We have a product which has various platforms: web, iOS, Android and Windows. The product has subscriptions too. The subscriptions can be purchased on web, Android and iOS.
Is it optional or mandatory to let the user to purchase these subscriptions from within the app?
(In case of App Store it was mandatory and in case of Google Play it is optional)
According to the documentation:
10.8.1
You must use the Microsoft Store in-product purchase API to sell digital items or services that are consumed or used within your product. Your product may enable users to consume previously purchased digital content or services, but must not direct users to a purchase mechanism other than the Microsoft Store in-product purchase API.
So users may use existing subscriptions, but should not be directed to a separate purchase mechanism to purchase the subscription.
Spotify, for example, has the same requirement but as it does not directly instruct users to purchase subscription via their website, just links to the user account page, it seems to be in line with Microsoft Store rules.