Requirements for Apps in the Windows Store

Microsoft has rarely imposed any significant constraints on the applications produced by their tools. User interface guidelines are also rare in the Microsoft arena. Early versions of Windows had some very general guidelines back in the 1990s, but they were not made detailed and prescriptive as the Windows ecosystem grew.

That is changing with Windows 8. With applications that will run on WinRT, which are currently called Windows 8 Style Apps, there are both firm constraints and detailed, prescriptive user interface guidelines.

During the beta period of Windows 8, you may have heard a different word used to describe Windows 8 Style Apps: “Metro.” This term was first used for Windows Phone 7. However, legal restrictions barred Microsoft from using the term in production for Windows 8.

The user interface design guidelines for Windows 8 style apps were discussed in chapter 13. This chapter concentrates on the technical and content requirements for app certification, which your application must meet to be deployed via the Windows Store.

The app certification requirements for Windows 8 are quite detailed. They are also expected to evolve steadily. This chapter will therefore not attempt to cover all the details. The URL noted earlier, http://bit.ly/Win8CertRequirements, should guide you to the most current version of the requirements.

However, this chapter summarizes some of the most important requirements you will need to know as you begin development of Windows 8 style apps. It's very important that you know and understand these requirements. When you place an app in the store, it is subject to being tested by human testers who will verify whether or not your app meets the requirements. If it doesn't, it won't be made available in the store.

In the section on “Checking to See if an App Meets Requirements,” you will look at the process you use for checking to see if you app meets the requirements. Some requirements are rather specific, and it's easy to see if you meet them. These can be validated before you attempt to place your app in the store. Other requirements are more general, and whether you meet them is open to interpretation once your apps have been placed in the store. However, you would be wise to understand those requirements and attempt to meet them before placing your app in the store.

Specific Requirements

Here are some of the specific requirements for an app to be certified for the Windows Store. This list isn't intended to be comprehensive; it simply highlights some of the requirements you will want to know about right away. You should still look at the entire set of requirements at http://bit.ly/Win8CertRequirements to become acquainted with the entire list.

Restricted APIs

Apps in the store can access only a restricted set of APIs. The certification requirements have the details, but you are basically restricted to a set of namespaces in the Windows 8 runtime libraries, a set of namespaces in the .NET libraries for Windows 8 style apps, and the Live Connect API for authentication.

This obviously means you can't use any version of the general .NET Framework libraries. Those libraries are intended for applications that run in the desktop mode.

Support for Windows 8 Interaction

Your app must support touch input to be certified, but this is usually handled by the controls you use to build the interface. More importantly, your application must not violate conventions for visual elements, including the bottom app bar and top navigation panel. Your app isn't required to use these elements, but if it does, it must use them correctly. For example, the app bar has to appear with a bottom swipe.

These requirements are easy to meet. One that's a bit harder is that your app must support a snapped view. This usually means special design for the view that is shown in the snapped view. Chapter 13 covered an example.

Performance Criteria

As you might expect, your app can't lock up. But it also can't run too slowly. The current certification criteria, for example, specify that the app has to start up in five seconds or less, and suspend in two seconds or less, even on a low-powered computer.

General Requirements

Some requirements are open to interpretation by the testers at the Windows Store. However, for the typical business application, it's unlikely an application would fail certification for such requirements.

Provide Customer Value

There are several listed requirements about providing value to the customer. Those requirements mean your app has to actually do something worthwhile, which means you probably won't be able to deploy a “Hello, World” app to the store. Also, if your app has a trial version, it has to look and act a lot like the full version.

There are a number of requirements that apply to any advertising you place in your apps. There are certain parts of Windows 8, such as the app bar, where you are not allowed to place ads. And of course, there are content policies prohibiting inappropriate ads.

Privacy and Consent

A number of requirements detail what you must do if you collect personal information. Certain privacy guidelines must be observed by your application.

Windows Store Apps also have some restrictions on the content they can access and display. As you might expect, there are restrictions on adult content, and on content that is discriminatory. Given the proclivities of some developers, it's worthwhile to mention that excessive or gratuitous profanity is not allowed. The Windows Store includes an age rating system, and your app is required to have an age rating that accurately matches your app.