Many households quietly accumulate retired laptops, and a new guide suggests one of them might find a second life as an extra screen for the machine still in daily use. The approach asks little of the owner: no purchase, only attention to which operating systems are involved and whether the link will run through the air or through a cable. In that choice lies the familiar tension between convenience and immediacy, since wireless links are easy to set up but carry a small delay, while a wired capture card is more work but responds more faithfully to the hand that moves the cursor.
How to Turn a Spare Laptop Into a Second Monitor on Windows, Mac, Linux, or Via HDMI
A spare laptop can become a free second monitor
Mark
So the pitch is that an old laptop becomes a free second monitor. How free is it really?
Mimi
Free if you stay wireless. On Windows it's built in through Miracast, and on Macs it's AirPlay. Deskreen is free too, though extending with it needs a cheap dummy plug.
Luke
So 'free' has an asterisk. The dummy plug and the capture card both cost something, and the guide doesn't give prices beyond calling the plug cheap.
Mark
Why not just run an HDMI cable between the two laptops?
Mimi
Most laptop HDMI ports only send video out. They can't receive, so a cable alone does nothing. That's why the capture card exists.
Mark
What does the card actually do?
Mimi
It shows up as a webcam. You view your main screen's feed in a camera app or OBS Studio.
Luke
Worth noting that makes it a video feed, not a true extended desktop. The guide describes viewing the feed, and doesn't say it extends the display the way Miracast does.
Mark
And lag?
Mimi
Wi-Fi methods can lag, so they suit presentations or tabs. The wired route has less, and the guide says it won't bother anyone but competitive gamers.
Luke
Those lag claims are general. No measurements are given, so how much delay you'll see is unknown.
Der Puls
- A spare laptop gathering dust in a drawer becomes the answer to a cramped desktop.
- Mismatched operating systems create friction, forcing users toward extra software or hardware.
- Wi-Fi casting through Miracast or AirPlay offers a quick route, though a slight lag follows every movement.
- Gamers and latency-sensitive users are steered toward an HDMI-to-USB capture card, where delay shrinks and the setup becomes wired and steady.
Many households quietly accumulate retired laptops, and a new guide suggests one of them might find a second life as an extra screen for the machine still in daily use. The approach asks little of the owner: no purchase, only attention to which operating systems are involved and whether the link will run through the air or through a cable. In that choice lies the familiar tension between convenience and immediacy, since wireless links are easy to set up but carry a small delay, while a wired capture card is more work but responds more faithfully to the hand that moves the cursor.
Somewhere in a closet or desk drawer sits a laptop nobody uses anymore. Engadget's latest how-to suggests it could become a second monitor for your main computer, at no cost and without buying anything new.
The reason is easy to feel. A second screen gives room for tabs, presentations, and tasks running side by side. Mirroring shows the same desktop on both displays, while extending spreads one desktop across them. Getting there, though, depends on compatibility, on choosing between wired and wireless, and on a few settings.
Two Windows machines can use the built-in Miracast feature, enabled through Wireless Display and connected by a PIN over Wi-Fi. Two Macs can use AirPlay, provided the secondary MacBook is from 2018 or later and both share an Apple ID. Mixed systems need software such as Deskreen, a free tool that links devices through a QR code and a browser, though extending the desktop requires a cheap dummy plug. Each wireless path brings some lag.
For the most responsive result, the guide turns to a wired route. Because most laptop HDMI ports only send video out, an HDMI-to-USB capture card is needed, which lets the spare laptop read the feed like a webcam. The same method can carry a PlayStation or Switch, with less delay than wireless options.
The practical lesson is to match the method to the task: wireless for presentations and tab overflow, the capture card when smooth response matters most.
Somewhere in a closet or desk drawer, there is probably a laptop that nobody uses anymore. Engadget's latest how-to guide makes the case that this machine can become a second monitor for your main computer at no cost, with no new hardware purchase required.
The appeal is simple. Whether you are gaming, working or just browsing, a second screen adds room. Mirroring puts the same desktop on both displays, which is useful for presentations. Extending spreads one desktop across both screens, so you can keep more tabs visible and juggle tasks more easily. The catch, according to the guide, is that the job is not as simple as plugging in an HDMI cable. You need to check compatibility, choose between wired and wireless, and adjust some settings.
If both machines run Windows 10 or 11, the built-in tool is Miracast, which connects devices over Wi-Fi. On the spare laptop, open Settings, then System, then Projecting to this PC. Choose Optional features, then View features, and add Wireless Display. When it installs, go back to the same page, set it to Available everywhere, and open the Wireless Display app. On the main computer, press the Windows key plus K, pick the spare laptop from the list, enter the PIN and allow keyboard and mouse input. You can then duplicate or extend the screen, and switch between them with Windows key plus P. Both machines need Wi-Fi, and some lag is possible, so the guide calls it good for presentations or large numbers of tabs but not ideal for gaming.
Two Macs can use AirPlay, provided the MacBook acting as the second screen is from 2018 or later. On that laptop, open System Settings, then General, then AirDrop & Continuity, turn on AirPlay Receiver, and under Allow AirPlay for choose Current User. Both MacBooks should be signed into the same Apple ID. On the primary Mac, open System Settings, then Displays, click the plus sign in the dropdown, and select the secondary device. Mirroring or extended display is chosen in settings. Like Miracast, AirPlay runs over Wi-Fi and can introduce a slight delay.
Mixed setups, such as a Windows PC with a MacBook or anything involving Linux, call for software. The guide points to Deskreen, a free, open-source tool that works over Wi-Fi. Both computers must be on the same network. Download Deskreen on the main device, and it produces a QR code and a URL. Open either one in the spare laptop's browser to link the two. Deskreen mirrors by default. To extend the desktop instead, you need a cheap virtual display adaptor, sometimes called a dummy plug, inserted in the main computer's HDMI port. As with the other methods, Wi-Fi means lag.
For a wired connection, there is a wrinkle: most laptop HDMI ports only send video out, so a plain cable between two laptops will not mirror or extend anything. The workaround is an HDMI-to-USB video capture card. Connect the main device's HDMI cable to the card, then plug the card's USB end into the spare laptop. The card behaves like a webcam, so you can watch the feed in the camera app or in OBS Studio, a free video program that runs on Windows, Mac and Linux.
The same trick works for consoles. A PlayStation or Nintendo Switch can be connected to the laptop this way, letting you play without a TV. Some lag remains, but usually less than over Wi-Fi, and the guide says it is unlikely to matter unless you play competitively. If a second screen does not appeal at all, the guide offers one last idea: turn the old laptop into a smart home hub.
The practical takeaway is to match the method to the task. Wireless options are fine for presentations and tab overflow, while the capture card is the better route when smooth response matters.
Bemerkenswerte Zitate
Wi-Fi-based methods may lag, making them fine for presentations but not ideal for gaming.— Engadget guide
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