Can you use an iPhone as a second monitor for your Mac?
You have a spare screen in your pocket and a Mac that could use one more. Apple will not connect them for you, so the real question is which app does it well enough to be worth the trouble.
Short answer: Yes, an iPhone can be a second monitor for a Mac, but not through Apple's Sidecar, which supports iPad only, so you need an app. Duet Display and Splashtop Wired XDisplay are App Store options, and MightyMouse can add a second screen to your Mac that you watch and tap from your iPhone.
Type this question into Google and the first answers are about iPads. That is no accident. Apple built a second-screen feature, and it only works with the iPad. Everything else on this page exists because of that gap.
Why Sidecar will not do it
Apple's Sidecar support page describes using an iPad with a Mac, either extending your desktop onto it or mirroring it. iPhone is not on the page. There is no setting that adds it. If you want to know exactly where that line sits and what Apple does offer, the Sidecar for iPhone page covers it, so this article skips ahead to what you can actually do.
Mirror or extend: the difference that matters
Every app in this space does one or both of two things, and they feel very different.
- Mirror. The phone shows a copy of the screen your Mac already has. Move a window on the Mac and it moves on the phone. Nothing new is added to the Mac. It is a viewer.
- Extend. The Mac believes it has one more monitor. It appears in System Settings under Displays, you can drag windows onto it, and your main screen keeps showing something else. It is a place to put things.
Mirroring is easy and works for watching. Extending is what people mean by "second monitor". It is also harder to build, because, as far as we can tell, macOS has no documented public way for an app to add a screen that is not plugged in.
What a 6-inch screen is actually good for
Be honest with yourself before you set anything up. A phone is not a monitor. You will not lay out a spreadsheet on it. It earns its place when the thing you put there is small and you want it always visible:
- A status screen. A build running, a dashboard, a log you glance at.
- Chat. Slack or Messages parked on the phone so it stops stealing room from your main screen.
- A terminal. One small window where a command is running.
- Watching an agent work. If you run a coding assistant, a phone screen on the desk lets you see what it is doing without giving up a window.
- Music or notes. A player, a timer or a scratch note that lives apart from your real work.
Where it does badly: anything with a lot of text, anything you need precise clicks on, and anything where you need sharp color. Small targets and a thumb-sized screen add up. Also expect the phone battery to drain faster than usual, so keep a charger nearby.
The App Store options
These are the two names that come up most. Facts below come from their own pages, as of October 2026. Prices and requirements change, so check the listing before you pay.
Duet Display. Its own site says you can "use your Mac, PC, iPad, iPhone, or Android device as a second display," and also lists a newer feature for putting your iPhone or iPad screen on your Mac and controlling it with your keyboard and mouse. The Mac app lists macOS 12.3 or later for Apple Silicon. The page does not show a price.
Splashtop Wired XDisplay. Splashtop's page lists "all iPhones and Android phones" as compatible. One thing to read closely before you buy: the same page gives the computer requirement as "macOS 10.13.6 and below or Windows 7+". That is an old macOS ceiling, so confirm it works on your current Mac before paying for it. The name says wired, and the page does not describe a wireless option.
There is also a free open-source option. OpenDisplay, as described on AlternativeTo, covers iPhone and iPad as a second display for a Mac over USB or Wi-Fi, under the GPL-3.0 license. That is a third-party summary rather than the developer's own page, so read the project's own notes before you rely on it.
If your real need is a drawing tablet rather than a second desk screen, that is a different job, covered in the Astropad Workbench comparison.
Where MightyMouse fits, and what it really does
MightyMouse turns your iPhone into a live screen, trackpad, keyboard and mic for your Mac. It runs on the Mac and your iPhone opens a page in Safari after you scan a QR code, so nothing is installed from the App Store. The screen part has two settings, and here is exactly what each one does.
Same screen. This is the default. Your phone shows your Mac's main screen live. You can tap and drag on it to move the cursor, so it is a mirror you can also drive. This is what mirroring your Mac to your iPhone is about, and what controlling your Mac from your iPhone builds on.
Second screen. This is the extend option. Turn it on and the Mac adds a new display called MightyMouse. Your real monitor keeps showing your own work, and the phone shows the new display. Drag a window to it and it appears on the phone.
How to turn on the second screen
- Open MightyMouse on your Mac and pair your iPhone by scanning the QR code.
- On the phone page, open Settings and find the Screen section.
- Turn on "Show my Mac screen".
- Under "Show", choose "Second screen" instead of "Same screen".
- On your Mac, open System Settings, then Displays. A display named MightyMouse is there. Drag a window onto it.
- To remove it, start the screen again with "Same screen" chosen, or quit MightyMouse. Turning the screen off alone leaves the extra display in place.
The settings screen describes it in its own words: "Give your Mac a second screen. Your monitor keeps showing your own work, and the screen stays after you disconnect." That second sentence is real behavior. If your phone drops off, the extra display stays on the Mac with your windows on it, until you remove it or quit the app.
What this costs you and where it falls short
This is the part most articles skip. Be clear about it before you decide.
- It uses an undocumented macOS feature. Apple has no public way to create a display out of nothing. MightyMouse uses a private macOS interface, CGVirtualDisplay, that Apple does not document. Apple can change or remove it in any macOS update. If that happens, the Second screen option fails and you see "This Mac can't add a second screen". Same screen keeps working.
- The screen needs Screen Recording permission. The Mac has to let MightyMouse capture the screen, and only you can grant that, on the Mac itself.
- Only one extra display, and only the phone starts it. You cannot start the screen from the Mac side, and you cannot add two phone displays.
- The shape is a Mac screen, not a phone screen. The new display is sized to match your Mac's main display, so on a phone held upright it can show as a wide picture with empty bars above and below.
- It is not a wired, zero-lag cable. The picture travels over your network, so there is a small delay. On your own Wi-Fi it is fine for status and chat. It is the wrong tool for video editing or fast games.
- It needs an awake Mac. A sleeping Mac cannot offer its screen, and a locked screen is a wall MightyMouse cannot get past.
- macOS only. The second screen is a Mac feature. A Windows version of MightyMouse is in beta, and it does not include this.
- It is not in the App Store. Because of that private interface, this feature ships in the downloaded Mac app only.
Apart from that, using the phone as a screen, trackpad and keyboard on your own Wi-Fi is free and unlimited. Away from home it works over cellular, with a free monthly allowance for that part.
Which one should you pick?
If you want a wired, low-delay panel for steady work, a paid app built for that, such as Duet Display or Splashtop Wired XDisplay, is the straightforward pick. Check the macOS version each one supports for your Mac first.
If you want a glanceable extra screen on the desk that you can also tap, move windows on, and use to watch what is running while you are away from the desk, with nothing to install on the phone, try the Second screen setting in MightyMouse. If it does not suit you, switch back to Same screen and you still have a live view of the Mac in your hand.
And if you actually want an iPad as a second monitor with Apple Pencil, that is what Sidecar is for, and it is free.
Give your Mac a second screen on your iPhone.
No app to install. No card to try it.
Common questions
Can I use my iPhone as a second monitor for my Mac?
Yes, with an app. Apple's Sidecar only supports iPad, so an iPhone needs Duet Display, Splashtop Wired XDisplay or MightyMouse, which can add a second screen to your Mac and show it on your phone.
Does Sidecar work with iPhone?
No. Apple's Sidecar support page describes using an iPad with a Mac, and there is no setting that adds iPhone.
What is the difference between mirroring and extending my Mac to an iPhone?
Mirroring shows a copy of your Mac's screen on the phone. Extending adds a separate display that your Mac treats as another monitor, so you can drag windows onto it while your main screen shows something else.
Can I use my iPhone as an external monitor for a MacBook for free?
Sometimes. MightyMouse's screen, trackpad and keyboard are free on your own Wi-Fi, and an open-source app called OpenDisplay is listed as free. Many App Store display apps charge, so check each listing.
Is an iPhone screen big enough to be a second monitor?
Only for small things. It works for a status screen, chat, a terminal, a music player or notes. It is a poor fit for spreadsheets, editing or anything that needs precise clicks.
Does the iPhone second screen work over Wi-Fi or does it need a cable?
It depends on the app. Splashtop Wired XDisplay is wired. MightyMouse sends the screen over your network, so no cable is needed, with a small delay compared with a wired connection.
Want a live view of your Mac in your hand? MightyMouse turns your iPhone into a screen, trackpad and mic for your Mac, and can add a second screen too.