Acronym for ‘Software development kit’. SDKs are external packages that can be injected into the code of an app that facilitate the creation of specific functionality, such as analytics and different monetization options. SDKs provide a shortcut for developers, so that they do not have to start coding from scratch. The third parties that share SDKs with developers may use these to gather data on users. This is for example what had happened when it was discovered that Facebook was collecting data through period tracking apps.