In Mac OS and Mac OS X, what are file types and creators?

In Mac OS 9.x and earlier, every file has a type and creator code, which indicate what the file type and associated application. Each type and creator is a unique four-character code that identifies a kind of file or specific application. Based on this information, the Finder determines the icon to assign to a document, and which application to open when you double-click it.

Although type and creator codes are supported in Mac OS X, native OS X applications do not use them for new files. Instead, Mac OS X uses file extensions to identify a file's type (e.g, .txt, .jpg, .tiff). Additionally, Mac OS X allows you to choose which application opens a specific file or group of files. Modifying this preference leaves the type and creator codes of the file, if present, unchanged. For more, see In Mac OS X, how do I assign an application to open certain file types?

To determine or change the type or creator code of a file, use a utility such as the following:

Mac OS X

• Super Get Info (shareware, $20): An alternative to the Mac OS X Finder's Get Info command, Super Get Info allows you to view and change the type and creator codes of files.
• FileInfo (freeware): FileInfo allows you to view and change the file type and creator codes of files.

Mac OS 9.x and earlier

• Snitch (shareware, $20): Snitch is a control panel that gives you the ability to see and change a file's type and creator through the Get Info window.
• FileTyper (shareware, $10): FileTyper is a file-handling utility suite that allows you to view and change file types and creators, as well as create autotypers.
• TypesChange (freeware): TypesChange is a contextual menu plug-in that allows you to view and change the type and creator codes of files.

Below are a few common file types and creators. For a more exhaustive list, download a copy of the Type/Creator Database, a shareware program that contains thousands of file types and creators.

Also see:

• What is a forked file structure?
• In Mac OS or Mac OS X, how do I replace one icon with another?
• In Mac OS and Mac OS X, how do I convert a document into a format usable by a different program?
• In Unix, how do I use the MacUtils to encode or decode a document in MacBinary or BinHex?
• For Mac OS X, where can I download freeware, shareware, commercial software, and software updates?
• In Mac OS X, how do I assign an application to open certain file types?