Use a Raspberry Pi 4 as a Second Monitor or KVM in 2026

Yes — in 2026 a Raspberry Pi 4 Model B makes a workable second monitor or USB-attached KVM when paired with the right software stack and a real HDMI capture path. As a second display, the Pi runs Spacedesk or Synergy clients reliably; as a KVM, a Pi 4 with the PiKVM-CM4 stack switches between machines with sub-100ms input latency and 1080p30 video. Either build comes in under $150 if you already own the Pi.

Why repurpose a Pi 4 instead of buying a monitor or hardware KVM?

The Pi 4 has been over-deployed in homelabs since 2020. Many readers have a spare 4GB or 8GB Pi sitting in a drawer that they were going to "use for something." Two of the best somethings in 2026 are turning it into a second-display node for your laptop or workstation, or building a network KVM that can swap a single monitor + keyboard + mouse between multiple machines remotely.

The economics work because both use cases have premium-priced commercial alternatives:

• A small portable USB monitor: $150-300.
• A hardware IP-KVM (Lantronix, Raritan): $500-2,000.
• A consumer KVM switch with a fixed monitor: $80-200 for 2-port versions.

A Pi 4 + cables + (for the KVM build) one optional HDMI capture board comes in well under the lowest of those, and the build gives you flexibility the commercial gear doesn't — for example, you can route the second display over Wi-Fi to a laptop sitting on a coffee table.

This piece is a synthesis of community build guides (the PiKVM project, the Spacedesk forums) and the Raspberry Pi product documentation for the Pi 4 platform.

Key takeaways

• Second-monitor mode: software-only build using Spacedesk or Synergy — Pi + monitor, no extra hardware.
• KVM mode: needs an HDMI capture HAT or PiKVM-CM4 board; switches between 2+ machines with sub-100ms input lag.
• Wired Ethernet is required for both — wireless latency makes either use case painful.
• A spare 1080p monitor is the natural display pair for both builds.
• Storage barely matters — both builds run from a 32GB microSD or a small SATA SSD.
• The Pi 5 works too but isn't necessary — Pi 4 8GB is plenty for either workload.

Build option 1 — Second monitor over network (Spacedesk)

Spacedesk is a Windows-side server + multi-platform client that extends your desktop to any device with a display. The Pi 4 runs the Spacedesk Linux client, displays your extended desktop, and shows up in Windows display settings as a real second monitor (drag windows to it, set wallpaper, the works).

Bill of materials:

• Raspberry Pi 4 Model B 8GB — $75 (4GB version at $55 also works).
• Spare 1080p HDMI monitor — free if you have one, $80-130 if buying.
• Standard HDMI cable, microSD card, power supply — $20 total.
• Ethernet cable to your router — $8.

Total: $108 + monitor. If you already have the monitor and the Pi, you're looking at $28 of cables and storage.

Latency expectation: 25-50ms end-to-end input-to-display over wired Ethernet. Fine for documents, browser tabs, monitoring dashboards, Discord. Not fine for fast-paced gaming.

Setup steps: install Raspberry Pi OS 64-bit, download the Linux Spacedesk client, install on Windows side, connect over LAN.

Build option 2 — Second monitor for Mac/Linux (Synergy + sunshine/moonlight)

Spacedesk is Windows-centric. For Mac or Linux primary machines, the combination is different but the principle is the same:

• Synergy for the keyboard/mouse extension across machines.
• Sunshine (server) + Moonlight (client) for screen sharing.

The Pi 4 runs Moonlight as a thin display client. Sunshine on your primary Mac/Linux box streams the extended display. Latency is comparable to Spacedesk on Windows.

For both setups, a 27" 4K monitor like the SANSUI at $200 makes a beautiful secondary panel — though for second-monitor use, 1080p is plenty and saves cost.

Build option 3 — Pi KVM (network IP-KVM)

The PiKVM project turns a Pi into a full network KVM-over-IP: it captures HDMI from a target machine, serves it over a web browser, and emulates keyboard + mouse via USB OTG so the target machine sees the Pi as a real keyboard. You can remotely operate a machine that's powered off, BIOS-level, no OS — useful for headless servers, remote pair-programming setups, or running a homelab where you don't want a monitor for each machine.

Bill of materials:

• Raspberry Pi 4 Model B 8GB — $75.
• PiKVM v3 HAT (HDMI capture + USB OTG breakout) — $130 (most expensive part).
• Spare HDMI monitor — only needed for setup, optional after.
• microSD card, Ethernet cable — $15.
• USB-A to USB-A cable for OTG to target — $5.

Total: $225 for a single-port IP-KVM. Compare to a commercial Lantronix Spider or similar: $500-1,500.

Capabilities: 1080p30 video stream, sub-100ms keyboard/mouse latency, web-based UI accessible from any browser, supports virtual mass storage (mount an ISO from the Pi as if it were a USB stick on the target).

Storage and CPU requirements — what the Pi actually does

For the second-monitor build, the Pi is doing network video decoding. CPU load is low (5-15% on a Pi 4). Storage needs are tiny (the OS plus the client).

For the KVM build, the Pi is doing HDMI capture, video encoding (typically H.264 at 1080p30), keyboard/mouse emulation, and serving a web UI. CPU load is moderate (25-50%). Storage is again small but the OS should be on a real SATA SSD (Samsung 870 EVO 250GB over a FIDECO USB 3 adapter) for write reliability — KVM logs accumulate.

The Pi 4 4GB is enough for any of these. The 8GB version costs $15-20 more and gives you headroom for running additional services (Home Assistant, MQTT broker) on the same box.

Monitor pairing recommendations

For the Pi-as-second-monitor build, a 24-27" 1080p monitor at the price tier of $80-150 is the sweet spot. For the PiKVM, a 27" 4K monitor like the SANSUI 27" 4K at $200 or the KOORUI 27" QD-Mini LED gives you the resolution to actually see what's happening on the target machine; KVM video streams at 1080p30 by default but can scale down a 4K source.

For shared-monitor KVM setups (one physical monitor, multiple machines), a quality 1440p or 4K panel is worth the spend — you'll look at it for 8+ hours a day.

Common pitfalls

1. Trying to use Wi-Fi. Latency variance over Wi-Fi makes the second-monitor build feel mushy and the KVM build feel broken. Always wire it.
2. Buying a cheap HDMI capture card for PiKVM. The official PiKVM HAT is worth the price. Cheap captures introduce inconsistent latency and audio sync issues.
3. Forgetting Sunshine needs GPU. On the source machine, hardware-accelerated H.264 encoding requires a GPU. Older Macs with no discrete graphics can struggle.
4. Skipping the heatsink/case-with-fan. The Pi 4 under sustained encode load throttles without active cooling.
5. Using a long USB-A to USB-A cable for KVM OTG. Cable quality matters at USB 2.0+. Stick with cables under 1.5m.

Verdict matrix

Use the Pi as a second monitor if:

• You have a spare Pi 4 and a spare 1080p monitor.
• Your primary use is documents, browser tabs, monitoring dashboards.
• You're OK with 25-50ms latency for non-gaming use.

Build a PiKVM if:

• You have a homelab with multiple machines that occasionally need a keyboard + display.
• You want BIOS-level remote access.
• You don't want to pay $500+ for a commercial IP-KVM.

Buy a commercial alternative if:

• You need sub-20ms latency for gaming (use a real second display, not network).
• You need 4K KVM (PiKVM tops out at 1080p30 on Pi 4 hardware).
• You're managing 8+ machines and want enterprise features.

Recommended setup

For the second-monitor build, pair the Pi 4 8GB with any 1080p monitor and a wired Ethernet connection. Optional: add a SATA SSD over USB 3 for OS reliability, but a quality 32GB microSD is fine.

For the PiKVM build, the Pi 4 8GB plus the PiKVM v3 HAT plus a Samsung 870 EVO 250GB SATA SSD over USB 3 is the cleanest configuration. Pair with the KOORUI 27" QD-Mini LED 4K monitor or SANSUI 27" 4K monitor if the KVM is the primary path for managing a homelab — you'll see KVM sessions, host monitor dashboards, and ssh terminals on the same panel.

VPN setup for remote KVM access

Both Pi-second-monitor and PiKVM benefit from a VPN-layer for remote use. The cleanest 2026 pattern:

• Tailscale on the Pi and on each client device. Zero-config mesh VPN — devices find each other by hostname.
• No port-forwarding on your router. The Pi's KVM UI or display client is reachable only over Tailscale.
• Optional ACLs in Tailscale to restrict which devices can reach the Pi.

The whole setup takes 10-15 minutes. The alternative — port-forwarding KVM ports directly to the internet — is one of the single highest-risk things you can do on a home network, since the Pi is now a remote-input device for whatever target it controls. Don't.

For PiKVM specifically, the project maintains its own remote-access documentation. Their recommended path is also Tailscale or WireGuard — they don't recommend port-forwarding either.

Latency-sensitive use cases — what doesn't work

The Pi-as-second-monitor build is fine for productivity. It's not fine for:

• Fast-paced gaming — 25-50ms of network latency on top of the game's own latency is visible and frustrating.
• Audio production — clock sync between the Pi and primary machine drifts; not viable for DAW use.
• Video editing scrubbing — the codec at the network layer compresses heavily on fast pans, making preview frames artifact-heavy during scrubbing.

For each of those, buy a real second display or get a USB-C portable monitor instead. The Pi build is right for slower-changing content.

Power management

Both builds leave the Pi running 24/7. Power consumption is modest — 3-5W under typical load. Annual electricity cost is well under $10 at U.S. residential rates. The Pi 4's official power supply is rated 5.1V/3A which gives 25-30% headroom over typical draw.

For deployment in a closet without thermal management, consider a Pi 4 case with active cooling — passive cases work but throttle under sustained encode load. The $12 fan-case combos are the easy answer.

For deployment where the Pi might be unplugged accidentally (under a desk, behind a monitor), consider a small UPS or a 5V battery backup. Sudden power loss during write doesn't usually corrupt a SATA SSD but can corrupt an SD card.

Bottom line

The Pi 4 makes a workable second-monitor over network (Spacedesk for Windows, Synergy + Sunshine/Moonlight for Mac/Linux) and a genuinely good network IP-KVM with the PiKVM stack. Neither use case is going to win awards for low latency, but both are useful, both are cheap, and both put an otherwise-idle Pi to work. If you have a spare Pi 4 8GB and a spare monitor, the second-monitor build is essentially free; if you've been eyeing a commercial IP-KVM and the cost has been a blocker, the PiKVM v3 build at $225 lands at a quarter of what enterprise hardware costs.

Related guides

• Build a Plex Media Server on a Raspberry Pi 4 8GB in 2026
• Home Assistant on a Raspberry Pi 4 8GB: 2026 Smart-Home Hub Build
• Self-Host Jellyfin on a Raspberry Pi 4 8GB in 2026: Setup and Reality
• Build a Private Security Camera on a Raspberry Pi (Ring Alternative) in 2026

Citations and sources

• Raspberry Pi 4 Model B product page (8GB RAM, Gigabit Ethernet, USB 3 ports, dual micro-HDMI output)
• PiKVM project (IP-KVM software stack, HDMI capture HAT specifications, USB OTG keyboard/mouse emulation)
• Spacedesk project page (Windows-side server, Linux client for Pi, latency expectations)

This piece is editorial synthesis based on publicly available information. No independent first-party benchmarking is reported.