are physically interchangeable but not cross-compatible. DVI, meanwhile, has multiple versions, and it's entirely possible to plug an incompatible DVI cable into your computer or monitor.

    Look at any documentation that came with the cable or the website you purchased the cable from to learn the latest display connection version supported by your cable. If the cable doesn't support your display, you'll need to replace it with a cable that does. Additionally, check the physical appearance of the cable's connectors and the connectors on your PC and monitor to ensure they're the same.

  9. Remove any switches or converters from the signal chain. If your cable has HDMI on one end and DVI on the other, try a cable that has the same connector on both ends. If possible, remove or replace dongles and switches temporarily. If the simpler connection works, the removed device is to blame. Be sure to only remove one device at a time for proper troubleshooting.

  10. Try a different display interface. For example, if your second monitor is currently connected over HDMI, try using Display Port instead. This can accomplish a few things. If the current interface can't drive all the pixels in your second monitor, switching to a different interface can fix that problem.

    Based on capability, you can rank common display connectors like so: DisplayPort, HDMI, DVI, Thunderbolt, USB-C, VGA. Unless you must use a VGA connection for legacy compatibility, avoid it, as it cannot properly drive modern displays. Don't forget there are multiple versions of HDMI, DVI, and USB-C. Just because you can plug a cable into a port doesn't mean you'll have full compatibility.

  11. Update your computer's display drivers. If you have a third-party discrete graphics card, you can update the drivers from the manufacturer. If you're plugging your monitor directly into the motherboard's display connectors, visit the motherboard or computer manufacturer's webpage to see if there are any updated drivers for those features. On Windows, check for updated drivers for your connected displays.

  12. Lower the image quality. If your monitor is suffering poor frame rate, choppiness, or corrupted video or game content, reducing the complexity of the signal can help. For games, try the lowest-quality settings first, then gradually improve the quality until the issues reappear. For video content, try a lower resolution or a less-demanding frame rate.

  13. Check your power connections. If your monitor won't turn on, try different power connectors or wall outlets. Test wall outlets with other devices before plugging in your monitor to ensure they work properly.

  14. Check your monitor's input settings. If your monitor has multiple input interfaces, make sure you have the correct one selected in the monitor's on-screen menu. Most monitors have an auto-detect feature that automatically switches to the connector receiving signal, but that doesn't always work. Try setting the display connector manually.

  15. Make sure your monitor can display the content you're sending it. Does your monitor have sufficient color gamut, resolution, or bit depth to display the content properly? Consult your monitor's documentation or the monitor manufacturer's website.

  16. If none of these steps fix your problem, you may need to replace your monitor. If you see colored lines, black or colored points, or cracks in the image, your monitor's panel may be damaged, which will require replacement.