Micro Tech Hacks

How to Turn Your Old Phone Into a Free Second Monitor

By on Saturday, May 30, 2026

We have all felt the hardware squeeze of working on a single laptop screen. Whether you are trying to reference a research document while writing a report, keeping an eye on a messaging app, or monitoring live code output, flipping back and forth between overlapping windows drains your focus and slows you down.

Buying a dedicated portable external monitor costs anywhere from $100 to $300. But if you have an old smartphone or tablet sitting in a drawer gathering dust, you already own a vibrant, high-resolution portable display.

With the right software tools and a few minutes of configuration, you can transform that old device into a wireless or wired second monitor for your PC or Mac completely for free. Here is a step-by-step guide to making it happen.

1. What You Need Before You Start

Before downloading any apps, make sure your setup meets a few basic prerequisites:

  • The Devices: An old Android phone/tablet (running Android 5.0 or higher) or an iPhone/iPad (running iOS 12 or higher), plus your primary Windows PC or Mac.

  • The Connection: A stable local Wi-Fi network (if you want wireless pairing) or a standard USB charging cable (strongly recommended for zero-latency performance).

  • Mounting Solution: A simple phone stand, a laptop clip mount, or even a magnetic desk mount so your second screen sits comfortably at eye level next to your primary display.

2. The Best Free Tools for the Job

While several apps exist, a few reliable utilities dominate this space by offering seamless, low-latency display extension without requiring expensive software licenses:

Option A: Spacedesk (Best Free Overall for Windows & Android/iOS)

Spacedesk is widely regarded as the gold standard for multi-monitor networking. It allows your phone or tablet to function as an extension of your Windows desktop over your local network or a USB hotspot.

  • Why it shines: It is entirely free, supports multi-touch input, and works smoothly across Wi-Fi or local network connections.

Option B: Deskreen (Best Cross-Platform Open-Source Tool)

If you are running Linux, macOS, or Windows and want a browser-based solution that works with almost any device, Deskreen is fantastic.

  • Why it shines: It turns any device with a web browser into a secondary screen by converting your computer’s screen feed into a secure local web stream.

Option C: Twimight / USB-Specific Apps

If you prefer a pure wired connection via USB to completely eliminate Wi-Fi lag, dedicated USB tethering display apps offer ultra-responsive frame rates, though configuration can occasionally require developer debugging mode on older Android devices.

3. Step-by-Step Setup Guide (Using Spacedesk)

Here is how to set up a robust, lag-free secondary screen using Spacedesk in under five minutes:

Step 1: Install the Server on Your PC

  1. Go to the official Spacedesk website and download the Driver Software for your primary computer (Windows).

  2. Run the installer, accept the default settings, and ensure the driver service runs in your system tray.

Step 2: Install the App on Your Old Phone

  1. Open the Google Play Store (Android) or Apple App Store (iOS) on your old phone.

  2. Search for Spacedesk and install the free client application.

Step 3: Connect and Configure

  1. Ensure both your computer and your phone are connected to the same Wi-Fi network (or connect your phone directly to your PC via a USB cable and enable USB tethering for zero latency).

  2. Open the Spacedesk app on your phone. Your primary computer should appear automatically on the connection screen. Tap its name to connect.

  3. Once connected, your phone screen will light up as an extended desktop.

Step 4: Adjust Display Settings on Your PC

  1. Right-click your computer desktop and select Display Settings (Windows) or Displays (Mac).

  2. Drag and drop the secondary display box so it matches the physical placement of your phone on your desk (e.g., directly to the left or right of your laptop). This ensures your mouse cursor glides naturally between screens.

  3. Adjust the resolution scaling if the text appears too small on the phone screen.

Frequently Asked Questions

Q: Why is my phone screen lagging or stuttering when used as a second monitor?

A: Wireless network congestion is usually the culprit. If your Wi-Fi signal drops or suffers interference, your display stream will stutter. The easiest fix is to abandon Wi-Fi entirely and connect your phone to your PC via a USB cable, turning on USB Tethering in your phone settings for a lightning-fast, zero-lag wired connection.

Q: Can I use touch input on my phone to control my computer apps?

A: Yes! Most apps (like Spacedesk) support touch functionality. You can tap, swipe, and scroll directly on your phone screen to interact with applications, though it works best for clicking simple controls, dragging windows, or viewing static reference dashboards rather than precision design work.

Q: Will keeping my old phone plugged in and running as a monitor ruin its battery?

A: Over months of continuous use, maintaining a constant 100% charge plugged into a USB port can cause minor battery degradation. To mitigate this, try unplugging the device when you aren’t working, or if you are comfortable doing so on an older backup device, let the battery cycle down occasionally.

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