These endpoints are part of our original plans: Starter, Basic, Core, and Plus. They will remain entact and usable for users on these plans. As a user of these APIs you will still get new providers, support, and any core extraction algorithm updates. There will however, be no additions to the response attributes or major version updates to the endpoint. If you are interested in checking out some of the latest and greatest APIs, read about Products.
The preview endpoint was built to allow users to customize embeds. If you are building something similar to the Facebook status message update functionality, then this endpoint is for you. It returns multiple images, objects, and embeds to choose from when creating an embed.
Read the Preview API