The Data Documentation Initiative (also known as DDI) is an international standard for describing surveys, questionnaires, statistical data files, and social sciences study-level information.

Begun in 1995,[1] the effort brings together data professionals from around the world to develop the standard.

The DDI specification, most often expressed in XML, provides a format for content, exchange, and preservation of questionnaire and data file information.

DDI supports the description, storage, and distribution of social science data, creating an international specification that is machine-actionable and web-friendly.

The latest version 3.3 (also called "Lifecycle") of the DDI standard was released in 2020.