How to Use a Laptop as a PC Monitor (Extended Display or Second Screen)

Using a laptop as a monitor for another computer sounds straightforward, but the reality depends heavily on your hardware, operating system, and what you're actually trying to accomplish. Here's what you need to know before you start — and why the answer isn't the same for everyone.

What "Using a Laptop as a Monitor" Actually Means

When people search for this, they usually mean one of two things:

• Displaying output from a desktop PC (or another laptop) on a laptop screen
• Extending their workspace using the laptop as a secondary display

These are related goals, but they work very differently under the hood. A laptop screen is driven by its own internal GPU and display controller — it's not a passive panel waiting to accept video input the way a standalone monitor is. That distinction shapes everything about how this is (or isn't) possible.

The Hardware Reality: HDMI In vs. HDMI Out

Most laptops have an HDMI output port, not an input. That port is designed to send video to an external monitor — not receive video from another device. Plugging an HDMI cable between two laptops and expecting one to display the other's screen won't work.

A small number of laptops — historically some gaming and multimedia models — have included an HDMI input port, which does allow true hardware-level video capture from another machine. If your laptop has this, it functions more like a traditional monitor for the source device.

To tell them apart:

• Check your laptop's spec sheet or manual for "HDMI In" explicitly
• Look for dual HDMI ports (one in, one out) — a rare but real configuration
• Assume output-only if specs are unclear — that's the more common case by a wide margin

Software-Based Methods: The More Common Approach 🖥️

Since most laptops lack HDMI input, software solutions fill the gap. These work by transmitting the video signal over a local network (LAN or Wi-Fi) rather than a direct cable connection.

Windows: Wireless Display (Miracast)

Windows 10 and 11 include a built-in feature that allows one Windows machine to project its screen to another over Wi-Fi using the Miracast protocol.

On the laptop acting as the display:

• Open Settings → System → Projecting to this PC
• Configure who can project and whether a PIN is required
• The laptop must support Miracast reception (most modern Windows laptops do)

On the source PC:

• Press Windows + K to open the Cast menu
• Select the target laptop from the available devices

This method supports both duplicate and extended display modes, making it genuinely useful for productivity setups. Performance depends on your network speed and signal quality — Wi-Fi 5 or Wi-Fi 6 connections generally handle this better than older standards.

Third-Party Software Options

Several well-known applications enable laptop-as-monitor functionality across platforms:

These apps vary in latency, resolution support, and whether they require subscriptions or one-time purchases. Software-based solutions generally introduce some display lag, which matters more for video editing or gaming than for document work.

macOS: Sidecar and AirPlay

Apple's Sidecar feature lets a compatible Mac use an iPad as a second display — but it doesn't extend natively to using another Mac laptop as a monitor. AirPlay to Mac (introduced in macOS Monterey) does allow one Mac to receive screen content from another Apple device, which partially bridges this gap for Apple-ecosystem users.

Compatibility requirements apply for both features, and not all Mac models support receiving AirPlay input even on supported OS versions.

What Affects Performance and Usability

Even when the connection works, the experience can vary considerably:

• Network quality — A wired LAN connection between two machines (via a router or direct cable with IP configuration) is significantly more stable than Wi-Fi for screen-sharing workloads
• Laptop specs — Older laptops may struggle to decode and render an incoming stream smoothly while running their own OS
• Resolution and refresh rate — Software methods rarely match the native refresh rate and sharpness of a physical second monitor; most cap out at 1080p/60Hz in practice
• Use case — Static tasks like coding, writing, or spreadsheets tolerate latency well; video playback, gaming, or design work will expose limitations faster

The KVM and Capture Card Route

For users who need reliable, low-latency performance — and are willing to invest in hardware — a video capture card is a different approach. A capture card sits between the source device and the laptop, converting HDMI output into a USB signal the laptop reads as a camera or input device.

This is common in game capture and streaming setups but works for any HDMI source. Latency is still present but is often lower than pure software methods, and some professional capture cards offer near-real-time previews. The tradeoff is cost, the need for capture software, and the fact that the laptop is processing video rather than displaying it directly.

KVM switches solve a related but different problem — they let you control multiple computers from one keyboard, mouse, and monitor — and are sometimes confused with second-screen solutions.

The Variables That Determine Your Best Path 🔧

Whether any of these methods works well for your situation depends on factors that aren't universal:

• What OS each machine runs (Windows, macOS, Linux, or mixed)
• Whether your laptop has Miracast support or a rare HDMI input
• The quality and type of your network connection
• Whether you need the display for static tasks or high-performance work
• Your tolerance for software setup and occasional connection troubleshooting

A setup that works seamlessly for a developer using a wired LAN may perform poorly for someone on a congested Wi-Fi network trying to play video. The right method — and whether the result meets your standards — depends entirely on the combination of hardware, software, and network conditions you're actually working with.