Crystallographic data exchange format developed by the International Union of Crystallography (IUCr); contains categories of crystallographic data used for archiving and distributing purposes.

The format was adopted in 1990 as a standard file structure and is regularly used for reporting crystal structure determinations. The CIF file contains data categories, such as _audit_, _atom_, _cell_, _database_, and _refine_. These categories contain information, including the CIF creation, atom type properties, cell parameters, data specified by the database managers, and data describing structure refinement parameters.