What is the difference between an MS office app and MS office add in

Question

I was trying to find a way to publish an outlook add in to office store. But I found out that we can publish only office apps and not the add ins to the office store. Hence I wanted to know what is the difference between an office app and an office add in? And is there an easy way to convert an already built add in to an app? Or will I have to implement the functionality all over again, while developing the app?

Answer 1

Hence I wanted to know what is the difference between an office app and an office add in?

Not so long ago (at #build2015) MS named Office Apps as "add-ins" as well. Classic Office add-ins are based on the IDTExtensibility2 interface (COM). They can't be run on any device or web browser. Office COM add-ins are for the desktop editions of MS Office (x86 and x64). COM add-ins can be implemented using a wide range of programming languages: from unmanaged C++ or Delphi to managed ones (C#, VB.NET and etc.). On the opposite side Office Apps (also called as add-ins now) are a small web based applications (HTML, CSS, JS) that have a limited access to the object model (typically related to the selection or opened item).

And is there an easy way to convert an already built add in to an app?

No, they are entirely different type of applications.

Or will I have to implement the functionality all over again, while developing the app?

Yes, you need to develop an Office App from the ground.

It is not lear what Office application you are talking about, but in case of Outlook you may find the Selecting an API or technology for developing solutions for Outlook 2013 article in MSDN helpful.

Answer 2

Sorry for the confusion. "Add-in" is just the new name for "App". So, you should be able to publish your add-in (built using HTML and JavaScript) to the Store. This is different from the really old COM add-ins.