File Format

%docu mark

Note: this section is mostly useful if you're writing a mark conversion method. For marks that are already supported and you can use directly, see further down this page.

The %docs app supports any mark, as long as it has a conversion method to its %docu mark. The %docu mark is not expected to be used directly to write documentation, its purpose is to be a mark conversion target.

The %docu mark expects a $manx.

A $manx is how an XML node structure is represented in hoon. See Section 5e of the standard library reference for details. A $manx is what ++de-xml:html and ++en-xml:html decode/encode raw XML strings from/to.

The %docu mark will technically accept any $manx, but the %docs agent itself makes some changes and imposes some additional rules:

  • The root element must be a <div>.
  • <h1>, <h2>, and <h3> elements that are direct children of the root <div> will be used to make the table of contents. Other header levels will not be included in the table of contents, but they can still be used. <h1>, through <h3> can also be used at deeper levels, but they also won't be included in the table of contents.
  • Only these tags are allowed: <a>, <address>, <b>, <br>, <blockquote>, <code>, <del>, <div>, <em>, <h1>, <h2>, <h3>, <h4>, <h5>, <h6>, <hr>, <i>, <img>, <ins>, <li>, <ol>, <p>, <pre>, <q>, <small>, <span>, <strong>, <sub>, <sup>, <time>, <ul>, <var>.
  • Inside the <h1>, <h2>, and <h3> headers that are direct children of the root <div> (and will therefore be used in the table of contents), only a subset of the tags listed above are allowed: <b>, <code>, <del>, <em>, <i>, <ins>, <q>, <small>, <span>, <strong>, <sub>, <sup>, <time>, <var>.
  • All attributes will be stripped from all elements (you can still include them but they'll be removed), with the following exceptions:
    • The src and alt attributes in an <img> tag.
    • The href attribute in an <a> tag.
    • A class attribute in a <pre> tag beginning with language- (e.g. class="language-hoon"). This is not currently used for anything but will be used for syntax highlighting in the future.

Note: table elements are not currently supported but will likely be added in a future release.

Included marks

The following marks are supported by the %docs app and you can use them to write docs right away.


Udon is a markdown-like language native to hoon, with a parser built into the hoon compiler. Here is its syntax in brief:

  • The first line of the .udon document must be a single rune: ;>. This tells the compiler to interpret everything following as udon.
  • Paragraphs: Content on a single line will be made into a paragraph. Paragraphs may be hard-wrapped, so consecutive lines of text will become a single paragraph. The paragraph will be ended by an empty line or other block element.
  • Headers: lines beginning with 1-6 #s followed by a single space and then some content (e.g. ## foo) will be made into headers. The number of #s dictates the header level.
  • Italics: content wrapped in single _s (e.g. _foo_) will be made italic.
  • Bold: content wrapped in single *s (e.g. *foo*) will be made bold.
  • Unordered lists: lines beginning with - followed by a space will be made into items in a list. List lines can be hard-wrapped, with two spaces beginning each subsequent line to be included in the list. Lists can be nested by indenting the -s a further two spaces for each level of nesting.
  • Ordered lists: lines beginning with + followed by a space will be made into ordered lists, and numbered in the order they appear. These have the same wrapping and nesting logic as unordered lists.
  • Links: this is standard markdown syntax: square bracks containing the display content and then parentheses containing the URL, e.g. [foo]( The URL may also be a relative link or an anchor link.
  • Images: this is also standard markdown; a link with an exclamation mark at the beginning, e.g. ![foo]( The square brackets contain the alt-text and the the parentheses contain the image URL.
  • Inline code: text wrapped in single backticks will be rendered verbatim in a monospace font.
  • Fenced codeblocks: Triple-backticks on their own line begin and end a codeblock. All lines in between will be rendered verbatim in a monospace font. Note that udon does not support a language specification after the opening backticks like markdown does.
  • Horizontal rules: Three or more hyphens (---) will create a horizontal rule.
  • Block quotes: a line beginning with > creates a block quote. This may be hard-wrapped, as long as the next line is indented two spaces. Block quotes may contain anything, including other blockquotes.
  • Line breaks: A line ending in a single backslash will have a line break inserted at the end, so it will not flow together with the subsequent line as is usually the case.
  • Escape characters: You may prefix Udon syntax with a backslash to have it treated as the literal text.
  • Hoon constants: Udon will automatically render any values with atom aura syntax as inline code. It'll also render arms like ++foo:bar, +$baz, and +*foo:bar:baz, as inline code.
  • Sail: this is hoon's native XML syntax. Udon will parse it, execute it, and include the +$manxes produced in the resulting document. This means you can embed arbitrary hoon in the document. There is little formal sail documentation, but you can refer to the ; (mic) rune reference for most of its runes and some rudimentary examples.

Note: Udon is quite strict on its syntax, and may fail to parse if it's incorrect.


The %docs app supports plain .txt files. The file will be rendered as a preformatted codeblock with wrapping.


Ordinary HTML files may be used, but note the tag and structural restrictions described in the %docu mark description above.


Gemtext is an ultra-minimal markup format developed for the Gemini project, an internet protocol for serving light-weight hypertext, inspired by Gopher. Its file extension is .gmi.

Gemtext interprets things on a line-by-line basis, and does not support different types on a single line. Every line is a separate element, with the exception of fenced codeblocks which may span multiple lines. In brief, here is the syntax:

  • Paragraphs: Plain text on a single line constitutes a paragraph. Note hard-wrapping is not supported.
  • Links: lines beginning with => followed by a space create a link. After the space, the target URL is given. After the URL, there may optionally be a space and then some display text for the link. If no displace text is given, the URL itself will be displayed.
  • Codeblocks: triple-backticks at the beginning of a line begin and end a codeblock. All text in between will be rendered verbatim in a monospace font. The opening backticks may optionally be followed by some text, which will be used as the language tag.
  • Headings: 1-3 #s followed by text create a heading. The number of #s determine the heading level.
  • Lists: lines beginning with * followed by a space and then text will create a list item.
  • Quotes: lines beginning with > followed by a space creates a blockquote.