Uniform Type Identifier
A Uniform Type Identifier (UTI) is a string defined by Apple Inc. that uniquely identifies the type of a class of items. Added in Apple's Mac OS X 10.3 operating system, UTIs are used to identify the type of files and folders, clipboard data, bundles, aliases and symlinks, and streaming data. Mac OS X's desktop search technology, Spotlight, uses UTIs to categorize documents.
UTIs use a reverse-DNS structure. UTIs support multiple inheritance allowing multimedia files to be identified as not as single type (as in MIME), but as all the types it is; An identifier can inherit from public.audio, public.video, public.text, public.image, etc.
The public.* domain is only editable by Apple and contains the base data types used by all UTIs.
Identifier | Conforms to | Comment |
---|---|---|
public.item | base class in the physical hierarchy | |
public.content | base class for all document content | |
public.data | public.item | base class for all files, byte streams, pasteboard, etc. |
public.image | public.data, public.content | base class for all images |
UTIs are even used to identify other file type identifiers:
Identifier | Conforms to | Comment |
---|---|---|
public.filename-extension | public.case-insensitive-text | Filename extension. |
public.mime-type | public.case-insensitive-text | MIME type. |
com.apple.ostype | public.text | Four-character code (type OSType). |
com.apple.nspboard-type | public.text | type. |
External links
- System-Declared Uniform Type Identifiers
- "Introduction to Uniform Type Identifiers", Apple Developer Documentation
- Ars Technica article on UTIs