The FFIL extension is given to files that are used in the Mac OS X operating system. FILL files store a set of fonts. These can be TrueType or bitmap fonts. In the case of the latter, they need a PostScript outline font file to be fully functional. The FFIL font set is called a font suitcase because of its ability to store different fonts in a single file.

These types of files sometimes have the DFONT extension. They are stored in the System Fonts or Fonts folder.