Second-screen apps for Mac, compared
Here's how the main ways to turn a spare device into a second Mac screen compare on price, hardware and what you have to install.
Click to copy. Uses Homebrew, a free and widely trusted installer for Mac apps. 7 days free, then $7.99 once.
| SpareScreen | Duet Display | Luna Display | spacedesk | |
|---|---|---|---|---|
| Price | $7.99 once | Subscription (about $49.99/year wireless) | $89.99 dongle | Free |
| Extra hardware | None | None | Dongle in your Mac | None |
| App on the device | None, just a browser | Duet app | Luna app | Viewer app |
| Works on a Mac | Yes | Yes | Yes | No, needs Windows |
| Devices | Any with a browser | With the app | iPad, Mac | With the app |
Prices checked in October 2026. Duet's from the App Store, Luna's from Astropad's store.
Try SpareScreen
- Install SpareScreen on your Mac with the line above. It opens in the menu bar.
- Allow Screen Recording when macOS asks. That lets SpareScreen show the extra screen on your tablet.
- Open the link in its browser. Click SpareScreen in the menu bar to see the link and its QR code, then open it on the tablet. Both need to be on the same Wi-Fi.
- Click Allow on the Mac. An extra screen appears, shaped exactly like your tablet. Drag windows onto it like any monitor.
Good to know
- Touch control is optional. Turn it on in the SpareScreen menu (it asks for Accessibility permission) to tap, drag, right-click and scroll on the device. Typing still happens on the Mac.
- Everyday work feels instant. Video and fast scrolling are heavier and can stutter on slow Wi-Fi; 5 GHz Wi-Fi helps.
- Streaming services stay black. Netflix, Prime Video and Disney+ block screen capture in every app like this.
- Use Wi-Fi you trust. The picture travels over your local network, never through the internet.
Questions
What's the cheapest way to add a second screen to a Mac?
Use a device you already own. SpareScreen costs $7.99 once with no hardware or subscription, and works with any tablet, phone or laptop that has a browser.
Which second-screen app needs no app on the tablet?
SpareScreen: the tablet only opens a link in its web browser.
What does SpareScreen cost?
It's free for 7 days, then $7.99 once. It's a one-time purchase with no subscription, and one key works on up to 3 Macs.
Which Macs does it work on?
Any Mac running macOS 13 Ventura or later, with Apple Silicon or Intel.
More guides
Last updated October 2026.