OpenType is a font format that was collaboratively developed by Adobe and Microsoft during the 1990s. The first specifications were published in 1997, and the first OpenType fonts came onto the market in 2000. Today, most new fonts are released in OpenType format, which can safely be considered the new industry standard.
The OpenType format supports Unicode™, which is why OpenType fonts can contain large character sets. In fact, an OpenType font can contain more than 65,000 glyphs! This is a considerable increase in character set size over past formats; most PostScript and TrueType fonts could only contain 256 characters.
Unicode-support gives OpenType fonts much better language support opportunities than PostScript or TrueType fonts have available. Instead of one font for each language group (Western Roman, CE, Baltic, etc.), OpenType character sets can include all of these code pages in one single font. In addition to Western characters (ISO Latin 1, etc) and their accents, common additional characters include Central and Eastern European, Cyrillic, and Greek. Some fonts may even include Chinese, Japanese, Korean, Hebrew, or Arabic. Fonts for languages that are written from right to left (i.e., Arabic) may require special applications and/or system support in order to function properly.
OpenType makes advanced typographic and language dependent features easily available to all users. For instance, the advanced typographic features in OpenType fonts commonly include a wide range of special glyphs, which can include ligatures, titling and swash characters, old style figures, small caps, fractions, and historical glyphs. In the past, each of these so-called “Expert” character sets had to be packaged in a separate font file, making the setting of advanced typographic features cumbersome.
Major operating system manufacturers have put a lot of effort in making OpenType fonts work in new, as well as some older, versions of their software. But it is important to remember that not all OpenType features are available in every application; some applications are not yet OpenType-savvy, as support of OpenType fonts is highly dependant on the applications’ level of Unicode support. Adobe InDesign, as well as Illustrator and Photoshop CS, support multiple codepages and advanced typographic and layout features. The newest versions of Microsoft Word, Quark XPress and CorelDRAW are OpenType-savvy as well. OpenType fonts may still be used in applications that are not OpenType-savvy. However, in these applications, only the first 256 characters of the font’s character set will be accessible (this is the basic character set for Western Roman languages). Unfortunately, in these cases, the extended language or typographic support of the OpenType font will not be usable. Users of non-OpenType-savvy applications, such as older versions of Adobe and Quark products, as well as most Macromedia products, may wish to keep using PostScript or TrueType fonts until they upgrade.
The OpenType format simplifies font management and the publishing workflow by ensuring that all required glyphs for a document can be contained in one cross-platform font file that can be used throughout the entire publishing workflow. Applications and operating systems can also verify the source and integrity of OpenType fonts because there is a digital signature within every font. This helps reduce font piracy.