Rich Text Format (RTF) is a document interchange format created by Microsoft for transferring formatted text and graphics between applications and operating systems. The specification summarizes its purpose directly: the RTF Specification “provides a format for text and graphics interchange that can be used with different output devices, operating environments, and operating systems,” so that “documents created under different operating systems and with different software applications can be transferred between those operating systems and applications.” Its defining trait is that all of that formatting is encoded in plain ASCII text rather than in an opaque binary file.
An RTF document is built from control words and groups. Control words are backslash-prefixed tokens such as \b for bold, \i for italic, \par for a paragraph break, or \fs24 for a font size, and groups are delimited by curly braces that scope formatting. A document begins with header tables — a font table, a color table, and a style sheet — and then a body of text interleaved with control words. Because the whole file is readable text, an RTF document can be generated, parsed, and edited by simple programs, and it survives transmission through systems that would mangle a binary file.
RTF was introduced by Microsoft in 1987 and evolved through a series of versioned specifications over the following two decades, adding support for Unicode, tables, embedded objects and pictures, revision marks, bidirectional and East Asian text, and many other features as word processors grew more capable. The specification was published openly by Microsoft and is preserved in the Microsoft documentation archive, which is what made RTF practical as a common target that any application could read and write.
For much of the 1990s and 2000s, RTF served as the practical lingua franca for exchanging styled documents. When two programs could not read each other’s native formats, RTF was the safe common denominator: word processors, email clients, help-authoring tools, and report generators across Windows, classic Mac OS, and other platforms could all import and export it. The Windows clipboard and the rich-edit control used RTF as their formatted-text representation, embedding the format deep in the operating system’s text handling.
RTF’s importance lies in being one of the first widely adopted, openly documented, text-based formats for formatted documents, predating the XML-based office formats by roughly two decades. It demonstrated that rich formatting could be carried in a human-readable control-word syntax that any developer could implement, a lineage that ultimately leads to the XML packaging of Office Open XML and OpenDocument. Although those newer formats have largely supplanted it for primary storage, RTF remains supported as a near-universal import and export option and lives on inside system text controls and the clipboard.