Last year Dropbox announced a preview of the new Dropbox API v2. The new version simplified the Dropbox developer experience. In hopes to move toward a more simplified Platform, Dropbox announced deprecation of its Sync and Datastore APIs. Users already utilizing the Core API will be unaffected by the deprecations. The APIs will officially be retired on April 29, 2016.
The Sync API Library was originally developed to keep files in sync with Dropbox. The library was built on top of the Core API. Accordingly, now that the Core API is the base API Dropbox recommends to developers, the company encourages developers to move away from Sync to Core as a best practice. Further, multiple SDKs/APIs to accomplish the same functionality has caused developer confusion, which Dropbox aims to eliminate with the move to simplified options.
The official retirement of the Sync API was October of 2015. The retirement date of the Datastore API is April 29 of this year. Per usual, Dropbox encourages feedback and questions via the development forum and direct contact to the developer team
Disclosure: This article previously highlighted the deprecation of the Dropbox APIs, rather than their retirement. We adjusted the article to highlight the current news.