Really, what is an 'app' on Windows? Microsoft's Universal App Model answers that question

It's surprising, but Windows has never had a definition of an app. "You know it when you see it, but it's never written down," said Andrew Clinick, Group Program Manager at Microsoft, during his session at Build 2016. Nothing was really defined, but there were a bunch of guidelines over the years. According to Microsoft, it's been very difficult to actually build an app model, and it hasn't been really enforced.

Universal Windows App Model

If we try to trace the journey, we know it all started with .exe but we've never had the answers for how does one install it, how do you store state, how long does the app run for, how do you integrate with the OS or with other apps, and so on and so forth.

This is why we need an app model, and the Universal Windows Platform (UWP) App Model attempts to answers these questions.

The Universal Windows App Model is unified across all Windows devices scaling from IoT to Mobile to PC to Xbox to Hololens. It defines the complete app lifecycle for all apps on Windows, from cradle to grave – Install, Runtime environment, Resource Management, Update, Data Model, and Uninstall.

Project Centennial

While the app model is inclusive of all apps that run on Windows, and is focused on Universal Windows apps, developers have to run existing apps, be they for phones, Windows 8.1, or classic Windows. Project Centennial allows developers to convert classic Windows applications to Universal Windows apps and aims to define the app model for classic Windows Apps since until now there has been no systematic definition of an app on Windows.

You might be wondering why is there a need for an app model for desktop now. The vast majority of the problem is registry growth and fragmentation. Your PC accretes more and more into the registry and file system over time leading to Windows rot. Also, as every one of us has experienced – consumers and developers – a true 100% uninstall is almost impossible to do. You're left with files and registry junk and other bits all over your system.

Modern Software Installer

In 2015, Microsoft introduced .appX as the common installation package for UWP apps, enabling PC, Phone, HoloLens, and IoT to all use the same technology. Microsoft is now expanding the installation technology to be even more inclusive with existing Desktop apps and Xbox. The November 2015 release expanded where you can use .appX and enabled, by default, installing from anywhere and not just the Windows Store. Prior to this, you could sideload from anywhere, but that required PowerShell geekery.

Microsoft's ambition is to make .appX the ultimate installer across the Windows ecosystem. While MSI is almost certainly not going away any time soon, the new app model allows you to bring in a new suite of features to your apps — like integrating into Cortana, and other apps — while bringing your code along without any significant change.

At Build 2016, Microsoft announced that the company is investing to make the modern installer the de facto installation stack on Windows. At this moment, it does not have all the capabilities of MSI or ClickOnce, but the idea is to improve with time. This will give a full platform for building install experiences, enabling great install experience from both Windows Store and custom distribution channels, enabling desktop apps to be converted to be installed, and enabling extensions platform.

The Bottom Line

With Windows 10, Microsoft is turning a new leaf and the Universal Windows Platform App model brings a cohesiveness of the Windows ecosystem across devices. It defines a clear deployment model and provides a better way to install/uninstall and update the application. While this improves app hygiene and consumers benefit from expected app behavior and familiar user experience, it also helps in keeping Windows healthy and avoid the rot with time.

  • How many times they are re writing this bottom line
  • Bottomless pit is more like it
  • "Where are the apps on mobile?" rants starts in 3,2,1....
  • Where are the apps on mobile? I don't see any, do you?
  • I have 180+ apps and games combined and really dont need a lot more Sent from Windows Central Universal app on Lumia 1520
  • Agreed. Android and iOS users should get a life, their pride over thousands of useless apps doesn't make sense.
  • Not when most of the apps do the same thing.
  • But also ton of useful apps that doesn't exist on WP. Posted via the Windows Central App for Android
  • Yeah.  Because they're all useless. /s The simple fact is, there are no particularly good apps on Windows 10 mobile.  There are plenty of good enough apps, plenty more apps that are equivalent to their counterparts on iOS and Android, but not a one, that I am aware of, at least, that is better than what is found on the competition. And until there is, there is simply no reason -- none -- to use a Windows phone, other than dislike for Google and Apple. (Which, BTW, is why I use a Windows phone.)
  • I have about 53 apps on my phone (L640 on 8.1). The only app that I wish we had on Windows is Strava (cycling and running tracker). I'm using Run the Map and I can send my activity to Strava which isn't a total loss. I then check out my activity on Strava on my Apple phone which is basically an iPod for me now. ~~Just a flat-out high speed burn through Baker and Barstow and Berdoo.~~
  • I use Runtastic for running and cycling
  • Yep
  • UWP is like that custom lockscreen API that was released on 8.1, nobody cares, nobody uses, the concept of UWP failed as well as the hype of WP enthusiasts that devs would be crazy to develop to WP when uwp came out, but still, no one cares about WP or uwp apps
  • Thanks for speaking for everyone.  It amazings me how valuable some people truly think their opinion is.
  • Hyperbole aside, everything he said is very nearly an objective fact. Where are all the great lockscreen apps?  Where are all the great UWP apps?  Where, for that matter, are all the people buying Windows phones? I'll tell you where: Nowhere.   So far, UWP is a bust.  And that's a fact.
  • Hard for anyone to dispute any of this.
  • Add to that: Who picked up the health platform which the band showcases? Nobody. And who uses their iot platform? Also nobody. And who will use their bots platform? Also nobody. Google and Facebook will easily win this because they have the users. The whole ******* world hates Microsoft except me and a few chickens. What Microsoft should really do is epically rebrand. Sent from an alien space ship with a Lumia 950
  • At least someone is enlightened enough to see the reality, thank you
  • You don't have any facts to back that up. We just had an article a few days ago about Game Troopers who stated point blank that Windows (including mobile) has been good and profitable to them and provided the numbers to confirm it. I wish that people who don't like the concept of UWP apps would stop trying to speak for everyone else.
  • I love the idea of UWP with Windows 10 and mobile. I may feel a little down from recent articles and windows 10, but what's the point?
  • Biggest issue is that it is still not as capable as w32. So why build your app in a new API? Next, the API is growing and changing. Most people know Redstone 2 will be the point where it reaches maturity. Why write code and then have to go back in and change things based on MS's changes. Then there's the fact that it's relatively new so if people do want to write for it, you likely won't see these Apps for a while. It even takes a huge company like Facebook quite a while to develop an app. Nevermind small companies juggling multiple platforms.
  • The API hasn't changed, it's grown yes, but not changed.
  • And you base your statements on what ?
  • Cool story, bro. Go take some more shirtless pics.
  • Maybe he is broke and has no money to buy a shirt. Even the camera is black and white.
  • It is very clear that you are definitely know knowing nothing about uwp.. Windows 10 Mobile
  • Universal won't be "Universal" without MOBILE. Focusing on US? Where if you don't have an "i" in front of your device ur ****? Why does Microsoft forget that rest of the world.exists too. Apple n android both focus on the world. Be it Bing or Cortana, Microsoft fails to reap what it sows and then apple "reinvents" it n sells it like pancakes. Someone should really sack the worthless marketing guys they have.
  • Apple tries to get market share where its low... Microsoft works in different way, if market share is low in one country, they ignore that country and make it more worse!
  • Are there currently any apps outside the Windows Store (browser downloadable), that use the APPX installer? Sent from a shiny electronic rectangle.
  • Stores should make sure apps can be trusted... There aren't any iOS apps outside the Apple store and the ones outside google play I wouldn't want them because they could contain dodgy code... Hell, even in google play there are apps you don't want on your device...
  • I don't really need MS to police my PC thanks. I have my own brain.
  • Right now? Probably not (m)any.  Double click installation of appx isn't something that will come to the public until the Anniversary release of Win 10.  You can still install via appx but it requires powershell commands to do it so it's not a particualrly friendly distribution format at the moment.
  • In the build screenshot, you see the app "paintnet" installer. Is there any link for it?
  • It could be Paint.NET.
  • I know, but is there an app of? On the screenshot, it shows that there is an app of that
  • nevermind, found the video ( It is just an 'installer'
  • I like that UWP makes you torrent a file from a desktop, mobile and even your XBOX.
  • Actually interested to see how appx fares. Want to see people distribute installers like that.
  • In light of the retrenchment, I really think MS also needs to focus on making web apps work really, really well on Edge, especially mobile. Those web notifications are a good start, but we need more with things like background processes.
  • This! The Web is the only truly universal platform, and a superb browser can go a long way toward mitigating the app gap.
  • If MS will ditch phones, there will be no purpose of UWP and no need for Windows ecosystem "acros devices". What devices? Windows is - for now -- neither in smart TVs, nor in smart cars etc. MS Windows will stick in PCs with uncertain future 
  • MSFT nor their OEMs won't ditch phones because of the ecosystem... MSFT wants to get into the living room via the Xbox also running uwp apps. Eventually they'll get there but building an entire ecosystem takes time and we could admit that they were kinda late to that party.... Still I think they're catching up...
  • OEMs care about selling devices. The few that are around won't last long with current sales, especially current OEM sales. They only have like .01% of the market and there isn't much hope of that increasing this year. Posted via the Windows Central App for Android
  • you should really give me your magic crystal ball to see how sales will go... I'm sure MSFT will try to push their OEM partners as much as they can to get Windows 10 Mobile powered phones out to the people, be it consumer or business users...
  • You don't need a magic ball. Just look at the trends. OEMs have never released a successful Windows phone and Microsoft has done nothing to change that in the near future. If Microsoft is pushing them, there is no sign. Phones don't seem to be coming and the ones that are available are flopping hard. Like I said, you don't need a magic ball.
  • I hope and wish you are right. What I wanted to say is that if MS fails with phones, the plan of having ecosystem across devices will fail too. Xbox will not save it as there are no other devices.
  • You don't need a crystal ball to see it, the writing is on the wall... OEMs will not be able to pick up the slack that has been left by MS's retrenchment... Nobody is waiting for an OEM phone... almost everyone (who is still interested in WP) wanted a Lumia... or may be a Surface phone if it launches... And especially given that MS has said that their focus is US, UK & Western europe, its hard to see them make any dent when India, Brazil & China are not a focus market for them...
  • It would appear this is one of the reasons (not the only reason, they also want to focus on what Panay's team is doing) MS has killed the Lumia line -- to encourage OEMs.
  • I'm not sure whether they're available in other coutries or not, but Microsoft has been in several brands of "smart/connected cars" for over a decade now. Almost every car with touch screen navigation or radio runs "Windows Embedded Automotive". Ford Expeditions are one example. From what I can gather, they're planning on changing that to Windows 10 IOT... whenever that might be ready. 
  • It's all great but Microsoft making huge mistakes in my opinion,first not allowing devices with 512mb of ram to upgrade to windows 10 even that they work just fine even still much smoother than many androids with 1gig,second no commercials at all while on other hand google and apple commercials are everywhere, and last but not least they should pull out all Microsoft apps from google store since there is no single google app in windows store (official google apps)
  • MSFT could have had commercials non-stop, 24/7, and still not make any profit. There's no way Windows phone could go head-to-head with iOS and Android. Too late in the game. MSFT is now shrinking their smartphone biz. I don't blame them. Why throw away good money chasing the two front runners when you know you'll never catch up? Windows phones from now on will be a niche market for consumers and tools for business use. ~~Just a flat-out high speed burn through Baker and Barstow and Berdoo.~~
  • What's the difference between program and app?
  • There's plenty of differences but they're mostly in the background. It all has to do with how they're built, such as the API's and tools they use, how they compile and execute, how they're run, how they handle resources, how your system handles them, even to uninstallation. There's also integration to consider, and how closed off they are. Windows Central for Windows 10-Nokia Lumia 830
  • Good informative article Abhishek.
  • This is a potential platform
  • Windows devices rocks..!!! There are problems, but still its the best in terms of productivity
  • "App जाएं भाड़ में मुझे नए windows phone चाहिए यार.....कब से wait कर रहा एक mid range Lumia का......" सुन रहे हो Microsoft वालों ।
  • I would like to see this platform evolve because it still feels slow, not integrated with the rest of the os, and lacks advance features found in the .exe apps
  • I work on a Winforms app with 400+ screens and 4.5M lines of code behind it.  A decade ago we seriously considered re-writing the entire thing with a WPF front-end.  Where did WPF end up?  I can't see me pushing this "app"-lication to the UWP any time soon.  I'm just not seeing the benefit with this for large-scale LOB applications, as opposed to migrating the entire thing to a responsive, browser-based front-end.
  • 70% of android and ios apps are junk...
  • MS is really going all-out for UWP... I hope they have backup plan, should it fail.