While I'm well aware there is no API to directly post content to instagram, many apps I've seen have found a workaround through using the Instagram Sharing to Feed functionality via Android Implicit Intents and iOS Custom URL Schemes or Document Interaction.
My question is, would it be possible to create the same UX on a mobile website? The idea would be that user would click a App Link in their mobile web browser that opens their instagram app to share the content.