Methods, systems, and computer-readable media for transforming validated user interface layouts using inter-platform design mapping data are presented. A computing device may load source mockup data defining a first validated user interface layout associated with a first set of user interface design guidelines. Subsequently, the computing device may load interface mapping data defining relationships between first user interface elements associated with the first set of user interface design guidelines and second user interface elements associated with a second set of user interface design guidelines different from the first set of user interface design guidelines. Then, the computing device may transform the source mockup data based on the interface mapping data to produce target mockup data defining a second validated user interface layout associated with the second set of user interface design guidelines. Thereafter, the computing device may store the target mockup data defining the second validated user interface layout.