First Rule of Windows Store: There Are Rules to Windows Store

If you’re a developer targeting Windows 8 with a new Metro‑style app, you’ve got a lot of work ahead of you, not just in writing that app, but in conforming to a long list of app rules that Microsoft has devised. These rules exist for simple reasons: Metro‑style apps need to be safe, perform quickly, and work well, and they need to offer users a unique value of some kind.

For you, the Windows user, these rules are like the gold standard, ensuring that all of the apps you find on Windows Store–you know, the apps that are going to make Windows 8 better and better going forward–do what they’re supposed to do. And while a rote list of these rules would be mind‑numbingly boring, even to the most pedantic of developers, understanding what’s required at a high level can be very informative. Here’s what you can expect from the apps sold Windows Store:

Enterprises can get around this limitation, however, and “side‑load” apps to their users through secure portals as well.

• Windows Store only : Microsoft only allows Metro‑style apps to be acquired and updated through Windows Store. Developers cannot offer these apps (or app updates) separately, from the web, or through other means. This allows Microsoft to control the quality of apps for Windows 8 and to enforce the rules that follow.

• Free and paid: Windows Store caters to both free and paid apps. Those paid apps can range in price from $1.49 on up (in the United States).

• Trial versions: App makers can optionally provide a trial version of a paid app. That trial version of the app has to provide a reasonable approximation of the full version and cannot simply be an ad for the paid app. Trial versions can be time‑limited or feature‑limited.

• In‑app purchases: Apps can optionally offer in‑app purchases, which are optional paid features.

• Advertising: Apps sold by Windows Store can contain advertisements. These ads can include offers for in‑app purchases, offers for the full version of the game from the trial version, and so on. Apps cannot, however, exist solely to serve ads. And apps cannot serve ads on their live tile, app bar, or via the edge UIs.

• PCs and devices: The same Windows 8 apps can run on both traditional PCs (e.g., Intel x86) and new Windows RT‑based (ARM) devices. However, app makers are not forced to support both, and you will see some apps that run only on one platform or the other.

In this context, a PC is a PC based on an Intel or Intel‑compatible chipset, and a device is a PC that’s based on an ARM chipset and running Windows RT.

• 5 PCs/devices: Apps you purchase or install from Windows Store can be installed on up to 5 PCs and/or devices.

Apps must be rated and conform to rules set forth by the ESRB or equivalent rating system used in your locale.

• Content policies: Windows Store enforces strict content policies that can vary from region to region. No apps with a rating over ESRB (Entertainment Software Rating Board) Mature (or equivalent) are allowed, which excludes adults‑only content (that which features prolonged scenes of intense violence or graphic sexual content).

• One tile: If you’ve ever installed an old‑school Windows application like Office or Visual Studio on Windows 8, you know how awful it is to have numerous application tiles spewed onto your Start screen at the end. This won’t happen with Metro‑style apps: Developers are limited to adding just a single app tile to the Start screen.

• Metro‑style apps only: Apps sold via Windows Store must be real Windows 8 apps–that is, Metro‑style apps and not traditional Windows applications. That said, Microsoft is allowing developers to list their desktop applications in Windows Store, though directing users who wish to learn more, download the application, or purchase it, to do so from the developer’s website.

• No websites allowed: An app must be a native Windows 8 app and not just a shell for a website. Windows 8 provides a facility for pinning favorite websites to the Start screen already.

• Respect privacy: If an app needs to publish your personal information to a third‑party service, it must provide an opt‑in mechanism so that you, the user, can explicitly OK this behavior before it happens. And the description provided must accurately explain how the information will be used or share and provide a way through which you can later rescind your permission. Apps that collect personal information must provide a privacy policy that explains how the developer is safeguarding your information.

• Secure: Apps cannot compromise the security or integrity of Windows. Put simply, they can’t be malware or link to malware.

• Reliable: It sounds fairly obvious, but apps must be reliable and not stop working suddenly, end unexpectedly, or contain what Microsoft calls “programming errors.” Ignore the irony of that statement for a moment and consider why this is truly important: When you download an application from the web, there’s no quality guarantee at all, and if the application stops working or never works properly, you have no real mediation other than complaining to the developer. In Windows Store, there are community‑based means of complaint–poor reviews and ratings in the store–and Microsoft, as the curator of the store, to complain to as well.

• Performance: Microsoft calls Metro‑style apps fast and fluid, and it means that. Put in real‑world terms, apps must start up in 5 seconds or less and resume in 2 seconds or less. Not impressed? Those scores must be obtained on a low‑end, Atom‑based PC. Chances are the Windows 8 device or PC you’re using is much faster.

• Windows 8 features: Apps must support key Windows 8 features, including Snap, in which the app can share the screen with another snapped app. Apps must respect and utilize the system‑level methods for app closing and not provide their own buttons or other mechanisms for closing. If an app uses notifications, it must support the system settings for these notifications so that the user can externally configure whether they work.

• Network‑friendly: Thanks to a new emphasis on cellular connectivity in Windows devices and PCs–or what Microsoft calls metered Internet connections –apps must prevent users from unintentionally transferring large amounts of data over such networks. Typical examples include apps that provide streaming video or audio, both of which have specific transfer limits.

• Multiple markets and languages: Apps can be sold in multiple markets and in multiple languages if desired, though they must only support one of each.