Uniform Type Identifier

A Uniform Type Identifier (UTI) is a text string used on software provided by Apple Inc. to uniquely identify a given class or type of item. Apple provides built-in UTIs to identify common system objects – document or image file types, folders and application bundles, streaming data, clipping data, movie data – and allows third party developers to add their own UTIs for application-specific or proprietary uses. Support for UTIs was added in the Mac OS X 10.4 operating system, integrated into the Spotlight desktop search technology, which uses UTIs to categorize documents. One of the primary design goals of UTIs was to eliminate the ambiguities and problems associated with inferring a file's content from its MIME type, filename extension, or type or creator code.^[1]

UTIs use a reverse-DNS naming structure. Names may include the ASCII characters A–Z, a–z, 0–9, hyphen ("-"), and period ("."), and all Unicode characters above U+007F.^[1] Colons and slashes are prohibited for compatibility with Macintosh and POSIX file path conventions. UTIs support multiple inheritance, allowing files to be identified with any number of relevant types, as appropriate to the contained data. UTIs are case-insensitive.^[2]