GIFTI

GIFTI is an open file format designed for storing and exchanging surface-based neuroimaging data. It is commonly used to represent cortical and subcortical surface meshes and any data defined on those surfaces, such as curvature, thickness, labels, or functional measurements mapped to vertices. The format emphasizes interoperability among software tools.

A GIFTI file consists of an XML header that describes one or more data arrays. Each data array carries a data type, an intent that indicates the semantic meaning (for example, coordinates of vertices, faces/triangles, or per-vertex scalars), and a storage payload containing the actual numerical data. Data can be stored as binary or ASCII within the file, and in practice is often compressed for efficiency. The header can also include metadata and provenance information.

GIFTI files typically use the .gii extension (and may be gzipped as .gii.gz). They are designed to be read alongside other neuroimaging formats such as NIfTI, allowing software to import or export surfaces and associated measurements. The format is supported by a range of neuroimaging tools and libraries, including dedicated surface visualization tools and neuroimaging pipelines, enabling researchers to share standardized surface representations.

Developed to facilitate interoperability and data sharing across platforms, GIFTI remains widely used in the neuroimaging community. References and documentation describe the structure of DataArray elements, data types, and semantics used within the format.