Dfont or Datafork Truetype is a special type of TrueType font format, specifically developed for Macs running Mac OS X. You won’t find this file format on any other operating system.

In earlier Macintosh operating systems, such as System 9, files could store data in two entities called the resource fork and the data fork. OS X files no longer use the resource fork. A dfont is a TrueType font with the resource map stored in the data fork instead of the resource fork.

Dfont fonts have the file extension .dfont.

Dfonts on Macs running System 9

Earlier on this page I mentioned that dfonts are unique for OS X. This is true but for compatibility reasons it can be useful to convert Dfonts to regular TrueType fonts or back. A utility called dfontifier does exactly that. It can be useful if you still share documents with OS 9 users.

Dfonts on Macs running OS X

Some of the OS X system fonts provided by Apple are dfonts. These include Courier, Helvetica, Monaco, Symbol, Times and ZapfDingbats.

The problem with dFonts is that there can be naming conflicts with legacy PostScript or TrueType fonts. In case of duplicate font names, the dFont fonts should be removed to avoid text rewrap when using the incorrect font type. For prepress usage, it is common practice to use the PostScript versions of Helvetica and Times. In OS X versions up to 10.4 replacing the Dfont fonts by PostScript versions was no issue. With OS X 10.5 things are a lot more complicated due to its system font protection mechanism.