Plain text

In, plain text is a loose term for data (e.g. file contents) that represent only s of readable material but not its graphical representation nor other objects (floating-point numbers, images, etc.). It may also include a limited number of characters that control simple arrangement of text, such as spaces, line breaks, or tabulation characters (although tab characters can "mean" many different things, so are hardly "plain"). Plain text is different from, where style information is included; from structured text, where structural parts of the document such as paragraphs, sections, and the like are identified; and from binary files in which some portions must be interpreted as binary objects (encoded integers, real numbers, images, etc.).

Basic definition
The term is sometimes used quite loosely, to mean files that contain only "readable" content (or just files with nothing that the speaker doesn't prefer). For example, that could exclude any indication of fonts or layout (such as markup, markdown, or even tabs); characters such as curly quotes, non-breaking spaces, soft hyphens, em dashes, and/or ligatures; or other things.

In principle, plain text can be in any, but occasionally the term is taken to imply ASCII. As Unicode-based encodings such as and  become more common, that usage may be shrinking.

Plain text is also sometimes used only to exclude "binary" files: those in which at least some parts of the file cannot be correctly interpreted via the character encoding in effect. For example, a file or string consisting of "hello" (in whatever encoding), following by 4 bytes that express a binary integer that is not just a character, is a binary file, not plain text by even the loosest common usages. Put another way, translating a plain text file to a character encoding that uses entirely different number to represent s, does not change the meaning (so long as you know what encoding is in use), but for binary files such a conversion does change the meaning of at least some parts of the file.

Plain text and Mac OS
In classic Mac OS, plain text was supported by Apple Computer's first basic text editor, TeachText. The filetype was  and could be made read-only by changing it to. SimpleText added some formatting capability by storing additional data in the resource fork, though only the basic text was readable by PCs.

In Mac OS X and macOS, SimpleText was replaced by TextEdit, which added support for Unicode and supported plain text as  files. Formatted text was saved in  format, and formatted text with attachments (such as embedded images) was saved in   format.