TheTest.com

External Display Setup

How to connect an external monitor, adjust resolution and refresh rate, and arrange multiple displays

Connecting an external monitor usually just works — plug it in, and your desktop extends. When it doesn't, the issue is almost always the cable, a detection hiccup, or a resolution/scaling mismatch. Test your display at thetest.com/display to verify resolution and color accuracy.

Run the Display Test
  1. Connect your monitor using USB-C/Thunderbolt, HDMI, or a compatible adapter — the display should be detected automatically
  2. Open System Settings > Displays to see all connected displays listed with thumbnails
  3. Click Arrange to drag the display rectangles into position matching your physical setup — the cursor moves between screens based on this layout
  4. To set your main display, select a monitor and choose Use as main display — the menu bar and Dock move to that screen
  5. To change resolution, click a display thumbnail and select from the available options. Choose Default for display for the native resolution, or pick a scaled option for larger or smaller UI
  6. To change refresh rate, click the display thumbnail and select from the Refresh Rate dropdown (available when the display supports multiple rates, like 60Hz and 120Hz)
  7. To mirror instead of extend, right-click a display in the list and select Mirror — note that macOS uses the lower resolution of the two, which may make the higher-res display look softer
  8. For clamshell mode (using only the external display with the MacBook lid closed), connect the external display and a power source, then close the lid. The Mac stays awake and drives the external display. An external keyboard and mouse (or trackpad) are required
  9. If your display is not detected, open System Settings > Displays, hold Option, and click the Detect Displays button that appears. Also try unplugging the cable and plugging it back in, or restarting your Mac

Frequently Asked Questions

Why isn't my external monitor detected?▾

Start with the cable — try a different cable or port. If you are using an adapter (like USB-C to HDMI), make sure it supports video output. Restart your computer with the monitor connected. On Mac, hold Option in Display settings and click Detect Displays. On Windows, click Detect in Display settings. If nothing works, test the monitor with another computer to rule out a hardware issue with the display itself.

What cable do I need for my external monitor?▾

It depends on your ports. USB-C/Thunderbolt is the most common on modern laptops and carries video, data, and power over one cable. HDMI is the most universal and works for most monitors and TVs. DisplayPort is common on desktop monitors and supports higher refresh rates. If your laptop only has USB-C and your monitor only has HDMI, use a USB-C to HDMI adapter or cable. For 4K at 60Hz or higher, make sure your cable and adapter support the required bandwidth (HDMI 2.0+ or DisplayPort 1.2+).

Why does text look blurry on my external monitor?▾

This is almost always a scaling issue. If your monitor runs at a non-native resolution, everything looks soft. Set the resolution to the monitor's native resolution (the one labeled "Recommended" on Windows or "Default for display" on Mac). If the native resolution makes things too small, use display scaling (125% or 150% on Windows, scaled options on Mac) instead of lowering the resolution — scaling keeps text sharp while making UI elements larger.