Why Use Your Phone as a Second Monitor
A second monitor is one of the simplest ways to improve how you work. It lets you keep your main task in front of you while messages, music, notes, or reference material sit off to the side, visible at a glance. A real second monitor costs money and takes up desk space, but your phone is already there, with a sharp, bright screen, doing nothing while you work.
Turning your phone into a second monitor means your computer treats it as an extra display. You can drag a window onto it, just as you would with a normal monitor, and it stays there while you work on your main screen. It will never replace a full-size monitor for design or video work, but for everyday jobs it is surprisingly useful: a chat window, a music player, a to-do list, or a document you need to check while you type.
It is also ideal away from your desk. In a library, a cafe, or on a trip with a laptop, you probably have no spare monitor, but you do have your phone. This guide explains the options, walks you through one wireless setup and one wired USB setup, shows you how to arrange the display in Windows, and covers lag, battery drain, and touch input.
Wired vs Wireless: Which Way Should You Connect?
Wireless is the most convenient option. You need no cable, your phone stays free to pick up, and setup is usually just putting both devices on the same Wi-Fi network and tapping connect. The downside is lag: the picture travels over Wi-Fi, so there is a small delay before changes on your computer appear on your phone. For static content such as chat, email, a document, or a music player, that delay does not matter. For video or fast scrolling, you will notice it.
A wired USB connection is faster and more stable. The picture travels over the cable, so the delay is much smaller, the image looks sharper, and the connection does not drop when Wi-Fi is weak. The phone also charges while connected. The downside is that your phone is tied to your computer, and you need a cable that supports data, not just charging. Some cheap cables only carry power, so if a USB setup fails, check the cable first. Use Wi-Fi for convenience and static content, and USB for the smoothest picture, unreliable Wi-Fi, or long sessions.
Your Options at a Glance
Spacedesk
Spacedesk is a free app that turns Android phones and tablets, and iPhones and iPads, into extra displays for a Windows computer. It works over Wi-Fi and over USB, so you can try wireless and switch to a cable later without changing apps. It needs no account, and its basic features are free. It is the app this guide uses for both step-by-step setups below.
Duet Display
Duet Display is a long-running app that does the same job on Android and iPhone, for Windows and Mac computers. It works over Wi-Fi and a wired connection, and is known for a smoother picture and better touch support than most free options. It offers a free tier with basic features, with more advanced features as a paid upgrade. If you plan to use your phone as a second monitor every day, it is worth trying after you have tested the free option.
Built-in Options Where They Exist
Windows itself has no built-in feature that turns a phone into a second monitor, so on a Windows computer you will need one of the apps above. Apple offers Sidecar, which turns an iPad into a second display for a Mac, but it works with iPads, not iPhones, and only with a Mac, not a Windows PC. Some Android makers include screen-sharing features, but these usually mirror your phone onto your computer, the opposite of what you want. In practice, most people use a third-party app.
Method 1: Set Up a Wireless Second Monitor with Spacedesk
This is the easiest way to start. You need a Windows computer, an Android phone or an iPhone, and a Wi-Fi network both devices share. It takes about five minutes.
Step 1: Install the Spacedesk driver on your Windows computer. On your computer, go to the Spacedesk website, download the driver for Windows, and run the installer. Accept the usual prompts, let it finish, and restart if asked. The driver lets Windows see your phone as a real display, so the phone app cannot work without it.
Step 2: Install the Spacedesk app on your phone. Open the Play Store on Android or the App Store on iPhone, search for Spacedesk, and install the free app. Open it once, and allow any permissions it asks for, such as local network access, so it can find your computer.
Step 3: Make sure both devices are on the same Wi-Fi network. Check the network name on your computer and your phone and confirm they match. If your phone is using mobile data, turn Wi-Fi on and join the same network. If your computer uses Ethernet while your phone uses Wi-Fi, that is usually fine on the same home network, but if the phone cannot find the computer, try putting the computer on Wi-Fi too.
Step 4: Connect from the phone app. Open the Spacedesk app on your phone. After a few seconds it should list your computer by name. Tap it to connect. The phone screen will go dark briefly, then show part of your Windows desktop, usually a blank extended desktop with your wallpaper. That is correct: Windows has added your phone as a second display, waiting for you to drag a window onto it.
Step 5: Drag a window onto your phone. On your computer, click the title bar of any window, such as your messaging app or music player, and drag it to the edge of your main screen in the direction of the phone. Keep dragging, and the window will appear on your phone. If you are unsure which direction to drag, check the arrangement in Display settings, covered later in this guide.
Method 2: Set Up a USB Second Monitor
Step 1: Install the driver and the app first. If you already followed the wireless method, skip this step: the driver and app are the same for both methods. If not, follow steps 1 and 2 of the wireless method above first.
Step 2: Connect the cable and choose the right USB mode on Android. Plug the cable into your phone and computer. On Android, a notification should say the phone is charging over USB. Tap it and change the mode to file transfer or tethering, depending on your phone. You want a mode that lets the phone exchange data with the computer, not charging only. On iPhone, tap Trust if asked whether to trust the computer, and enter your passcode.
Step 3: Turn on USB tethering if the app asks for it. Some Android phones need USB tethering on before a USB display connection will work, because the app uses that link to talk to the computer. Go to Settings, then Connections or Network, then Mobile Hotspot and Tethering, and turn on USB tethering. If your phone does not need it, the option may be greyed out; just continue. Your mobile data can stay off: the link only connects phone to computer, not sharing internet.
Step 4: Connect from the phone app. Open the Spacedesk app on your phone. Your computer should appear in the list, this time as a USB connection. Tap it to connect. Your phone will show your extended Windows desktop, as over Wi-Fi, but smoother and sharper.
Step 5: Test dragging a window and check the charging icon. Drag a window onto the phone screen, and check that the phone is charging. If it is, you can leave it plugged in for a full session without worrying about the battery. If the connection drops when you move the cable, try a different cable or USB port: a loose or worn cable is the most common cause of an unstable USB connection.
How to Set Up Duet Display
If you would rather use Duet Display, setup follows the same pattern: an app on your phone, a companion program on your computer, then a connection over Wi-Fi or cable. Install Duet Display from the Play Store or App Store, then install the Duet companion program on your Windows computer from the Duet website and restart if asked. Open the app on both devices, sign in if asked to create an account, and connect over the same Wi-Fi network or a USB cable.
How to Arrange the Display in Windows Settings
Once connected, Windows treats your phone as a second monitor, and you can arrange it like a physical one. If the arrangement in settings does not match where your phone actually sits on your desk, dragging windows onto it will feel wrong.
Step 1: Open Display settings. Right-click an empty area of your Windows desktop and choose Display settings, or open Settings, then System, then Display. You should see two numbered boxes, labelled 1 and 2. One is your main monitor, the other is your phone. If you see only one box, your phone is not connected yet, so go back to the app and tap connect again.
Step 2: Drag the boxes to match your desk. Drag the phone’s box to the side where the phone actually sits: right if it is on the right of your monitor, left if it is on the left, below if it is below. Windows uses this layout to decide which edge a window crosses when you drag it, so matching the real layout makes dragging feel natural.
Step 3: Check that Extend is selected, not Duplicate. Scroll to Multiple displays. It should say Extend these displays, meaning your phone shows extra space beside your main screen. If it says Duplicate these displays, your phone will only copy your main screen. Change it to Extend these displays and click Apply.
Step 4: Adjust resolution and orientation. With your phone selected, you can change its resolution and orientation. A lower resolution often looks better on a small screen and runs more smoothly, while a higher one shows more detail. Use Landscape if the phone lies sideways, or Portrait if it stands upright, which suits a long chat thread or document. Click Apply and keep the changes if they look right. Your main monitor should stay as your main display, so your taskbar and new windows open there.
Practical Uses for a Phone Second Monitor
- Chat and messages. Keep your messaging app, email inbox, or team chat on your phone while you work. You can see new messages without switching windows, and reply without losing your place.
- Music and podcasts. Put your music or podcast player on the phone screen, so you can see what is playing, skip a track, or change a playlist without covering your work.
- Monitoring and dashboards. A live feed, download progress bar, system monitor, or social media dashboard fits well here. It updates in the background, and a quick glance tells you whether anything needs attention.
- Reading and reference material. Keep a document, notes, a recipe, a timetable, or a web page open on the phone while you type on the main screen, instead of switching back and forth between windows.
Dealing with Lag, Battery Drain, and Touch Input
Lag
Lag is the delay between something changing on your computer and it appearing on your phone. Over Wi-Fi, a small delay is normal, and it gets worse with a weak signal, many devices on the same network, or a phone far from the router. Move closer to the router, lower the resolution or frame rate in the display app, and close other apps on your phone that use the network. If lag is still a problem, switch to USB, which removes Wi-Fi entirely. Lag also matters less for static content: a chat window or document does not need constant updates, so a small delay is invisible in normal use.
Battery Drain
Acting as a display keeps your phone screen on, the Wi-Fi or USB link active, and the processor working, so the battery drains faster than normal. Over a long session, a phone that is not charging can lose a large part of its charge in an hour or two. The easiest fix is a USB connection, which charges the phone while you work. Over Wi-Fi, plug the phone into a charger at the same time, or keep sessions short. Lowering screen brightness also helps, and disconnecting in the app when you step away saves power.
Touch Input
Touch support depends on the app and on Windows. In most free setups, touching the phone screen does nothing, or only moves the mouse pointer without clicking reliably. Your phone is acting as a display, not as a touchscreen for your computer, so your computer’s keyboard and mouse remain the way you control what is on the phone screen. Some apps, including Duet Display, offer better touch support, letting you tap and scroll on the phone screen, but even then it is not as smooth as a real touchscreen monitor. Treat the phone screen as view-only: look at it, and control it with your mouse and keyboard. To interact with an app there, drag it back to your main monitor, use it, and drag it back.
Common Problems and How to Fix Them
Your phone cannot find your computer. This is almost always a network problem. Check both devices are on the same Wi-Fi network, and that the phone is not on a guest network or hotspot while the computer is on the home network. Restart the app on your phone, then the companion program or driver on your computer. A firewall can also block the connection, so allow the firewall prompt if the app shows one when you install the driver.
The picture is blurry or the movement is choppy. Lower the resolution and frame rate in the app settings. A smaller, smoother picture is more useful than a large, stuttering one. Move closer to your Wi-Fi router, or switch to a USB cable. Also check your computer is not running a heavy task, such as a video render or large download, which can slow the display app.
The connection keeps dropping. On Wi-Fi, a weak signal or interference is the usual cause. Move closer to the router, or use the 5 GHz band if your router offers one, because it is often less crowded. On USB, the cause is usually the cable: try a different cable or port. A cable that only charges and does not carry data will never work for a USB display, so use one you know works for file transfer.
Frequently Asked Questions
Can I use my phone as a second monitor for free? Yes. Spacedesk is free, and it covers the basic job well over Wi-Fi and USB. Paid apps exist, and they usually offer a smoother picture or better touch support, but you do not need to pay anything to try the idea and see whether it suits how you work.
Does this work with an iPhone as well as an Android phone? Yes. The apps in this guide have versions for both Android and iPhone. Setup is the same in principle: install the driver on the computer, install the app on the phone, and connect over Wi-Fi or USB. The menus and permission prompts differ slightly, but the idea is identical.
Will it work without Wi-Fi? Yes, if you use a USB cable. A wired connection needs no Wi-Fi at all, which makes it the best choice when travelling, when Wi-Fi is unreliable, or on a network that blocks devices from talking to each other. A wireless connection does need both devices on the same Wi-Fi network.
Final Thoughts
Using your phone as a second monitor will not replace a real monitor, but that is not the point. It takes a device you already own, a free app, and a few minutes of setup, and gives you extra screen space exactly when you need it, at your desk, in a library, or on the road. Start with the wireless method, because it is the quickest way to see whether you like the idea. If you do, try USB for longer sessions, arrange the display properly in Windows settings, and put something genuinely useful on the small screen, such as chat, music, or notes.
Facebook comments