How to Use Another Laptop as a Second Monitor

Having a second screen can transform how you work — but buying a dedicated external monitor isn't always practical or necessary. If you have a spare laptop sitting around, there's a good chance you can put it to work as an extended display. Here's what that actually involves, and what determines whether it works smoothly for your setup.

Why Use a Second Laptop as a Monitor?

The appeal is straightforward: you already own the hardware. Instead of spending money on an external display, you repurpose an existing laptop screen to extend your desktop, move windows across screens, or keep reference material visible while you work on your primary machine.

This works in more situations than most people realize — but the method you use, and how well it performs, depends heavily on your operating systems, hardware, and network environment.

The Main Methods Available

🖥️ Built-In OS Features (Windows and Mac)

Windows 11 introduced a native feature called Miracast-based wireless display, but the more reliable built-in option for laptop-to-laptop use is found through the "Projecting to this PC" settings. One Windows laptop acts as the host display; the other connects to it wirelessly over your local network using the Connect app. This requires both machines to support Miracast and be on the same Wi-Fi network.

Apple's Sidecar is a well-known example of a similar concept, but it's designed specifically for pairing a Mac with an iPad, not Mac-to-Mac. If both laptops are Macs, there's no native equivalent built into macOS for screen sharing as an extended display — which pushes most users toward third-party software.

Third-Party Software Solutions

Several applications fill the gap where native OS features fall short, and they're often the most flexible option regardless of which operating systems you're mixing.

Popular categories include:

• LAN-based display apps — These route the video signal over your local network. They generally offer lower latency than internet-dependent tools, but performance still varies based on your router, cable vs. Wi-Fi, and resolution settings.
• USB/cable-based solutions — Some software allows you to connect the two laptops with a USB or USB-C cable and treats the secondary laptop as a wired display. This typically produces more consistent results than wireless methods.
• Cross-platform tools — If one laptop runs Windows and the other runs macOS or Linux, cross-platform apps become the practical path. These applications install a client on each machine and handle the display bridging regardless of OS.

Well-known software in this space includes Deskreen, Space Desk, and Luna Display (hardware dongle), among others. Each has different approaches to latency, resolution support, and network requirements.

HDMI or Capture Card Methods

If you want a hardware-only approach, one workaround involves a video capture card. You'd connect the primary laptop's HDMI output to a capture card, then plug that into the secondary laptop's USB port, and use software on the secondary machine to display the captured video feed. This is more involved to set up and introduces its own latency, but it works entirely offline and doesn't depend on software drivers syncing correctly between machines.

This method is more common among content creators or streamers who already own capture hardware.

Key Variables That Affect Your Results

Not every setup performs the same way. These are the factors that matter most:

What "Good Enough" Actually Looks Like

For document work, email, dashboards, or reference browsing, most software-based wireless methods are entirely usable. Latency in the 30–100ms range is noticeable but tolerable when you're not interacting heavily with the secondary screen.

For video playback or anything requiring smooth motion, wireless laptop-to-laptop setups often struggle. You'll see stuttering or audio sync issues unless you're using a wired connection or a particularly fast local network.

For gaming or GPU-accelerated work, this approach generally isn't a replacement for a proper external monitor. The added encoding/decoding overhead and latency introduced by any of these methods makes it unsuitable for performance-sensitive tasks.

💡 The Setup Process in General Terms

Regardless of which method you use, the process typically follows this pattern:

1. Choose your software or method based on your OS combination
2. Install the required app on both laptops (for software-based methods)
3. Connect both devices — either to the same network or directly via cable
4. Configure display settings on your primary laptop (extend vs. mirror)
5. Adjust resolution and position in your OS display settings

Native OS methods usually require less configuration. Third-party apps often provide more granular control over resolution, frame rate, and display arrangement.

What Your Setup Will Determine

The same hardware running the same software can produce noticeably different experiences depending on router quality, the age and specs of each laptop, which operating systems are involved, and what you're actually doing on that secondary screen.

Someone running two modern Windows laptops on a gigabit wired LAN using SpaceDesk for reference browsing will have a fundamentally different experience than someone trying to mirror a Mac to an older Windows machine over shared Wi-Fi. Both are "using a laptop as a second monitor" — but the practical reality of each setup is its own thing. 🔍