Lines starting with zero or more whitespace characters followed by one # and a whitespace are treated as comments and, as such, are not exported.

Likewise, regions surrounded by #+BEGIN_COMMENT … #+END_COMMENT are not exported.

Keywords are structured according to the following pattern:

#+KEY: VALUE

KEY A string consisting of any non-whitespace characters, other than call (which would forms a babel call element). VALUE A string consisting of any characters but a newline.

Some notable keywords of relevance to the export process:

• OPTIONS
• BIND
• MACRO

Properties are key–value pairs. When they are associated with a single entry or with a tree they need to be inserted into a special drawer (see Drawers) with the name PROPERTIES, which has to be located right below a headline, and its planning line (see Deadlines and Scheduling) when applicable. Each property is specified on a single line, with the key—surrounded by colons—first, and the value after it. Keys are case-insensitive. Here is an example:

* CD collection
** Classic
*** Goldberg Variations
    :PROPERTIES:
    :Title:     Goldberg Variations
    :Composer:  J.S. Bach
    :END:

The general link format, … looks like this:

[[LINK][DESCRIPTION]]

or alternatively

[[LINK]]

Additionally, several ways of defining internal links²⁵²⁵I.e., within a file such as foo.org. are supported:

• [[#my-custom-id]] will point to a node with CUSTOM_ID property set to my-custom-id.
• [[*My section]] will point to a headline with the name My section.
• [[my target]] will first try and look for (and match to) an occurrence of <<my target>> in the file; if none found, it’ll try and match to an element with the NAME set to my target.

Paragraphs are separated by at least one empty line. If you need to enforce a line break within a paragraph, use \\ at the end of a line.

In addition, there also ways to represent blocks of text that preserve line-breaks²⁶²⁶Verse block., quote a passage from another document²⁷²⁷Quote block., and centering some text.²⁸²⁸Center block.

Text can also be italicized etc:

You can make words *bold*, /italic/, _underlined_, =verbatim= and ~code~, and, if you must, +strike-through+. Text in the code and verbatim string is not processed for Org specific syntax; it is exported verbatim.

[…]

Sometimes, when marked text also contains the marker character itself, the result may be unsettling… You can use zero width space²⁹²⁹Unicode 0x200B. to help Org sorting out the ambiguity.

You can also have superscripts and subscripts:

^ and _ are used to indicate super- and subscripts. To increase the readability of ASCII text, it is not necessary, but OK, to surround multi-character sub- and superscripts with curly braces.

And horizontal lines:

A line consisting of only dashes, and at least 5 of them, is exported as a horizontal line.

As well as specify custom HTML attributes:

Org files can also have special directives to the HTML export back-end. For example, by using #+ATTR_HTML lines to specify new format attributes³⁰³⁰Such as, CSS class, inlined style etc. to³¹³¹Including, but not limited to. <a> or <img> tags.

Two kinds of footnotes are supported:

• Anonymous footnotes³²³²I.e., where the definition is inlined at the point of reference.
• Named footnotes³³³³Which may be referenced multiple times.

An inline footnote is as follows:

Some text[fn::An inline footnote.] and then some more text after the footnote.

Whereas a named footnote:

… is started by a footnote marker in square brackets in column 0, no indentation allowed. It ends at the next footnote definition, headline, or after two consecutive empty lines. The footnote reference is simply the marker in square brackets, inside text. Markers always start with fn:. For example:

The Org website[fn:55] now looks a lot better than it used to.
...
[fn:55] The link is: https://orgmode.org

An image is a link to an image file that does not have a description part, for example

file:./img/cat.jpg

Equivalently, we may also have:

[[./img/cat.jpg]]

We can also add captions:

#+CAPTION: my caption
[[./img/cat.jpg]]

And customize the styling of it:

#+ATTR_HTML: :width 300px
#+CAPTION: my caption
[[./img/cat.jpg]]

Any line with | as the first non-whitespace character is considered part of a table. | is also the column separator. Moreover, a line starting with |- is a horizontal rule. It separates rows explicitly. Rows before the first horizontal rule are header lines.

The width of columns is automatically determined by the table editor. The alignment of a column is determined automatically from the fraction of number-like versus non-number fields in the column.

[…]

To set the width of a column, one field anywhere in the column may contain just the string <N> where N specifies the width as a number of characters.

[…]

If you would like to overrule the automatic alignment of number-rich columns to the right and of string-rich columns to the left, you can use <r>, <c> or <l> in a similar fashion. You may also combine alignment and field width like this: <r10>.

And Greek letters:

You can use LaTeX-like syntax to insert special symbols—named entities—like \alpha to indicate the Greek letter³⁴³⁴α, or \to to indicate an arrow³⁵³⁵→… If you need such a symbol inside a word, terminate it with a pair of curly brackets.

[…]

During export, these symbols are transformed into the native format of the exporter back-end. Strings like \alpha are exported as α in the HTML output…

One can also embed LaTeX:³⁶³⁶Which, by default, when exported to HTML will use Mathjax, but can also be configured to transcode math into images.

LaTeX fragments do not need any special marking at all. The following snippets are identified as LaTeX source code:

• Environments of any kind.³⁷³⁷When MathJax is used, only the environments recognized by MathJax are processed. When dvipng, dvisvgm, or ImageMagick suite is used to create images, any LaTeX environment is handled. The only requirement is that the \begin statement appears on a new line, preceded by only whitespace.
• Text within the usual LaTeX math delimiters. To avoid conflicts with currency specifications, single $ characters are only recognized as math delimiters if the enclosed text contains at most two line breaks, is directly attached to the $ characters with no whitespace in between, and if the closing $ is followed by whitespace, punctuation or a dash. For the other delimiters, there is no such restriction, so when in doubt, use \(...\) as inline math delimiters.

Source code can be embedded using #+BEGIN_SRC and #+END_SRC delimiters. When done so, the code will be highlighted based on the configured syntax highlighting in Emacs. A consequence of this fact is that simply by adding syntax highlighting capabilities to your editor,³⁹³⁹Assuming you use Emacs as your editor. one can get syntax highlighting in the exported output.⁴⁰⁴⁰Using the htmlize Emacs package for HTML output format. For monospace content, the #+BEGIN_EXAMPLE and #+END_EXAMPLE delimiters can be used instead. Additionally,

Both in example and in src snippets, you can add a -n switch to the end of the #+BEGIN line, to get the lines of the example numbered. The -n takes an optional numeric argument specifying the starting line number of the block. If you use a +n switch, the numbering from the previous numbered snippet is continued in the current one. The +n switch can also take a numeric argument. This adds the value of the argument to the last line of the previous block to determine the starting line number.

There’s also the ability to link to specific lines in the source code as well as the ability to highlight the specific line in the code example when hovering over a reference in the generated HTML.