RTF, the Rich Text Format, was created by Microsoft's Word team and first published in 1987. Its purpose was exchange: in an era when every word processor had its own closed file format, RTF gave them a common one, so a document written in one program could be opened in another with its fonts, bold and italics, paragraphs and tables intact.
Plain text with instructions
Open an RTF file in a plain text editor and you can read it. The formatting is written into the text as control words, which start with a backslash, and curly braces group the parts they apply to. A minimal document looks like this:
{\rtf1\ansi{\fonttbl\f0\fswiss Helvetica;}\f0\pard This is {\b bold} text.\par}
Here \rtf1 marks the file as RTF version 1, \fonttbl lists the fonts, \b switches bold on inside its group, and \par ends a paragraph. RTF files are written in 7-bit ASCII, so characters outside the basic Latin alphabet are escaped: an é is stored as \'e9 or, for full Unicode, as \u233 followed by a fallback character.
Why it is still around
- It opens almost everywhere. Word, LibreOffice, Google Docs, Apple's TextEdit and many smaller editors read RTF, including old versions of all of them.
- It is the default rich text format of macOS TextEdit, so documents written on a Mac without an office suite are often RTF files.
- It carries no macros, which made it a common choice for exchanging documents in organisations wary of Word files with embedded code.
Its limits
Microsoft stopped developing RTF after version 1.9.1 in 2008 and concentrates on DOCX. Newer features have no RTF equivalent, and each program supports a different subset of the specification, so a complex layout rarely survives a round trip unchanged. Images are stored as long runs of hexadecimal text, which makes an RTF file with pictures much larger than the same document as DOCX or ODT. For new documents that will be edited further, DOCX or ODT is usually the better choice; RTF remains handy for simple formatted text that has to open anywhere.
How the spell checker helps
The Spell Checker opens RTF files, so you can check a TextEdit document or an export from an older program without converting it first. Its text is checked for spelling, grammar and punctuation, with style suggestions in Picky mode. When you are done, download the corrected text as RTF again, or as DOCX or ODT if the document is moving on to a modern word processor. Unlike a Word or OpenDocument file, an RTF file comes back as a clean document written from the corrected text, so its fonts and styling are not carried over; for a document whose look matters, fix the mistakes the check found in the original. It is free, without an account, for up to 150,000 characters per check.