Cloud app vs. Web app -- what's the difference?

What's the difference between a cloud app and a Web app? Gabe Knuth explains the difference between these similar terms and asks readers to share their input on the distinction.

As a sort of spiritual follow-up to Brian Madden's article called Saying "the PC is Dead" does not mean "the keyboard and mouse are dead," I'll touch on another misconception: the idea that cloud applications are the same as Web applications.

The terms cloud app and Web app are used interchangeably, but I think it's time to define them publicly and have the discussion about these terms. (I'm just as guilty as the next guy, even though I try to be aware of when I use each term.)

First let's explain what we mean by cloud in this situation. When we refer to cloud, we're talking about an architecture that has the data and the majority of the compute cycles happening in a data center somewhere. All of that is supported by a sophisticated back end that ensures uptime, security, integration with other systems and supports as many access methods as necessary. Cloud can also be public or private, and sometimes cloud refers to solutions that aren't labeled "cloud."

On the surface, Web apps share some of the same characteristics. They're located elsewhere and are accessible from almost anywhere. Web apps help you access cloud services, but that doesn't mean they're the same. They can be standalone things, too, like apps that allow you to convert bitmaps to vectorsadd drop shadows to images or find out who's stopped following you on Twitter.

Unfortunately, there's no logic puzzle that says all cloud apps are Web apps, but not all Web apps are cloud apps.

Box, Dropbox, ShareFile, Sugar Sync -- these are almost universally considered cloud apps and, while they have a Web interface, they are in no way Web apps. They run on back-end systems designed to scale and support many users with different requirements. A Web interface is just another way to use these services.

Email, in all its boring, spam-filled glory is also a cloud app. In fact, it was a cloud app back when it was called E-Mail or whatever T. Herman Zweibel would call it, even though we didn't know it. We use Outlook, Mail.app and other mail apps that allow us to access our email stored in Gmail (widely considered a cloud app), Exchange (almost never considered one), Zimbra (if you work for VMware) and all the other back ends out there.

We could look at SalesForce.com and see that it is accessed primarily over the Web, like many other solutions that could be considered Web apps, but if the access method is what determines the classification of the app, then you can't ignore the mobile apps designed to make it easier to use SalesForce or an expense tracking and travel system like Concur (which owns TripIt).

On second thought, maybe calling everything accessed via the Web a Web app is OK, as long as we look at it as a multi-tiered approach where the service, running in the cloud, is accessed by an app, wherever that app may be.

We have mobile apps, desktop apps, Web apps and so on, all accessing services that exist elsewhere. Maybe there is no such thing as a cloud "app" and we should be using the term cloud "service" exclusively. What do you think?

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About the author:
Gabe Knuth is an independent industry analyst and blogger, known throughout the world as "the other guy" at BrianMadden.com. He has been in the application delivery space for over 12 years and has seen the industry evolve from the one-trick pony of terminal services to the application and desktop virtualization of today. Gabe's focus tends to lean more toward practical, real-world technology in the industry, essentially boiling off the hype and reducing solutions to their usefulness in today's corporate environments.

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