How to use your laptop as a second monitor

Whether you’re gaming, working or just surfing the web, adding a second monitor is one of the best ways to upgrade your workflow. Display mirroring, which shows the same desktop on both screens, can be handy for presentations, while extending the display gives you a wider desktop. Extending the desktop and additional screen space means more visible tabs, easier multitasking and more productivity. But making this change doesn’t necessarily require buying a fancy setup. If you have a spare laptop lying around at home, you can make some small tweaks to use dual monitors without going all-in on new hardware.

Turning your laptop into a second screen is pretty easy but not necessarily as easy as plugging in an HDMI cable. First, you need to check your computer’s compatibility, consider wired versus wireless options, and adjust some settings on your system to smoothly extend or mirror the display. So how, exactly, do you turn your laptop into a second monitor? Here are the steps for Windows, Mac and Linux, as well as wired options via HDMI connections.

If both your primary computer and the spare laptop you want to use as a second monitor are running Windows 10 or 11, extending or mirroring them is very easy thanks to the operating systems’ built-in wireless casting tools. These rely on Miracast, a functionality that enables connections between devices via Wi-Fi and only requires a quick workflow to set up.

To activate it, go to your replacement laptop, open it Settingsthen Systemthen Projection on this PC. Click Optional featuresthen View featuresthen select Wireless display to be added. Once it is installed, go back to the same page and install it Available everywhereand open the Wireless Display app.

Now you are ready to mirror or extend your display. On your main computer, press the Windows key + K, select the replacement laptop from the list of available displays, enter the PIN and allow keyboard and mouse input. You can then choose to duplicate or extend your screen, and you can switch at any time with Windows key + P. Remember, this method of connecting your devices requires Wi-Fi on both machines, and you may experience some lag. Therefore, although it is great for organizing presentations or a large number of tabs, it may not be the best choice for gaming.

If both of your devices are Macs, you can use AirPlay to connect the two, but only if the MacBook is from 2018 or later. Once you’ve confirmed that your device is compatible, open the MacBook you want to use as a second screen System settingsselect Generalthen AirDrop & Continuity. Open up AirPlay receiver and then under Enable AirPlay forselect Current user. Make sure both MacBooks are signed into the same Apple ID to ensure a smooth connection. On your primary device, open System settingsthen Displayed and click the plus sign from the drop-down menu to select your secondary device from the list. Decide whether you want mirroring or extended display, which can be selected under settings. Like Windows Miracast, Apple’s AirPlay works over Wi-Fi and thus may have a slight delay. For a cable option with less lag, see the HDMI section below.

When connecting between two different operating systems, whether between a Windows PC and a MacBook or anything involving Linux, you need software like Deskreen, a free open-source tool that runs on Wi-Fi. To connect, make sure that both computers are on the same Wi-Fi network, and download Descreen on the main device. Descreen offers a QR code and URL. Open this in the spare laptop’s browser to connect the devices. Descreen mirrors the display by default. To extend to the spare laptop, you need a cheap virtual display adapter, or a “dummy plug”, in the HDMI port of your main computer. Like the other systems, any software that connects devices via Wi-Fi will have some lag, so consider the wired option below for gaming or other activities that rely on smoother connections.

Most laptop HDMI ports are video-out only, so connecting two devices together with one cable doesn’t allow you to directly extend or mirror displays. To get around this, get an HDMI-to-USB video capture card that can be plugged into both laptops. Plug the HDMI cable from your main device into the card, then plug the USB end of the card into the replacement laptop. The capture card works as a webcam, so you can view the feed in your laptop’s camera app or a free video app like OBS Studio, which runs on Windows, Mac, and Linux.

If you play games and want to play a console without a TV, you can connect a PlayStation or a Nintendo Switch to the laptop in the same way. Again, there may be a small amount of lag but usually less than Wi-Fi-based connections, and it’s unlikely to catch you out unless you’re a competitive gamer. If none of these applications appeal to you, you can always use your old laptop to make a smart home hub.