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macrumors bot
Original poster
Apr 12, 2001

While there are several apps designed to turn the iPad or iPhone into a secondary display for a Mac, the most popular options use Wi-Fi, which can render them all but unusable at times due to unavoidable lag. A new app from developer and former Apple Engineer Rahul Dewan aims to solve these lag problems with a tethered solution that turns an iOS device into a more reliable secondary display.

Duet Display, which is launching today, is the one of the first apps that transforms the iPad and the iPhone into an extra display for the Mac using a Lightning or 30-pin cable. By sending data over a cable instead of Wi-Fi, Duet Display is able to greatly improve on the lag is typically present when an iOS device is used as a secondary display.

Duet Display offers both a Retina mode and a non-Retina mode, along with options for 30 or 60 frames per second, and it's easy to install and setup, requiring just the Mac app, the iOS app, and a cable to connect the two devices.

The Duet Display app is inarguably an improvement over other options today, but it is not a perfect solution. As detailed in the video walkthrough of the app below, MacRumors experienced some issues when testing the app. On a 2012 Retina MacBook Pro, Duet Display's Retina mode caused a significant amount of cursor lag, rendering the app nearly unusable, and the CPU usage climbed to well over 200 percent.

The Duet website claims that all Macs using OS X 10.9 or later work with the app, as well as all iPads and iPhones, but MacRumors was unable to get the software to work with a 2010 MacBook Air running OS X 10.10.2. According to the developer, the issue was due to the 10.10.2 beta software, which does not work with the app.

Duet Display may not provide the perfect secondary display experience, but in our testing, we found that it was more reliable than current Wi-Fi options, and we believe it's a fantastic way to make good use of older iOS devices.

Duet Display for the Mac can be downloaded from the Duet website for free. The accompanying iOS app can purchased from the App Store for $9.99 for 24 hours, and then the price will go up to $14.99. [Direct Link]

Update 12PM PT: Some of our forum members have not been able to get Duet Display to work on an iPad running iOS 5.1.1, and the developer has asked people who want to use it with an iPad running iOS 5.1.1 to wait for an upcoming update before purchasing.

Article Link: Duet Display Offers Tethered Solution to Turn an iPad into an Extra Display for Mac [Updated]


macrumors 604
Mar 11, 2013
Seems like a great idea in theory, but I doubt Apple likes this, and like the article mentions, it is a less than stellar experience. I guess that's what external displays are for! ;)

Still, it'd be nice to have this capability in a bind.


macrumors 6502
Mar 22, 2010
Stupid idea for a problem that doesn't exist.
Btw why would you need 2 screens "on the go"? OSX solved this already with multiple desktops.


macrumors 68000
Apr 24, 2008
In that one place
Stupid idea for a problem that doesn't exist.
Btw why would you need 2 screens "on the go"? OSX solved this already with multiple desktops.

This setup allows you to feel important sitting at Starbucks with an Macbook Pro and an iPad Air. Your Facebook updates are now twice as engaging and interactive with your two screens.

Add your iPhone for the MacSreenOctopus for even more engagement!


macrumors 6502a
Oct 18, 2007
This is nice to see this sort of thing working over USB (previously worked over WiFi).

Would be nice if it could somehow worked over ThunderBolt, or if there was 1st party support from Apple for using the iPad as an external display over ThunderBolt. That would be a great feature to have in the rumored larger "iPad Pro". Imagine using a 15" Retina MacBook Pro with an iPad Pro on each side.


macrumors regular
Apr 30, 2008
Just installed it — works well on my MBP Retina Early 2013, even in Retina mode. BY "Well" I mean: seems to connect seamlessly as soon as I run the duet app on the mac, and response time seems very fast.

I'm not really going to use it at work since I have two Thunderbolt displays, but when I'm traveling or at home it'll come in very handy.


macrumors P6
Oct 23, 2010
Any plans to expand to Windows?

For those asking what's the purpose, this could come in handy for travelers who need a second monitor in a pinch. I often have a document on one screen and a document on another so I can refer back and forth when editing one of them.


macrumors 68030
Jun 2, 2010
Stupid idea for a problem that doesn't exist.
Btw why would you need 2 screens "on the go"? OSX solved this already with multiple desktops.

It doesn't sound like you're a road warrior. This type of setup comes in handy for those of us who travel that are used to multiple displays at home/work.

Spaces is nice; but Spaces is a fundamentally different solution since it does not allow you to view the content of two Spaces simultaneously the way you can with multiple displays.
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doug in albq

Oct 12, 2007
Expensive, buggy and virtually the same as Air Display except you need a wired connection. I am not sure why this is a news story.


macrumors 601
Oct 6, 2008
Stupid idea for a problem that doesn't exist.
Btw why would you need 2 screens "on the go"? OSX solved this already with multiple desktops.

As someone who works remotely, this app was built for me. I do software development and most of the time have Xcode open in fullscreen, with two panes on my main display and documentation/tasks/email open on another (virtual) desktop. At home I am fine as I use an iMac with a second display attached. While i'm working anywhere else I lose that ability. I've tried things like AirDisplay, but they are way too inconsistent and laggy, especially on crappy wifi networks.

Working at a hotel for example. Or at my works actual office space, which is in another state - I no longer have to be confined to a single display when working on my laptop.

I'm trying it out right now and it isn't perfect, there is a slight lag that you can definitely feel, but as a small secondary display for $9.99 on your existing iPad I don't see why people in this thread are complaining about this.

The multi-level marketing person who hangs out at starbucks every day isn't the only person who would use this app :rolleyes:


macrumors regular
Apr 30, 2008
Stupid idea for a problem that doesn't exist.
Btw why would you need 2 screens "on the go"? OSX solved this already with multiple desktops.

mmm let me think of a few scenarios common for me:
- working on stuff while watching email or task list on iPad screen
- developing and having documentation windows on iPad screen
- doing architecture modeling work - the current model I'm editing on the main screen, and other models I'm referencing on the smaller screen
- ... kind of an endless list really... did you really need to ask why multiple monitors can be useful?


macrumors 68000
Feb 29, 2008
Los Angeles
Stupid idea for a problem that doesn't exist.
Btw why would you need 2 screens "on the go"? OSX solved this already with multiple desktops.

Imagine being on the other side of the world moving from one hotel to another every few days. I doubt you'd opt to bring a monitor to accompany your laptop, but using an iPad as a secondary screen is much more realistic option.


macrumors 68030
Apr 20, 2008
Tried Wifi options before, horrible. Tempted to give this a go, give me somewhere to keep all my tools etc in Photoshop.

Think I read somewhere that touch works too?


macrumors 6502a
Oct 18, 2007
Stupid idea for a problem that doesn't exist.
Btw why would you need 2 screens "on the go"? OSX solved this already with multiple desktops.

How does it not exist? I've always wondered why there aren't any portable monitors on the market (edit: turns out I'm wrong [1]), and this aims to provide that. Also, this turns your iPad into a free external monitor for non-portable uses, too.

I'm sitting in front of 4 displays right now (15" rMBP + 3 externals). Virtual desktops are not an adequate replacement for multiple monitors. I don't have an iPad, but if I did, I'd use this on days when I spend a lot of time in a meeting room. I might even use it to add a 5th display to my setup if possible (so it wouldn't even be "on the go").

For what I do (software development with a bit of sysadmin tasks), the more monitors and more pixels the better. Hopefully some time in the future I will have a single massive curved display that engulfs my entire field of view, but until then, multiple monitors is where it's at.

For my non-software development uses, USB would be too slow for FCP X and probably Aperture (otherwise would be useful, I like to have video/photo full-screen on one monitor and browsing/timeline/settings/etc on another), but Ableton Live would benefit from a portable dual-monitor setup.

[1] Portable monitors do exist:
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macrumors member
Feb 28, 2013
I was waiting patiently for this but I must say it was very disappointing. Its a total CPU hog and its not as smooth as they make it out to be. When trying to scroll you end up dragging things around which gets really annoying. For simple viewing its fine but actual input and execution hasn't been too great for me so far. I've tried it on my iMac 27 and MacBook Pro Retina 15. I have an iPad Air 2 so my hope was that this would take advantage of the extra power somehow but doesn't look like thats the case. Hopefully the next few versions will make this better. My advice is.. wait a few versions because at this time its a quick money grab. Its not ready for prime time in my opinion. The CPU hog factor alone makes it a huge downer..


macrumors G3
Nov 26, 2007
IDK, handoff does well enough for my two screen needs. Not as seamless, but when I want to move Safari from my iMac's screen to my iPad... Well, you know how it works, I assume. Same deal with iWork apps and other apps that support handoff. Huge plus: allows me to use the iPad's CPU and GPU rather than having to the iMac's to run both displays.


macrumors 68030
Dec 30, 2010
Wow - so many people here are downers, or big time power users.

Many people could use a 2nd/external monitor. But, not enough money or desk real estate to have it all the time. This is a great idea for those that just need an occasional external monitor.

BUT - sadly, to check it out, you have to BUY the damn software and do way to return it.

Based on the CPU issues, I am debating about spending the $10.


macrumors 6502a
Mar 14, 2010
On 2014 rMBP 15 2.8 using 100-200% cpu usage. Fans going nuts. Not sure this is ready for primetime.
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