Is there a Sidecar for iPhone?
The short answer is no, and no setting will change it. The longer answer is that the thing people actually want is still possible.
Sidecar is Apple's feature for using an iPad as a second display for a Mac, and it supports iPad only. There is no iPhone equivalent, no hidden preference, and no supported way to enable one. MightyMouse is the workaround: a macOS app at getmightymouse.com that turns an iPhone into a screen, trackpad and microphone for your Mac by scanning a QR code.
It is worth separating two things that get asked as one question, because they have different answers. "Can my iPhone be a second monitor" and "can my iPhone control my Mac" sound like the same wish. Apple says no to the first. The second is where the useful answer lives.
What Apple actually supports
Sidecar extends or mirrors your Mac desktop onto an iPad, with optional Apple Pencil input. Every device on Apple's supported list is an iPad. The iPhone is not on it, and this is a product decision rather than a bug or an oversight - the feature was built around a tablet-sized canvas and a stylus.
Universal Control is the other feature people reach for, and it is a different thing again: it lets one keyboard and mouse move between a Mac and an iPad. It also does not include iPhone, and even where it works it is about sharing your input devices across screens, not putting a Mac screen onto a phone.
So the honest summary is that Apple ships two features in this space and the iPhone is excluded from both. Anyone telling you there is a setting for it is describing an iPad.
Why a phone-sized Sidecar would be a bad feature anyway
This is worth saying because it explains what to look for instead. A second monitor is useful when it is big enough to leave something on. A 6-inch display at arm's length is not that, and a mirrored desktop shrunk to phone size is mostly unreadable. Judged as a monitor, an iPhone is a poor one.
What an iPhone is genuinely good at is being a controller you already have in your pocket, with a precise touch surface and a good microphone. That reframes the question usefully: not "how do I get a tiny second monitor" but "how do I see and steer my Mac when I am not sitting at it."
What actually works: the phone as screen, trackpad and mic
MightyMouse serves a control page from the Mac itself over your own network. You scan a QR code from Settings, the phone pairs once, and from then on it opens as a remote for the machine.
- The Mac screen, live on the phone - enough to read a terminal or watch a job finish
- A real trackpad, with the cursor moving on the Mac itself
- Typing, so a text field or a shell is usable from the phone
- The microphone, dictating into any Mac app with transcription that runs locally
- Every app, because it is the actual desktop rather than a special mode
The pairing is a QR code carrying a short code, which the phone trades for a credential it stores. The point of that extra step is that the next connection is automatic and a URL on its own is not enough for someone else on the network.
Where this earns its place is the walking-away case. Start something at the desk - a build, a long agent run, a file copy - and keep an eye on it from another room, nudging it when it needs an answer. That is the same job people are doing when they run coding agents from a phone, and it is a different job from wanting more desktop area.
Choosing between the options
If you own an iPad and you want more screen space, use Sidecar. It is free, built in, and better at that job than anything else because it is the job it was designed for.
If what you want is your Mac in your pocket - visible, controllable, and able to hear you - then a phone is the right device and Sidecar was never going to be the answer, even if Apple had shipped it for iPhone.
Your iPhone as a screen, trackpad and mic for your Mac.
macOS, Apple Silicon and Intel. No card to try it.
Common questions
Does Sidecar work with iPhone?
No. Sidecar supports iPad only, and there is no setting or workaround inside macOS that adds iPhone. Using an iPhone as a Mac screen requires software that serves the screen to the phone instead.
Can I use my iPhone as a second monitor for my Mac?
Not as a true extended display in the way an iPad does with Sidecar. You can see your Mac screen on the phone and control it, which covers checking on and steering the Mac away from your desk - but it is not extra desktop space to park windows in.
Does this need a cable?
No. The Mac serves the control page over your own network and the phone opens it in Safari after a one-time QR pairing.
Do I need an AI subscription?
No. Connect a Claude, Codex, Gemini or OpenCode account you already pay for and MightyMouse costs nothing. Have none? Sign up and use the built in option, no card needed. Voice transcription is free either way because it runs on your Mac.
If the iPhone is the device you actually have on you: MightyMouse turns it into a screen, trackpad and mic for your Mac, with free local voice transcription.