How to check a laptop and external monitor together

Your external monitor is connected, but the picture looks wrong, the screen is blank, or you are not sure the laptop sees both displays. Check the displays together before changing settings at random.

The Screens tool lists connected screens with their resolution and scale, and lets you run a color test on each one. Use it to check what the browser can see, then confirm the display mode in your computer's settings.

Check both screens

1. Connect the monitor to your laptop, turn it on, and select the correct input on the monitor, such as HDMI or USB-C.
2. Open the Screens tool. Check that the list includes both the laptop screen and the external monitor. If you connected the monitor after opening the tool, reload the page and check again.
3. Compare the resolution and scale shown for each screen with the settings on your laptop. These values can differ between the built-in display and the external monitor.
4. Run the color test on each listed screen. Look for missing colors, unexpected tint, flickering, or parts of the test that do not appear correctly. Move your browser window to the other display before checking it if needed.

Keep the monitor's on-screen menu available while you test. If the monitor says there is no signal, the issue is probably the connection or selected input, rather than the colors shown by the browser.

What the result means

Both screens appear and the color test looks normal

The laptop and browser can see both displays, and the basic image output is working. If a particular app still opens on the wrong screen or looks too large, check the display arrangement, resolution, and scale in your operating system settings.

Only the laptop screen appears

The external monitor may not be detected, or the laptop may be set to use only its built-in display. Check the cable and monitor input, then look for the monitor in the system's display settings. Some USB-C ports transfer data and power but do not support video, so check your laptop's port specifications if a USB-C connection never produces a picture.

Both screens appear, but one looks blurry or unusually large

The display may be using a resolution that does not match its panel, or its scale may make menus and text larger. Resolution controls image detail. Scale changes the size of text and interface elements, not the display's physical pixel count.

The test appears on both screens, but one has bad colors or flickers

Check that screen using its own built-in menu, if available. If its menu also looks tinted or flickers, the monitor, cable, adapter, or power supply may be at fault. If the monitor menu looks normal but the browser test does not, check the computer's display settings and graphics software.

How to fix a missing or incorrect display

1. Check the monitor's input. Use its physical controls to choose the input that matches the cable. A monitor set to DisplayPort will show no picture from a laptop connected over HDMI.
2. Reconnect the cable. Unplug it at both ends and connect it firmly again. If you use a dock or adapter, connect the monitor directly to the laptop if possible, or try another port and cable.
3. Choose the right display mode. On Windows 11, open Settings › System › Display, select the external display, and choose Extend these displays or Duplicate these displays under the multiple display options. On macOS, open System Settings › Displays and set the external screen to an extended display instead of mirroring if you want separate desktop space.
4. Ask the computer to detect the screen. In Windows 11, open Settings › System › Display, expand the multiple display options, and select Detect. On a Mac, disconnect and reconnect the display, then check System Settings › Displays again.
5. Set a supported resolution. In Windows 11, select the display in Settings › System › Display and choose a resolution marked Recommended. On macOS, open System Settings › Displays and choose a resolution option that gives a clear picture without making the interface too small.
6. Restart the graphics connection. Restart the laptop with the monitor connected. If the display still disappears, install operating system updates and check for graphics driver updates from your laptop maker.

When the monitor or cable may be faulty

Test the external monitor with another computer, and test the laptop with another monitor or TV. If the same monitor shows no signal from multiple devices, try another cable and input before arranging a repair. If it still fails, the monitor may need service.

If other displays work with the laptop but one port does not, the laptop's port or its video output may be damaged. A dock or adapter can also fail even when it still charges the laptop. Check warranty coverage before paying for a repair, especially if the problem started after a drop or liquid spill.

Extend and mirror are different

Extend gives you one desktop spread across two screens. You can move windows between them, and the screens can have different resolutions and scales. Duplicate, also called mirroring, shows the same image on both screens. This can be useful for a presentation, but the picture may be limited by the resolution both displays support.

If you extend the desktop, arrange the display rectangles in system settings to match where the screens sit on your desk. This makes the pointer move naturally from one screen to the other. For more detail about the resolution values, see how to check each connected screen's resolution.

The Screens check runs in your browser, with nothing to install.