Acronym for ‘Application Programming Interface’. API software allows apps to communicate with each other, through the use of an interface. Simply put, it works by enabling one app to make a request to another app, which then provides them with a resource – data or some other functionality. A very common example is when a health app enables users to log in with their social media account password. When this happens, it not necessary for the app making a request to know how the app that provides the resource works. In doing so, however, the APIs may reveal user data to the resource provider. This is exactly what happened in the Cambridge Analytica scandal, where Facebook’s Open Graph API provided access to a third party on hundreds of thousands of users who had consented to sharing their data and, importantly, also indirectly on approximately 87 million who had not consented to such use.