SharePoint has, for the better part of its history, been very supportive of customization and providing access through the use of APIs. This, in turn, has resulted in numerous ways that help developers to read, write, and modify data stored within SharePoint, regardless of whether this is SharePoint Online or an on-premises SharePoint server.

Before SharePoint Online was available, the APIs within SharePoint were where mostly older SOAP-based web services reside under the /_vti_bin/ virtual directories in SharePoint. One such older web service is listdata.svc, which is located under /_vti_bin/listdata.svc. Although some of these are still available even with SharePoint 2016, one should not rely on them, as they are mostly provided for backward compatibility and either deprecated or a newer (and typically better) interface is available.