Duet Display alternative: use a Mac as a second display without a subscription
Duet Display is a subscription app that turns an iPad, an Android tablet, a Windows PC or another Mac into a second display. If you are looking for a Duet Display alternative because you want to use an iMac or a MacBook as a display for another Mac, this page compares Duet with DisplayBridge, the app I develop.
Every Duet fact on this page comes from Duet's own website, help center, blog and App Store listing, checked on 11 October 2026, and the table also shows where Duet is the better choice.
In short: for a 5K iMac from 2017 or later and a Mac with Thunderbolt, DisplayBridge gives you full 5K at 60 Hz, uncompressed, for $29 once instead of about $48 a year, and without an account. Duet is the better choice for iPads and Android tablets, Windows PCs, wireless use, or older Macs.
Comparison: Duet Display vs. DisplayBridge
Green: the better option in that row · Red: the worse option · No color: not comparable or not stated
| Duet Display | DisplayBridge | |
|---|---|---|
| Price | A subscription. Duet Air, the cheapest plan that includes Mac to Mac, costs $3.99 a month billed annually (about $48 a year), or $5.99 a month on the App Store. A lifetime license costs $139 | $29, paid once, for the Mac you work on. Plus a Thunderbolt cable from about $10 if you don't have one |
| Account | A Duet account, signed in with the same account on both computers | No account |
| Resolution on a 5K iMac | Up to 4K, according to Duet's own blog, at 60 frames per second. The iMac's 5K panel doesn't run at its native resolution | Full 5K at 60 Hz, uncompressed |
| Sound on the second Mac | Not mentioned anywhere on Duet's website | Yes. The Mac's sound plays through the iMac's speakers, over the same cable |
| Delay | "Zero lag", and "near-zero lag (<1ms)" over Thunderbolt, according to Duet. The 1 ms refers to the network ping of the cable connection | About 20 ms from the moment your Mac captures a frame until the iMac shows it; roughly 10 ms more than a directly connected monitor |
| Connection | Your WiFi network, or a Thunderbolt cable (Thunderbolt needs macOS 12.3 or later on both Macs) | A Thunderbolt cable or a 40 Gbit/s USB-C cable (USB4) only |
| Macs that can be the display | Macs on macOS 10.14.4 Mojave or later | Macs with Thunderbolt 3 or 4 on macOS 13 Ventura or later, for example a 5K iMac from 2017 or later |
| Main computer | A Mac or a Windows PC | A Mac with Thunderbolt 3 or 4 on macOS 13 Ventura or later |
| iPad, iPhone or Android as the display | Yes, from the cheapest plan on | No |
| Second Mac's keyboard and mouse | Yes. While connected, the second Mac's keyboard and mouse can control the main computer | No. You use the keyboard and mouse of the Mac you work on |
| Trying it before you pay | Only when a promotional trial is available, according to Duet's help center. Subscriptions renew automatically | Yes: a free 7-day trial with all features, no account needed |
Duet facts from its iMac page (plans and prices), its help center articles on plans, subscribing, connecting two computers and Thunderbolt, its blog post comparing Duet with Sidecar, and its App Store listing. All checked on 11 October 2026.
What Duet Display is
Duet Display is an app from Duet, Inc., which describes its product as built by former Apple engineers. It started as a way to use an iPad as a second display and has grown into a whole family of features: second displays on iPads, iPhones and Android tablets, a remote desktop, a drawing tablet mode, and keyboard and mouse sharing between computers. It runs on macOS, Windows, iOS and Android.
Using another Mac or a PC as a display is a feature Duet calls Desktop to Desktop (on its iMac page it calls it "Duet Target Display Mode"). It needs the Duet Air plan or higher and a Duet account on both computers. The two computers connect over your network or, between two Macs on macOS 12.3 or later, over a Thunderbolt cable.
Where DisplayBridge is the better choice
DisplayBridge does only one thing, and it is built around it: using an iMac or another Mac as a display for your Mac over a cable. For that job, it wins on these points.
Full 5K instead of up to 4K
Duet promises "a retina display at 60 frames per second", and its own blog says it offers up to 4K resolution. I couldn't find any mention of 5K on Duet's website. On a 5K iMac, a 4K picture has to be scaled up to the 5120 × 2880 panel, which makes text slightly softer than on a real 5K display. DisplayBridge sends the full 5K picture at 60 Hz, uncompressed, so every pixel on the iMac is exactly the pixel your Mac drew.
One payment instead of a subscription
Duet Air, the cheapest plan that can use a Mac as a display, costs $3.99 a month, billed annually, which is about $48 a year. Over three years that is about $144. On the App Store the same plan costs $5.99 a month or $49.99 a year. Duet also sells a lifetime Duet Air license for $139. DisplayBridge costs $29, once, for the Mac you work on, and the iMac that shows the picture never needs a license.
No account, and a free trial every time
Duet needs a Duet account, signed in with the same account on both computers. Its help center offers a trial only "if a promotional trial is currently available", and subscriptions renew automatically. DisplayBridge needs no account at all, and every download is a free 7-day trial with all features. You test it on your own Macs and pay only if it works for you.
Sound on the iMac's speakers
DisplayBridge sends your Mac's sound over the same cable, so the iMac's speakers play it; you can also keep it on your own speakers or play it on both. Duet's website doesn't say anything about sending sound to the second computer, so the table leaves this row uncolored. If sound on the iMac matters to you, check it during a Duet trial.
Where Duet Display is the better choice
Duet covers many more devices and situations than DisplayBridge. It is the better choice if any of these apply to you:
- You want to use an iPad, an iPhone or an Android tablet as a display. DisplayBridge only works between two Macs.
- One of your computers is a Windows PC. Duet works with a PC on either side.
- You need a wireless connection. Duet works over your network. DisplayBridge needs a cable, because an uncompressed 5K picture needs about 10 Gbit/s.
- Your Macs are too old for DisplayBridge. Duet's connection between two computers works from macOS 10.14.4 Mojave. DisplayBridge needs Thunderbolt 3 and macOS 13 Ventura on both Macs.
- You want to control the main computer with the second Mac's keyboard and mouse. Duet allows that while connected. DisplayBridge doesn't pass keyboard or mouse input from the iMac.
- You also want a remote desktop or a drawing tablet. Duet Pro bundles these in the same subscription.
What "zero lag" means
Duet advertises "zero lag", and its Thunderbolt article promises "near-zero lag (<1ms)". That article also tells you to check the connection with a ping test, which shows what the number is: the time a small network packet needs to travel over the cable. It is not the time until a changed picture appears on the second screen. No display shows a picture with zero delay; a 60 Hz screen alone needs about 8 ms to redraw down to its middle.
DisplayBridge shows about 20 ms in the app, measured from the moment your Mac captures a frame until the iMac shows it. That is roughly 10 ms more than a directly connected monitor, which is unnoticeable in everyday use. Because the two numbers measure different things, the table leaves this row uncolored.
Setting up DisplayBridge
Install DisplayBridge on the iMac and on the Mac you work on, connect the two with a Thunderbolt cable or a 40 Gbit/s USB-C cable, and click Connect. The iMac then appears in System Settings as a second display, and you use it like any external monitor. There is no account to create and nothing to sign in to. This recording shows the moment it connects:
Both Macs need macOS 13 Ventura or later and Thunderbolt 3 or 4, which includes every 5K iMac from 2017 on, the iMac Pro, and recent MacBooks, Mac minis and Mac Studios. A USB-C charging cable won't work, even though it looks the same; look for the lightning symbol on the plug or "40 Gb/s" on the packaging. The setup guide walks through the two macOS permissions, and the six-minute setup video shows the whole process on my own iMac and MacBook.
Other Duet Display alternatives
- Luna Display: a $89.99 hardware adapter that turns an iPad or a Mac from 2011 on into a second display, also for Windows PCs. The picture is compressed, and a 5K iMac runs at 45 Hz or 30 Hz. My Luna Display comparison has the details.
- Sidecar (free, built into macOS): uses an iPad as a second display for a Mac. It cannot use a Mac as the display.
- AirPlay to Mac (free, built into macOS): wireless, with a compressed picture. For iMacs, the receiving Mac must be a 2019 or newer model or an iMac Pro.
- A hardware conversion kit: replaces the iMac's logic board with a driver board, so any computer or game console can use it as a monitor, but the iMac stops being a computer. See my conversion kit guide.
The comparison page lists all of them side by side.
Conclusion: which one should you choose?
If you want to use a 5K iMac from 2017 or later, or another Mac with Thunderbolt, as a display for your Mac, and a cable is fine for you, DisplayBridge is the better choice: full 5K at 60 Hz instead of up to 4K, $29 once instead of about $48 a year, and no account.
Duet Display is the better choice if you want to use an iPad, an iPhone or an Android tablet, if one of your computers is a Windows PC, if you need it wireless, or if your Macs are too old for DisplayBridge.
If you have two Macs with Thunderbolt, try it on your own setup: download the free 7-day trial; it needs no account.
Questions about this
Is there a Duet Display alternative without a subscription?
Yes. DisplayBridge costs 29 dollars once and uses one Mac as a display for another over a Thunderbolt cable. Luna Display is a one-time hardware purchase of 89.99 dollars. Apple's Sidecar and AirPlay to Mac are free and built into macOS. Duet itself also sells lifetime licenses; the Duet Air lifetime license, which includes Mac to Mac, costs 139 dollars, marked as 30 percent off.
Which free apps can replace Duet Display?
On a Mac, two free options are built in: Sidecar, which uses an iPad as a second display, and AirPlay to Mac, which sends the picture wirelessly to another Mac (for iMacs, a 2019 or newer model or an iMac Pro). Both compress the picture. DisplayBridge can be tested for free for seven days and then costs 29 dollars once.
Does Duet Display support 5K?
Duet's own blog says it offers up to 4K resolution, and its website doesn't mention 5K anywhere. DisplayBridge drives a 5K iMac at its full 5120 × 2880 resolution and 60 Hz.
How much does Duet Display cost for using a Mac as a second display?
Using a Mac as the display needs the Duet Air plan or higher; the cheaper Starter plan doesn't include connections between two computers. As of October 2026, Duet Air costs 3.99 dollars a month billed annually on Duet's website (about 48 dollars a year), or 5.99 dollars a month or 49.99 dollars a year on the App Store. A lifetime Duet Air license costs 139 dollars.
Can Duet Display use my iMac as a monitor over a cable?
Yes, over a Thunderbolt cable, if both Macs have Thunderbolt 3 or newer and run macOS 12.3 or later, and you have the Duet Air or Pro plan. Otherwise Duet connects over your network.
Does DisplayBridge work with Windows PCs or Android tablets?
No. DisplayBridge connects two Macs and nothing else. If one side is a Windows PC or an Android tablet, Duet Display is one of the options that supports it.
Do I need an account to use Duet Display?
Yes. Duet requires a Duet account, and you have to sign in with the same account on both computers. DisplayBridge works without any account.