OpenType

All Durotype fonts are OpenType fonts. OpenType fonts are cross-platform fonts which can be used in both Windows and Mac OS X.
       An OpenType font contains either PostScript or TrueType outlines. So there are two ‘flavors’ of OpenType fonts: a PostScript flavor and a TrueType flavor. OpenType fonts containing PostScript outlines have an .OTF extension in the font file name, while OpenType fonts containing TrueType outlines usually have a .TTF extension.
       Durotype produces only PostScript flavored OpenType fonts. This font format can be used with Windows (2000 or later) and Mac OS X (not Classic Mode under Mac OS X). Note that no additional software has to be installed to use OpenType fonts with these operating systems, because they provide native support for OpenType fonts.

Unicode

All Durotype fonts are Unicode fonts, i.e., all Durotype fonts support Unicode. Unicode is a system of numbering the characters in a font — which supports more than the traditional maximum of 256 characters per font.

Limitations of Older Operating Systems

Windows (2000 or later) and Mac OS X support Unicode fonts. Older Windows and Mac operating systems (including Classic Mode under Mac OS X) do not. When using Durotype fonts with these older operating systems (with ATM Light, a free system software component from Adobe), only 256 characters of the font’s character set will be accessible (this is the basic character set for western languages). Although it may be possible to use Durotype fonts with these older operating systems, Durotype does not support this.

Limitations of Older Applications

Many older applications do not support Unicode fonts. When using Durotype fonts with these older applications, only 256 characters of the font’s character set will be accessible (this is the basic character set for western languages). See the user manual of your application to check its Unicode support.