Many users are faced with a situation where the main monitor is not enough for comfortable work or entertainment, and there is no opportunity or desire to buy new equipment. In this case, an excellent solution would be to use an old or additional laptop as a second screen. This not only saves your budget, but also allows you to expand your workspace without extra costs.
There are several proven methods for accomplishing this task, from built-in operating system functions to the use of specialized software. The specific method you choose depends on your operating system, the availability of required ports, and your image latency requirements. We will analyze each option in detail so that you can choose the most suitable one for your conditions.
Using built-in Windows tools to expand the screen
The Windows 10 and 11 operating system has a built-in function Projecting to this computer, which allows you to use a laptop as a signal receiver without installing additional software. This technology works through the Miracast protocol and requires Wi-Fi adapters on both devices. To activate the function, you need to go to the system parameters and enable the appropriate mode.
To configure the receiver, open Settings โ System โ Project to This PC. If you don't see the option, click the More Features link and install the Wireless Display feature. Once installed, you can choose which devices can connect to your laptop, from Always Off to Available Everywhere. It is recommended to select the "Available Everywhere" mode for the first connection.
- ๐ฅ๏ธ Make sure both devices are on the same Wi-Fi network for stable operation.
- ๐ A request for connection permission will appear on the receiving laptop, which must be confirmed.
- ๐ฎ This method is great for watching videos, but may have a slight lag when playing games.
On your main computer, press the key combination Win + P and select the "Expand" or "Duplicate" mode. The laptop screen will light up and you can drag windows between devices. It is important to note that for correct operation, Wi-Fi drivers on both devices must be updated to the latest versions.
โ ๏ธ Warning: The wireless connection is sensitive to interference. If you see image tearing or pixelation, try moving your devices closer to the router or switching to the 5 GHz frequency.
- Wireless (Wi-Fi)
- Wired (HDMI/USB)
- Via network (LAN)
- I don't know which one to choose
Connecting via HDMI cable using a capture card
If you need minimal latency and high picture stability, wireless methods may not be suitable. In this case, the most reliable solution is to use a video capture card. The point is that the port HDMI on most laptops it is an output, not an input, so you wonโt be able to directly connect two devices with a cable.
The solution to the problem lies in purchasing an inexpensive video capture card with a USB 3.0 interface and an HDMI connector. This device converts the video signal from the main computer into a digital stream, which the laptop can process as a webcam. The cost of such devices varies from budget Chinese models to professional solutions from AverMedia or Elgato.
- ๐ Connect the capture card to the USB port of your laptop, which will work as a monitor.
- ๐บ Insert the HDMI cable into the output of the main PC and into the input of the capture card.
- ๐น Launch the Camera app or OBS Studio on your laptop to display the signal.
A new monitor will appear in the main computer settings in the โDisplayโ section, which you can configure through the menu Settings โ System โ Display. This method allows you to use the laptop even without access to the Internet and does not load the processor with wireless modules. Image quality will depend on the USB port bandwidth and capture card model.
โ๏ธ Required components for HDMI connection
Can I use an old monitor instead of a laptop?
Yes, any monitor with an HDMI input can be connected directly to a PC. A laptop requires an intermediate device, since its connector is usually a signal output, not an input.
Using third-party software solutions over a local network
For advanced users who require low latency and cross-platform compatibility, dedicated utilities are great. Programs like Spacedesk or Deskreen use the TCP/IP protocol to transmit the video stream. They allow you to turn any gadget with a browser or client installed into a second display.
Unlike the built-in Windows tools, these applications often provide more settings, such as choosing the refresh rate, color depth, and stream compression. This is critical for Spacedesk, which supports operation via Wi-Fi and Ethernet. To work, you need to install the server part on the main PC and the client part on the laptop monitor.
| Program | Connection type | Compatibility | Features |
|---|---|---|---|
| Spacedesk | Wi-Fi / LAN | Windows, Android, iOS | Free, low latency |
| Deskreen | Wi-Fi / LAN | Any OS with a browser | Works via web interface |
| TeamViewer | Internet | All platforms | Screen duplication, not extension |
| Synergy | Local network | Windows, macOS, Linux | General mouse and keyboard controls |
After installing both components, start the server on the main computer and enter the IP address or hostname in the client on the laptop. If the connection fails, check your firewall settings, as it may be blocking incoming connections to the ports used by the program. It is often necessary to add an exception for the executable file in the security settings.
โ ๏ธ Attention: When using programs over Wi-Fi, make sure that the router supports the 802.11ac standard or later, otherwise there may be severe delays and disconnections when moving the mouse.
USB-C connection with DisplayPort Alt Mode support
Modern laptops, especially those with 10th generation Intel Core processors or later or MacBooks, often come with ports USB-C with video support. If your laptop has such a port, you can use it to connect to another device, but it is important to understand the direction of the signal. Usually this port is also an output, but there are docking stations and hubs that can operate in video input mode.
A more common scenario is to use a laptop as your primary computer and another device as a second screen via USB-C. However, if the goal is to turn a laptop into a monitor, you will need an active converter or a special cable that supports video signal transmission in both directions, which is extremely rare in domestic conditions.
- ๐ Check your USB-C port specification for a lightning bolt or monitor icon.
- ๐ Use USB-C to HDMI adapters with Video In function if available.
- โก Make sure that the power supply is connected, as transmitting the video signal requires energy.
Unfortunately, most standard USB-C cables are only designed for data transfer and charging, not video reception. Unlike HDMI, there is no universal all-in-one solution. Without a special video capture card with a USB-C input, it is almost impossible to turn a laptop into a monitor through this port. Therefore, this method often comes down to the need to purchase specific equipment.
Before purchasing an adapter, be sure to check the port specifications on both devices. Not all USB-C ports support video output or video input, even if the device has one.
Set up screen sharing on macOS
Apple ecosystem users have access to the feature Sidecar, which lets you use an iPad or another Mac as a second display. If you have a laptop MacBook, which you want to turn into a monitor for another Mac, this can be done through Presentation mode or third-party utilities, since the native Sidecar only works with iPad.
To implement the task between two Macs, you can use the software Luna Display or Duet Display. These apps create a virtual display by streaming images over Wi-Fi or a Thunderbolt to USB cable. This ensures high smoothness and no lag, which is critical for working with graphics and design.
- ๐ Both devices must be authorized under the same Apple ID.
- ๐ Enable two-factor authentication to secure your connection.
- ๐ถ Use a Thunderbolt cable for maximum data transfer speeds.
In settings System Settings โ Displays you will be able to select the โExpandโ or โDuplicateโ mode. The system will automatically adjust the resolution and scaling to the laptop screen. It is important to note that Duet Display requires the application to be installed on both devices and to have the latest version of macOS.
Using Apple's native ecosystem provides the most seamless experience, but requires compatible hardware and licensed software.
Technical nuances and troubleshooting common problems
When trying to connect a laptop as a monitor, problems often arise with screen resolution or lack of sound. The system may detect the second display, but display the image in poor quality or in the wrong aspect ratio. This is due to the settings of the video card drivers on the main computer.
Go to your video card's control panel - NVIDIA Control Panel or AMD Radeon Settings. Find the Display section and make sure the second screen is set to the correct resolution, e.g. 1920ร1080 at frequency 60 Hz. Also check if the output device's audio is enabled, as it may remain on the main monitor by default.
- ๐ Select your laptop from the Windows playback device list.
- ๐จ Calibrate the colors, as laptop matrices may differ from the main monitor.
- ๐ Update the chipset and video controller drivers on both devices.
If the image flickers or disappears, try lowering the refresh rate or changing the data encoding. If you use software solutions, check the load on the processor and network adapter. High network load can lead to packet loss and screen artifacts.
โ ๏ธ Attention: Incorrectly configured resolution may result in the picture not fitting on the laptop screen or being greatly stretched, which will worsen the perception of text and interface.
What to do if the laptop does not see the second monitor?
Check the physical cable connections, make sure the drivers are up to date, and try reconnecting the device after restarting both computers.
Frequently asked questions and answers
Is it possible to connect a laptop to another laptop via HDMI directly?
No, in most cases this is not possible, since HDMI ports on laptops are Output, not Input. To connect, you will need a video capture card.
Is there a delay when using a wireless connection?
Yes, wireless methods (Wi-Fi) always have a slight delay (lag), which can be noticeable in fast-paced games, but is almost unnoticeable when working with documents or watching videos.
Which method is the cheapest?
The cheapest way is to use Windows' built-in Project to This PC feature, or free programs like Spacedesk if you already have a router and devices on the same network.
Can an old laptop be used as a TV?
Yes, if you connect a TV set-top box to it via HDMI and use a video capture card, or use a laptop with a Smart TV application installed, if it is connected to the Internet.
What is the minimum hardware requirement?
Both laptops must have at least a mid-range processor and 4 GB of RAM, as well as a modern Wi-Fi adapter for stable operation of wireless methods.