The pre-order feature is listed in a new iTunes Connect Resource and Help document, which was discovered this afternoon by MacStories. The document says that developers are able to "make new apps available for pre-order on all Apple platforms."
Customers can see your product page and order your app before it's released for download. Once your app is released, customers will be notified and your app will automatically download to their device. For paid apps, customers will be charged before download.Apple outlines the specific steps developers will need to take to list an app for pre-order, which includes navigating to the Pricing and Availability section of iTunes Connect, choosing "make available for pre-order," and submitting an app for review.
To be made available for pre-order, an app must have a release date at least two days in the future, but no more than 90 days in the future. Pre-orders are available for both free and paid apps.
When an app is pre-ordered, on release date, it'll be automatically downloaded to a customers device. With paid apps, the purchase price will be charged when the app is released, not before.
As our sister site TouchArcade points out, there are already two apps available for purchase using the new pre-order feature. Both Gorogoa ($4.99) and Inside (Free) can be pre-ordered from the App Store ahead of a release coming later this week.
Apple today also announced the general availability of introductory pricing for subscriptions, allowing developers to charge less for the first few months of an auto-renewing subscription. This is a feature that was initially introduced in iOS 11.2.