.RTF File Format – Syntax and special characters

The four kinds of element

The whole file is one group that starts {\rtf1. A standard RTF file can be written with 7-bit ASCII only; Word for Windows and for the Macintosh also write 8-bit characters, so readers should accept them. There is no maximum line length. To use a backslash or brace as text, write \\, \{ or \}.

Control words

A control word is a backslash, a sequence of lower-case letters a to z, and a delimiter. It is at most 32 characters long, and RTF is case sensitive. The delimiter is one of:

Parameters are generally in the range −32,767 to 32,767; Word tends to keep them within −31,680 to 31,680, but allows a full 32-bit range for a few words (\bin, \revdttm and some picture properties). A reader must accept any string of digits. A parameter that is needed but missing takes the word’s default, or 0 when the word gives none.

Words that switch a property on and off, such as \b for bold, turn it on with no parameter or a non-zero one and off with 0: \b starts bold and \b0 ends it. On these pages such words are marked “toggle”.

Word 97 and 2000 broke the lower-case rule for a few table words. Writers should use lower case, but readers should accept these exceptions: \clFitText, \clftsWidthN, \clNoWrap, \clwWidthN, \tdfrmtxtBottomN, \tdfrmtxtLeftN, \tdfrmtxtRightN, \tdfrmtxtTopN, \trftsWidthAN, \trftsWidthBN, \trftsWidthN, \trwWidthAN, \trwWidthBN, \trwWidthN and \sectspecifygenN.

Lengths are in twips, twentieths of a point (1,440 to the inch), unless a word says otherwise. Font sizes are in half-points.

Groups and destinations

A group is text and control information in braces. Formatting set inside a group applies only inside it; at the closing brace the reader goes back to the state it had at the opening brace. Text in a group otherwise inherits the formatting before it, but Microsoft’s readers do not let footnote, annotation, header and footer groups inherit, so writers should reset them with \sectd, \pard and \plain.

A destination is a control word that starts a block of text that belongs somewhere else, or is not shown at all: \footnote, \header, \pict, \info, \fonttbl, \stylesheet, \colortbl and many more. A destination must come straight after an opening brace, and the group holds nothing else. Page breaks cannot occur in destination text.

The control symbol \* before a destination word means “skip this whole group if you do not know the destination”. Every destination added after the March 1987 specification is written with it, for example {\*\bkmkstart Name}. A destination that should still be shown by a reader that does not know it is written without \*. Every RTF reader must handle \*.

The groups that make up the header (font, file, colour, style, list and revision tables) and the document formatting properties must all come before the first character of text.

How a reader works

The specification describes a reader that takes the file one character at a time:

• {: push the current state (destination and character, paragraph, section and table properties) on a stack.
• }: pop the state back off the stack.
• \: read the control word or symbol and its parameter, look it up and do what it says. An unknown control word is ignored; an unknown destination after \* is skipped up to its closing brace.
• Anything else: write it as text to the current destination. Carriage returns and line feeds are ignored, unless they follow a backslash.

A known control word does one of four things:

Formal syntax notation

The specification describes the grammar of each part in a form of Backus-Naur notation, which these pages repeat where it helps:

The top level is <File> = '{' <header> <document> '}'.

Characters outside ASCII and binary data

Example: the text LabΓValue is written Lab\u915Gvalue when \uc1 is in force: Γ is U+0393, 915 in decimal, and G is the one-byte fallback.

Special characters

These control words and symbols stand for a character or a break. A reader that does not know one ignores it and reads what follows as text.

A carriage return (13) or line feed (10) after a backslash means \par; on its own it is ignored, so writers can break lines anywhere, and the specification suggests a line break at least every 255 characters. A tab character (9) should be read as \tab, but writers should always write the control word.

The quotation marks, dashes and bullet have these byte values in the two character sets that Word uses:

Example

A complete document whose only text is “This is plain text.”, after the example in the specification (shortened colour table; lines broken only where a line break means nothing):

{\rtf1\ansi\deff0
{\fonttbl{\f0\froman Tms Rmn;}{\f1\fdecor Symbol;}{\f2\fswiss Helv;}}
{\colortbl;\red0\green0\blue0;\red0\green0\blue255;}
{\stylesheet{\fs20 \snext0 Normal;}}
{\info{\author John Doe}{\creatim\yr1990\mo7\dy30\hr10\min48}
{\version1}{\edmins0}{\nofpages1}{\nofwords0}{\nofchars0}{\vern8351}}
\widowctrl\ftnbj \sectd\linex0\endnhere \pard\plain \fs20 This is plain text.\par
}

Read in order: the version and character set (\rtf1, \ansi), the default font (\deff0), the font table, colour table and style sheet, the information group, document properties (\widowctrl, \ftnbj), section properties (\sectd\linex0\endnhere), the paragraph and character resets (\pard\plain), a font size of 10 points (\fs20), the text and the paragraph mark. The space after \fs20 ends the control word and is not part of the text.