blob: ff44e4afad66037e152ffd213b27fb474f2a56b9 [file] [log] [blame]
---
title: CommonMark Spec
author: John MacFarlane
version: 0.22
date: 2015-08-23
license: '[CC-BY-SA 4.0](http://creativecommons.org/licenses/by-sa/4.0/)'
...
# Introduction
## What is Markdown?
Markdown is a plain text format for writing structured documents,
based on conventions used for indicating formatting in email and
usenet posts. It was developed in 2004 by John Gruber, who wrote
the first Markdown-to-HTML converter in perl, and it soon became
widely used in websites. By 2014 there were dozens of
implementations in many languages. Some of them extended basic
Markdown syntax with conventions for footnotes, definition lists,
tables, and other constructs, and some allowed output not just in
HTML but in LaTeX and many other formats.
## Why is a spec needed?
John Gruber's [canonical description of Markdown's
syntax](http://daringfireball.net/projects/markdown/syntax)
does not specify the syntax unambiguously. Here are some examples of
questions it does not answer:
1. How much indentation is needed for a sublist? The spec says that
continuation paragraphs need to be indented four spaces, but is
not fully explicit about sublists. It is natural to think that
they, too, must be indented four spaces, but `Markdown.pl` does
not require that. This is hardly a "corner case," and divergences
between implementations on this issue often lead to surprises for
users in real documents. (See [this comment by John
Gruber](http://article.gmane.org/gmane.text.markdown.general/1997).)
2. Is a blank line needed before a block quote or header?
Most implementations do not require the blank line. However,
this can lead to unexpected results in hard-wrapped text, and
also to ambiguities in parsing (note that some implementations
put the header inside the blockquote, while others do not).
(John Gruber has also spoken [in favor of requiring the blank
lines](http://article.gmane.org/gmane.text.markdown.general/2146).)
3. Is a blank line needed before an indented code block?
(`Markdown.pl` requires it, but this is not mentioned in the
documentation, and some implementations do not require it.)
``` markdown
paragraph
code?
```
4. What is the exact rule for determining when list items get
wrapped in `<p>` tags? Can a list be partially "loose" and partially
"tight"? What should we do with a list like this?
``` markdown
1. one
2. two
3. three
```
Or this?
``` markdown
1. one
- a
- b
2. two
```
(There are some relevant comments by John Gruber
[here](http://article.gmane.org/gmane.text.markdown.general/2554).)
5. Can list markers be indented? Can ordered list markers be right-aligned?
``` markdown
8. item 1
9. item 2
10. item 2a
```
6. Is this one list with a horizontal rule in its second item,
or two lists separated by a horizontal rule?
``` markdown
* a
* * * * *
* b
```
7. When list markers change from numbers to bullets, do we have
two lists or one? (The Markdown syntax description suggests two,
but the perl scripts and many other implementations produce one.)
``` markdown
1. fee
2. fie
- foe
- fum
```
8. What are the precedence rules for the markers of inline structure?
For example, is the following a valid link, or does the code span
take precedence ?
``` markdown
[a backtick (`)](/url) and [another backtick (`)](/url).
```
9. What are the precedence rules for markers of emphasis and strong
emphasis? For example, how should the following be parsed?
``` markdown
*foo *bar* baz*
```
10. What are the precedence rules between block-level and inline-level
structure? For example, how should the following be parsed?
``` markdown
- `a long code span can contain a hyphen like this
- and it can screw things up`
```
11. Can list items include section headers? (`Markdown.pl` does not
allow this, but does allow blockquotes to include headers.)
``` markdown
- # Heading
```
12. Can list items be empty?
``` markdown
* a
*
* b
```
13. Can link references be defined inside block quotes or list items?
``` markdown
> Blockquote [foo].
>
> [foo]: /url
```
14. If there are multiple definitions for the same reference, which takes
precedence?
``` markdown
[foo]: /url1
[foo]: /url2
[foo][]
```
In the absence of a spec, early implementers consulted `Markdown.pl`
to resolve these ambiguities. But `Markdown.pl` was quite buggy, and
gave manifestly bad results in many cases, so it was not a
satisfactory replacement for a spec.
Because there is no unambiguous spec, implementations have diverged
considerably. As a result, users are often surprised to find that
a document that renders one way on one system (say, a github wiki)
renders differently on another (say, converting to docbook using
pandoc). To make matters worse, because nothing in Markdown counts
as a "syntax error," the divergence often isn't discovered right away.
## About this document
This document attempts to specify Markdown syntax unambiguously.
It contains many examples with side-by-side Markdown and
HTML. These are intended to double as conformance tests. An
accompanying script `spec_tests.py` can be used to run the tests
against any Markdown program:
python test/spec_tests.py --spec spec.txt --program PROGRAM
Since this document describes how Markdown is to be parsed into
an abstract syntax tree, it would have made sense to use an abstract
representation of the syntax tree instead of HTML. But HTML is capable
of representing the structural distinctions we need to make, and the
choice of HTML for the tests makes it possible to run the tests against
an implementation without writing an abstract syntax tree renderer.
This document is generated from a text file, `spec.txt`, written
in Markdown with a small extension for the side-by-side tests.
The script `tools/makespec.py` can be used to convert `spec.txt` into
HTML or CommonMark (which can then be converted into other formats).
In the examples, the `→` character is used to represent tabs.
# Preliminaries
## Characters and lines
Any sequence of [character]s is a valid CommonMark
document.
A [character](@character) is a Unicode code point. Although some
code points (for example, combining accents) do not correspond to
characters in an intuitive sense, all code points count as characters
for purposes of this spec.
This spec does not specify an encoding; it thinks of lines as composed
of [character]s rather than bytes. A conforming parser may be limited
to a certain encoding.
A [line](@line) is a sequence of zero or more [character]s
other than newline (`U+000A`) or carriage return (`U+000D`),
followed by a [line ending] or by the end of file.
A [line ending](@line-ending) is a newline (`U+000A`), a carriage return
(`U+000D`) not followed by a newline, or a carriage return and a
following newline.
A line containing no characters, or a line containing only spaces
(`U+0020`) or tabs (`U+0009`), is called a [blank line](@blank-line).
The following definitions of character classes will be used in this spec:
A [whitespace character](@whitespace-character) is a space
(`U+0020`), tab (`U+0009`), newline (`U+000A`), line tabulation (`U+000B`),
form feed (`U+000C`), or carriage return (`U+000D`).
[Whitespace](@whitespace) is a sequence of one or more [whitespace
character]s.
A [Unicode whitespace character](@unicode-whitespace-character) is
any code point in the Unicode `Zs` class, or a tab (`U+0009`),
carriage return (`U+000D`), newline (`U+000A`), or form feed
(`U+000C`).
[Unicode whitespace](@unicode-whitespace) is a sequence of one
or more [Unicode whitespace character]s.
A [space](@space) is `U+0020`.
A [non-whitespace character](@non-whitespace-character) is any character
that is not a [whitespace character].
An [ASCII punctuation character](@ascii-punctuation-character)
is `!`, `"`, `#`, `$`, `%`, `&`, `'`, `(`, `)`,
`*`, `+`, `,`, `-`, `.`, `/`, `:`, `;`, `<`, `=`, `>`, `?`, `@`,
`[`, `\`, `]`, `^`, `_`, `` ` ``, `{`, `|`, `}`, or `~`.
A [punctuation character](@punctuation-character) is an [ASCII
punctuation character] or anything in
the Unicode classes `Pc`, `Pd`, `Pe`, `Pf`, `Pi`, `Po`, or `Ps`.
## Tabs
Tabs in lines are not expanded to [spaces][space]. However,
in contexts where indentation is significant for the
document's structure, tabs behave as if they were replaced
by spaces with a tab stop of 4 characters.
.
→foo→baz→→bim
.
<pre><code>foo→baz→→bim
</code></pre>
.
.
→foo→baz→→bim
.
<pre><code>foo→baz→→bim
</code></pre>
.
.
a→a
ὐ→a
.
<pre><code>a→a
ὐ→a
</code></pre>
.
.
- foo
→bar
.
<ul>
<li>
<p>foo</p>
<p>bar</p>
</li>
</ul>
.
.
>→foo→bar
.
<blockquote>
<p>foo→bar</p>
</blockquote>
.
.
foo
→bar
.
<pre><code>foo
bar
</code></pre>
.
## Insecure characters
For security reasons, the Unicode character `U+0000` must be replaced
with the replacement character (`U+FFFD`).
# Blocks and inlines
We can think of a document as a sequence of
[blocks](@block)---structural elements like paragraphs, block
quotations, lists, headers, rules, and code blocks. Some blocks (like
block quotes and list items) contain other blocks; others (like
headers and paragraphs) contain [inline](@inline) content---text,
links, emphasized text, images, code, and so on.
## Precedence
Indicators of block structure always take precedence over indicators
of inline structure. So, for example, the following is a list with
two items, not a list with one item containing a code span:
.
- `one
- two`
.
<ul>
<li>`one</li>
<li>two`</li>
</ul>
.
This means that parsing can proceed in two steps: first, the block
structure of the document can be discerned; second, text lines inside
paragraphs, headers, and other block constructs can be parsed for inline
structure. The second step requires information about link reference
definitions that will be available only at the end of the first
step. Note that the first step requires processing lines in sequence,
but the second can be parallelized, since the inline parsing of
one block element does not affect the inline parsing of any other.
## Container blocks and leaf blocks
We can divide blocks into two types:
[container block](@container-block)s,
which can contain other blocks, and [leaf block](@leaf-block)s,
which cannot.
# Leaf blocks
This section describes the different kinds of leaf block that make up a
Markdown document.
## Horizontal rules
A line consisting of 0-3 spaces of indentation, followed by a sequence
of three or more matching `-`, `_`, or `*` characters, each followed
optionally by any number of spaces, forms a
[horizontal rule](@horizontal-rule).
.
***
---
___
.
<hr />
<hr />
<hr />
.
Wrong characters:
.
+++
.
<p>+++</p>
.
.
===
.
<p>===</p>
.
Not enough characters:
.
--
**
__
.
<p>--
**
__</p>
.
One to three spaces indent are allowed:
.
***
***
***
.
<hr />
<hr />
<hr />
.
Four spaces is too many:
.
***
.
<pre><code>***
</code></pre>
.
.
Foo
***
.
<p>Foo
***</p>
.
More than three characters may be used:
.
_____________________________________
.
<hr />
.
Spaces are allowed between the characters:
.
- - -
.
<hr />
.
.
** * ** * ** * **
.
<hr />
.
.
- - - -
.
<hr />
.
Spaces are allowed at the end:
.
- - - -
.
<hr />
.
However, no other characters may occur in the line:
.
_ _ _ _ a
a------
---a---
.
<p>_ _ _ _ a</p>
<p>a------</p>
<p>---a---</p>
.
It is required that all of the [non-whitespace character]s be the same.
So, this is not a horizontal rule:
.
*-*
.
<p><em>-</em></p>
.
Horizontal rules do not need blank lines before or after:
.
- foo
***
- bar
.
<ul>
<li>foo</li>
</ul>
<hr />
<ul>
<li>bar</li>
</ul>
.
Horizontal rules can interrupt a paragraph:
.
Foo
***
bar
.
<p>Foo</p>
<hr />
<p>bar</p>
.
If a line of dashes that meets the above conditions for being a
horizontal rule could also be interpreted as the underline of a [setext
header], the interpretation as a
[setext header] takes precedence. Thus, for example,
this is a setext header, not a paragraph followed by a horizontal rule:
.
Foo
---
bar
.
<h2>Foo</h2>
<p>bar</p>
.
When both a horizontal rule and a list item are possible
interpretations of a line, the horizontal rule takes precedence:
.
* Foo
* * *
* Bar
.
<ul>
<li>Foo</li>
</ul>
<hr />
<ul>
<li>Bar</li>
</ul>
.
If you want a horizontal rule in a list item, use a different bullet:
.
- Foo
- * * *
.
<ul>
<li>Foo</li>
<li>
<hr />
</li>
</ul>
.
## ATX headers
An [ATX header](@atx-header)
consists of a string of characters, parsed as inline content, between an
opening sequence of 1--6 unescaped `#` characters and an optional
closing sequence of any number of unescaped `#` characters.
The opening sequence of `#` characters cannot be followed directly by a
[non-whitespace character]. The optional closing sequence of `#`s must be
preceded by a [space] and may be followed by spaces only. The opening
`#` character may be indented 0-3 spaces. The raw contents of the
header are stripped of leading and trailing spaces before being parsed
as inline content. The header level is equal to the number of `#`
characters in the opening sequence.
Simple headers:
.
# foo
## foo
### foo
#### foo
##### foo
###### foo
.
<h1>foo</h1>
<h2>foo</h2>
<h3>foo</h3>
<h4>foo</h4>
<h5>foo</h5>
<h6>foo</h6>
.
More than six `#` characters is not a header:
.
####### foo
.
<p>####### foo</p>
.
At least one space is required between the `#` characters and the
header's contents, unless the header is empty. Note that many
implementations currently do not require the space. However, the
space was required by the
[original ATX implementation](http://www.aaronsw.com/2002/atx/atx.py),
and it helps prevent things like the following from being parsed as
headers:
.
#5 bolt
#foobar
.
<p>#5 bolt</p>
<p>#foobar</p>
.
This is not a header, because the first `#` is escaped:
.
\## foo
.
<p>## foo</p>
.
Contents are parsed as inlines:
.
# foo *bar* \*baz\*
.
<h1>foo <em>bar</em> *baz*</h1>
.
Leading and trailing blanks are ignored in parsing inline content:
.
# foo
.
<h1>foo</h1>
.
One to three spaces indentation are allowed:
.
### foo
## foo
# foo
.
<h3>foo</h3>
<h2>foo</h2>
<h1>foo</h1>
.
Four spaces are too much:
.
# foo
.
<pre><code># foo
</code></pre>
.
.
foo
# bar
.
<p>foo
# bar</p>
.
A closing sequence of `#` characters is optional:
.
## foo ##
### bar ###
.
<h2>foo</h2>
<h3>bar</h3>
.
It need not be the same length as the opening sequence:
.
# foo ##################################
##### foo ##
.
<h1>foo</h1>
<h5>foo</h5>
.
Spaces are allowed after the closing sequence:
.
### foo ###
.
<h3>foo</h3>
.
A sequence of `#` characters with anything but [space]s following it
is not a closing sequence, but counts as part of the contents of the
header:
.
### foo ### b
.
<h3>foo ### b</h3>
.
The closing sequence must be preceded by a space:
.
# foo#
.
<h1>foo#</h1>
.
Backslash-escaped `#` characters do not count as part
of the closing sequence:
.
### foo \###
## foo #\##
# foo \#
.
<h3>foo ###</h3>
<h2>foo ###</h2>
<h1>foo #</h1>
.
ATX headers need not be separated from surrounding content by blank
lines, and they can interrupt paragraphs:
.
****
## foo
****
.
<hr />
<h2>foo</h2>
<hr />
.
.
Foo bar
# baz
Bar foo
.
<p>Foo bar</p>
<h1>baz</h1>
<p>Bar foo</p>
.
ATX headers can be empty:
.
##
#
### ###
.
<h2></h2>
<h1></h1>
<h3></h3>
.
## Setext headers
A [setext header](@setext-header)
consists of a line of text, containing at least one [non-whitespace character],
with no more than 3 spaces indentation, followed by a [setext header
underline]. The line of text must be
one that, were it not followed by the setext header underline,
would be interpreted as part of a paragraph: it cannot be
interpretable as a [code fence], [ATX header][ATX headers],
[block quote][block quotes], [horizontal rule][horizontal rules],
[list item][list items], or [HTML block][HTML blocks].
A [setext header underline](@setext-header-underline) is a sequence of
`=` characters or a sequence of `-` characters, with no more than 3
spaces indentation and any number of trailing spaces. If a line
containing a single `-` can be interpreted as an
empty [list items], it should be interpreted this way
and not as a [setext header underline].
The header is a level 1 header if `=` characters are used in the
[setext header underline], and a level 2
header if `-` characters are used. The contents of the header are the
result of parsing the first line as Markdown inline content.
In general, a setext header need not be preceded or followed by a
blank line. However, it cannot interrupt a paragraph, so when a
setext header comes after a paragraph, a blank line is needed between
them.
Simple examples:
.
Foo *bar*
=========
Foo *bar*
---------
.
<h1>Foo <em>bar</em></h1>
<h2>Foo <em>bar</em></h2>
.
The underlining can be any length:
.
Foo
-------------------------
Foo
=
.
<h2>Foo</h2>
<h1>Foo</h1>
.
The header content can be indented up to three spaces, and need
not line up with the underlining:
.
Foo
---
Foo
-----
Foo
===
.
<h2>Foo</h2>
<h2>Foo</h2>
<h1>Foo</h1>
.
Four spaces indent is too much:
.
Foo
---
Foo
---
.
<pre><code>Foo
---
Foo
</code></pre>
<hr />
.
The setext header underline can be indented up to three spaces, and
may have trailing spaces:
.
Foo
----
.
<h2>Foo</h2>
.
Four spaces is too much:
.
Foo
---
.
<p>Foo
---</p>
.
The setext header underline cannot contain internal spaces:
.
Foo
= =
Foo
--- -
.
<p>Foo
= =</p>
<p>Foo</p>
<hr />
.
Trailing spaces in the content line do not cause a line break:
.
Foo
-----
.
<h2>Foo</h2>
.
Nor does a backslash at the end:
.
Foo\
----
.
<h2>Foo\</h2>
.
Since indicators of block structure take precedence over
indicators of inline structure, the following are setext headers:
.
`Foo
----
`
<a title="a lot
---
of dashes"/>
.
<h2>`Foo</h2>
<p>`</p>
<h2>&lt;a title=&quot;a lot</h2>
<p>of dashes&quot;/&gt;</p>
.
The setext header underline cannot be a [lazy continuation
line] in a list item or block quote:
.
> Foo
---
.
<blockquote>
<p>Foo</p>
</blockquote>
<hr />
.
.
- Foo
---
.
<ul>
<li>Foo</li>
</ul>
<hr />
.
A setext header cannot interrupt a paragraph:
.
Foo
Bar
---
Foo
Bar
===
.
<p>Foo
Bar</p>
<hr />
<p>Foo
Bar
===</p>
.
But in general a blank line is not required before or after:
.
---
Foo
---
Bar
---
Baz
.
<hr />
<h2>Foo</h2>
<h2>Bar</h2>
<p>Baz</p>
.
Setext headers cannot be empty:
.
====
.
<p>====</p>
.
Setext header text lines must not be interpretable as block
constructs other than paragraphs. So, the line of dashes
in these examples gets interpreted as a horizontal rule:
.
---
---
.
<hr />
<hr />
.
.
- foo
-----
.
<ul>
<li>foo</li>
</ul>
<hr />
.
.
foo
---
.
<pre><code>foo
</code></pre>
<hr />
.
.
> foo
-----
.
<blockquote>
<p>foo</p>
</blockquote>
<hr />
.
If you want a header with `> foo` as its literal text, you can
use backslash escapes:
.
\> foo
------
.
<h2>&gt; foo</h2>
.
## Indented code blocks
An [indented code block](@indented-code-block) is composed of one or more
[indented chunk]s separated by blank lines.
An [indented chunk](@indented-chunk) is a sequence of non-blank lines,
each indented four or more spaces. The contents of the code block are
the literal contents of the lines, including trailing
[line ending]s, minus four spaces of indentation.
An indented code block has no [info string].
An indented code block cannot interrupt a paragraph, so there must be
a blank line between a paragraph and a following indented code block.
(A blank line is not needed, however, between a code block and a following
paragraph.)
.
a simple
indented code block
.
<pre><code>a simple
indented code block
</code></pre>
.
If there is any ambiguity between an interpretation of indentation
as a code block and as indicating that material belongs to a [list
item][list items], the list item interpretation takes precedence:
.
- foo
bar
.
<ul>
<li>
<p>foo</p>
<p>bar</p>
</li>
</ul>
.
.
1. foo
- bar
.
<ol>
<li>
<p>foo</p>
<ul>
<li>bar</li>
</ul>
</li>
</ol>
.
The contents of a code block are literal text, and do not get parsed
as Markdown:
.
<a/>
*hi*
- one
.
<pre><code>&lt;a/&gt;
*hi*
- one
</code></pre>
.
Here we have three chunks separated by blank lines:
.
chunk1
chunk2
chunk3
.
<pre><code>chunk1
chunk2
chunk3
</code></pre>
.
Any initial spaces beyond four will be included in the content, even
in interior blank lines:
.
chunk1
chunk2
.
<pre><code>chunk1
chunk2
</code></pre>
.
An indented code block cannot interrupt a paragraph. (This
allows hanging indents and the like.)
.
Foo
bar
.
<p>Foo
bar</p>
.
However, any non-blank line with fewer than four leading spaces ends
the code block immediately. So a paragraph may occur immediately
after indented code:
.
foo
bar
.
<pre><code>foo
</code></pre>
<p>bar</p>
.
And indented code can occur immediately before and after other kinds of
blocks:
.
# Header
foo
Header
------
foo
----
.
<h1>Header</h1>
<pre><code>foo
</code></pre>
<h2>Header</h2>
<pre><code>foo
</code></pre>
<hr />
.
The first line can be indented more than four spaces:
.
foo
bar
.
<pre><code> foo
bar
</code></pre>
.
Blank lines preceding or following an indented code block
are not included in it:
.
foo
.
<pre><code>foo
</code></pre>
.
Trailing spaces are included in the code block's content:
.
foo
.
<pre><code>foo
</code></pre>
.
## Fenced code blocks
A [code fence](@code-fence) is a sequence
of at least three consecutive backtick characters (`` ` ``) or
tildes (`~`). (Tildes and backticks cannot be mixed.)
A [fenced code block](@fenced-code-block)
begins with a code fence, indented no more than three spaces.
The line with the opening code fence may optionally contain some text
following the code fence; this is trimmed of leading and trailing
spaces and called the [info string](@info-string).
The [info string] may not contain any backtick
characters. (The reason for this restriction is that otherwise
some inline code would be incorrectly interpreted as the
beginning of a fenced code block.)
The content of the code block consists of all subsequent lines, until
a closing [code fence] of the same type as the code block
began with (backticks or tildes), and with at least as many backticks
or tildes as the opening code fence. If the leading code fence is
indented N spaces, then up to N spaces of indentation are removed from
each line of the content (if present). (If a content line is not
indented, it is preserved unchanged. If it is indented less than N
spaces, all of the indentation is removed.)
The closing code fence may be indented up to three spaces, and may be
followed only by spaces, which are ignored. If the end of the
containing block (or document) is reached and no closing code fence
has been found, the code block contains all of the lines after the
opening code fence until the end of the containing block (or
document). (An alternative spec would require backtracking in the
event that a closing code fence is not found. But this makes parsing
much less efficient, and there seems to be no real down side to the
behavior described here.)
A fenced code block may interrupt a paragraph, and does not require
a blank line either before or after.
The content of a code fence is treated as literal text, not parsed
as inlines. The first word of the [info string] is typically used to
specify the language of the code sample, and rendered in the `class`
attribute of the `code` tag. However, this spec does not mandate any
particular treatment of the [info string].
Here is a simple example with backticks:
.
```
<
>
```
.
<pre><code>&lt;
&gt;
</code></pre>
.
With tildes:
.
~~~
<
>
~~~
.
<pre><code>&lt;
&gt;
</code></pre>
.
The closing code fence must use the same character as the opening
fence:
.
```
aaa
~~~
```
.
<pre><code>aaa
~~~
</code></pre>
.
.
~~~
aaa
```
~~~
.
<pre><code>aaa
```
</code></pre>
.
The closing code fence must be at least as long as the opening fence:
.
````
aaa
```
``````
.
<pre><code>aaa
```
</code></pre>
.
.
~~~~
aaa
~~~
~~~~
.
<pre><code>aaa
~~~
</code></pre>
.
Unclosed code blocks are closed by the end of the document
(or the enclosing [block quote] or [list item]):
.
```
.
<pre><code></code></pre>
.
.
`````
```
aaa
.
<pre><code>
```
aaa
</code></pre>
.
.
> ```
> aaa
bbb
.
<blockquote>
<pre><code>aaa
</code></pre>
</blockquote>
<p>bbb</p>
.
A code block can have all empty lines as its content:
.
```
```
.
<pre><code>
</code></pre>
.
A code block can be empty:
.
```
```
.
<pre><code></code></pre>
.
Fences can be indented. If the opening fence is indented,
content lines will have equivalent opening indentation removed,
if present:
.
```
aaa
aaa
```
.
<pre><code>aaa
aaa
</code></pre>
.
.
```
aaa
aaa
aaa
```
.
<pre><code>aaa
aaa
aaa
</code></pre>
.
.
```
aaa
aaa
aaa
```
.
<pre><code>aaa
aaa
aaa
</code></pre>
.
Four spaces indentation produces an indented code block:
.
```
aaa
```
.
<pre><code>```
aaa
```
</code></pre>
.
Closing fences may be indented by 0-3 spaces, and their indentation
need not match that of the opening fence:
.
```
aaa
```
.
<pre><code>aaa
</code></pre>
.
.
```
aaa
```
.
<pre><code>aaa
</code></pre>
.
This is not a closing fence, because it is indented 4 spaces:
.
```
aaa
```
.
<pre><code>aaa
```
</code></pre>
.
Code fences (opening and closing) cannot contain internal spaces:
.
``` ```
aaa
.
<p><code></code>
aaa</p>
.
.
~~~~~~
aaa
~~~ ~~
.
<pre><code>aaa
~~~ ~~
</code></pre>
.
Fenced code blocks can interrupt paragraphs, and can be followed
directly by paragraphs, without a blank line between:
.
foo
```
bar
```
baz
.
<p>foo</p>
<pre><code>bar
</code></pre>
<p>baz</p>
.
Other blocks can also occur before and after fenced code blocks
without an intervening blank line:
.
foo
---
~~~
bar
~~~
# baz
.
<h2>foo</h2>
<pre><code>bar
</code></pre>
<h1>baz</h1>
.
An [info string] can be provided after the opening code fence.
Opening and closing spaces will be stripped, and the first word, prefixed
with `language-`, is used as the value for the `class` attribute of the
`code` element within the enclosing `pre` element.
.
```ruby
def foo(x)
return 3
end
```
.
<pre><code class="language-ruby">def foo(x)
return 3
end
</code></pre>
.
.
~~~~ ruby startline=3 $%@#$
def foo(x)
return 3
end
~~~~~~~
.
<pre><code class="language-ruby">def foo(x)
return 3
end
</code></pre>
.
.
````;
````
.
<pre><code class="language-;"></code></pre>
.
[Info string]s for backtick code blocks cannot contain backticks:
.
``` aa ```
foo
.
<p><code>aa</code>
foo</p>
.
Closing code fences cannot have [info string]s:
.
```
``` aaa
```
.
<pre><code>``` aaa
</code></pre>
.
## HTML blocks
An [HTML block](@html-block) is a group of lines that is treated
as raw HTML (and will not be escaped in HTML output).
There are seven kinds of [HTML block], which can be defined
by their start and end conditions. The block begins with a line that
meets a [start condition](@start-condition) (after up to three spaces
optional indentation). It ends with the first subsequent line that
meets a matching [end condition](@end-condition), or the last line of
the document, if no line is encountered that meets the
[end condition]. If the first line meets both the [start condition]
and the [end condition], the block will contain just that line.
1. **Start condition:** line begins with the string `<script`,
`<pre`, or `<style` (case-insensitive), followed by whitespace,
the string `>`, or the end of the line.\
**End condition:** line contains an end tag
`</script>`, `</pre>`, or `</style>` (case-insensitive; it
need not match the start tag).
2. **Start condition:** line begins with the string `<!--`.\
**End condition:** line contains the string `-->`.
3. **Start condition:** line begins with the string `<?`.\
**End condition:** line contains the string `?>`.
4. **Start condition:** line begins with the string `<!`
followed by an uppercase ASCII letter.\
**End condition:** line contains the character `>`.
5. **Start condition:** line begins with the string
`<![CDATA[`.\
**End condition:** line contains the string `]]>`.
6. **Start condition:** line begins the string `<` or `</`
followed by one of the strings (case-insensitive) `address`,
`article`, `aside`, `base`, `basefont`, `blockquote`, `body`,
`caption`, `center`, `col`, `colgroup`, `dd`, `details`, `dialog`,
`dir`, `div`, `dl`, `dt`, `fieldset`, `figcaption`, `figure`,
`footer`, `form`, `frame`, `frameset`, `h1`, `head`, `header`, `hr`,
`html`, `iframe`, `legend`, `li`, `link`, `main`, `menu`, `menuitem`,
`meta`, `nav`, `noframes`, `ol`, `optgroup`, `option`, `p`, `param`,
`section`, `source`, `summary`, `table`, `tbody`, `td`,
`tfoot`, `th`, `thead`, `title`, `tr`, `track`, `ul`, followed
by [whitespace], the end of the line, the string `>`, or
the string `/>`.\
**End condition:** line is followed by a [blank line].
7. **Start condition:** line begins with a complete [open tag]
or [closing tag] (with any [tag name] other than `script`,
`style`, or `pre`) followed only by [whitespace]
or the end of the line.\
**End condition:** line is followed by a [blank line].
All types of [HTML blocks] except type 7 may interrupt
a paragraph. Blocks of type 7 may not interrupt a paragraph.
(This restriction is intended to prevent unwanted interpretation
of long tags inside a wrapped paragraph as starting HTML blocks.)
Some simple examples follow. Here are some basic HTML blocks
of type 6:
.
<table>
<tr>
<td>
hi
</td>
</tr>
</table>
okay.
.
<table>
<tr>
<td>
hi
</td>
</tr>
</table>
<p>okay.</p>
.
.
<div>
*hello*
<foo><a>
.
<div>
*hello*
<foo><a>
.
A block can also start with a closing tag:
.
</div>
*foo*
.
</div>
*foo*
.
Here we have two HTML blocks with a Markdown paragraph between them:
.
<DIV CLASS="foo">
*Markdown*
</DIV>
.
<DIV CLASS="foo">
<p><em>Markdown</em></p>
</DIV>
.
The tag on the first line can be partial, as long
as it is split where there would be whitespace:
.
<div id="foo"
class="bar">
</div>
.
<div id="foo"
class="bar">
</div>
.
.
<div id="foo" class="bar
baz">
</div>
.
<div id="foo" class="bar
baz">
</div>
.
An open tag need not be closed:
.
<div>
*foo*
*bar*
.
<div>
*foo*
<p><em>bar</em></p>
.
A partial tag need not even be completed (garbage
in, garbage out):
.
<div id="foo"
*hi*
.
<div id="foo"
*hi*
.
.
<div class
foo
.
<div class
foo
.
The initial tag doesn't even need to be a valid
tag, as long as it starts like one:
.
<div *???-&&&-<---
*foo*
.
<div *???-&&&-<---
*foo*
.
In type 6 blocks, the initial tag need not be on a line by
itself:
.
<div><a href="bar">*foo*</a></div>
.
<div><a href="bar">*foo*</a></div>
.
.
<table><tr><td>
foo
</td></tr></table>
.
<table><tr><td>
foo
</td></tr></table>
.
Everything until the next blank line or end of document
gets included in the HTML block. So, in the following
example, what looks like a Markdown code block
is actually part of the HTML block, which continues until a blank
line or the end of the document is reached:
.
<div></div>
``` c
int x = 33;
```
.
<div></div>
``` c
int x = 33;
```
.
To start an [HTML block] with a tag that is *not* in the
list of block-level tags in (6), you must put the tag by
itself on the first line (and it must be complete):
.
<a href="foo">
*bar*
</a>
.
<a href="foo">
*bar*
</a>
.
In type 7 blocks, the [tag name] can be anything:
.
<Warning>
*bar*
</Warning>
.
<Warning>
*bar*
</Warning>
.
.
<i class="foo">
*bar*
</i>
.
<i class="foo">
*bar*
</i>
.
.
</ins>
*bar*
.
</ins>
*bar*
.
These rules are designed to allow us to work with tags that
can function as either block-level or inline-level tags.
The `<del>` tag is a nice example. We can surround content with
`<del>` tags in three different ways. In this case, we get a raw
HTML block, because the `<del>` tag is on a line by itself:
.
<del>
*foo*
</del>
.
<del>
*foo*
</del>
.
In this case, we get a raw HTML block that just includes
the `<del>` tag (because it ends with the following blank
line). So the contents get interpreted as CommonMark:
.
<del>
*foo*
</del>
.
<del>
<p><em>foo</em></p>
</del>
.
Finally, in this case, the `<del>` tags are interpreted
as [raw HTML] *inside* the CommonMark paragraph. (Because
the tag is not on a line by itself, we get inline HTML
rather than an [HTML block].)
.
<del>*foo*</del>
.
<p><del><em>foo</em></del></p>
.
HTML tags designed to contain literal content
(`script`, `style`, `pre`), comments, processing instructions,
and declarations are treated somewhat differently.
Instead of ending at the first blank line, these blocks
end at the first line containing a corresponding end tag.
As a result, these blocks can contain blank lines:
A pre tag (type 1):
.
<pre language="haskell"><code>
import Text.HTML.TagSoup
main :: IO ()
main = print $ parseTags tags
</code></pre>
.
<pre language="haskell"><code>
import Text.HTML.TagSoup
main :: IO ()
main = print $ parseTags tags
</code></pre>
.
A script tag (type 1):
.
<script type="text/javascript">
// JavaScript example
document.getElementById("demo").innerHTML = "Hello JavaScript!";
</script>
.
<script type="text/javascript">
// JavaScript example
document.getElementById("demo").innerHTML = "Hello JavaScript!";
</script>
.
A style tag (type 1):
.
<style
type="text/css">
h1 {color:red;}
p {color:blue;}
</style>
.
<style
type="text/css">
h1 {color:red;}
p {color:blue;}
</style>
.
If there is no matching end tag, the block will end at the
end of the document (or the enclosing [block quote] or
[list item]):
.
<style
type="text/css">
foo
.
<style
type="text/css">
foo
.
.
> <div>
> foo
bar
.
<blockquote>
<div>
foo
</blockquote>
<p>bar</p>
.
.
- <div>
- foo
.
<ul>
<li>
<div>
</li>
<li>foo</li>
</ul>
.
The end tag can occur on the same line as the start tag:
.
<style>p{color:red;}</style>
*foo*
.
<style>p{color:red;}</style>
<p><em>foo</em></p>
.
.
<!-- foo -->*bar*
*baz*
.
<!-- foo -->*bar*
<p><em>baz</em></p>
.
Note that anything on the last line after the
end tag will be included in the [HTML block]:
.
<script>
foo
</script>1. *bar*
.
<script>
foo
</script>1. *bar*
.
A comment (type 2):
.
<!-- Foo
bar
baz -->
.
<!-- Foo
bar
baz -->
.
A processing instruction (type 3):
.
<?php
echo '>';
?>
.
<?php
echo '>';
?>
.
A declaration (type 4):
.
<!DOCTYPE html>
.
<!DOCTYPE html>
.
CDATA (type 5):
.
<![CDATA[
function matchwo(a,b)
{
if (a < b && a < 0) then {
return 1;
} else {
return 0;
}
}
]]>
.
<![CDATA[
function matchwo(a,b)
{
if (a < b && a < 0) then {
return 1;
} else {
return 0;
}
}
]]>
.
The opening tag can be indented 1-3 spaces, but not 4:
.
<!-- foo -->
<!-- foo -->
.
<!-- foo -->
<pre><code>&lt;!-- foo --&gt;
</code></pre>
.
.
<div>
<div>
.
<div>
<pre><code>&lt;div&gt;
</code></pre>
.
An HTML block of types 1--6 can interrupt a paragraph, and need not be
preceded by a blank line.
.
Foo
<div>
bar
</div>
.
<p>Foo</p>
<div>
bar
</div>
.
However, a following blank line is needed, except at the end of
a document, and except for blocks of types 1--5, above:
.
<div>
bar
</div>
*foo*
.
<div>
bar
</div>
*foo*
.
HTML blocks of type 7 cannot interrupt a paragraph:
.
Foo
<a href="bar">
baz
.
<p>Foo
<a href="bar">
baz</p>
.
This rule differs from John Gruber's original Markdown syntax
specification, which says:
> The only restrictions are that block-level HTML elements —
> e.g. `<div>`, `<table>`, `<pre>`, `<p>`, etc. — must be separated from
> surrounding content by blank lines, and the start and end tags of the
> block should not be indented with tabs or spaces.
In some ways Gruber's rule is more restrictive than the one given
here:
- It requires that an HTML block be preceded by a blank line.
- It does not allow the start tag to be indented.
- It requires a matching end tag, which it also does not allow to
be indented.
Most Markdown implementations (including some of Gruber's own) do not
respect all of these restrictions.
There is one respect, however, in which Gruber's rule is more liberal
than the one given here, since it allows blank lines to occur inside
an HTML block. There are two reasons for disallowing them here.
First, it removes the need to parse balanced tags, which is
expensive and can require backtracking from the end of the document
if no matching end tag is found. Second, it provides a very simple
and flexible way of including Markdown content inside HTML tags:
simply separate the Markdown from the HTML using blank lines:
Compare:
.
<div>
*Emphasized* text.
</div>
.
<div>
<p><em>Emphasized</em> text.</p>
</div>
.
.
<div>
*Emphasized* text.
</div>
.
<div>
*Emphasized* text.
</div>
.
Some Markdown implementations have adopted a convention of
interpreting content inside tags as text if the open tag has
the attribute `markdown=1`. The rule given above seems a simpler and
more elegant way of achieving the same expressive power, which is also
much simpler to parse.
The main potential drawback is that one can no longer paste HTML
blocks into Markdown documents with 100% reliability. However,
*in most cases* this will work fine, because the blank lines in
HTML are usually followed by HTML block tags. For example:
.
<table>
<tr>
<td>
Hi
</td>
</tr>
</table>
.
<table>
<tr>
<td>
Hi
</td>
</tr>
</table>
.
There are problems, however, if the inner tags are indented
*and* separated by spaces, as then they will be interpreted as
an indented code block:
.
<table>
<tr>
<td>
Hi
</td>
</tr>
</table>
.
<table>
<tr>
<pre><code>&lt;td&gt;
Hi
&lt;/td&gt;
</code></pre>
</tr>
</table>
.
Fortunately, blank lines are usually not necessary and can be
deleted. The exception is inside `<pre>` tags, but as described
above, raw HTML blocks starting with `<pre>` *can* contain blank
lines.
## Link reference definitions
A [link reference definition](@link-reference-definition)
consists of a [link label], indented up to three spaces, followed
by a colon (`:`), optional [whitespace] (including up to one
[line ending]), a [link destination],
optional [whitespace] (including up to one
[line ending]), and an optional [link
title], which if it is present must be separated
from the [link destination] by [whitespace].
No further [non-whitespace character]s may occur on the line.
A [link reference definition]
does not correspond to a structural element of a document. Instead, it
defines a label which can be used in [reference link]s
and reference-style [images] elsewhere in the document. [Link
reference definitions] can come either before or after the links that use
them.
.
[foo]: /url "title"
[foo]
.
<p><a href="/url" title="title">foo</a></p>
.
.
[foo]:
/url
'the title'
[foo]
.
<p><a href="/url" title="the title">foo</a></p>
.
.
[Foo*bar\]]:my_(url) 'title (with parens)'
[Foo*bar\]]
.
<p><a href="my_(url)" title="title (with parens)">Foo*bar]</a></p>
.
.
[Foo bar]:
<my url>
'title'
[Foo bar]
.
<p><a href="my%20url" title="title">Foo bar</a></p>
.
The title may extend over multiple lines:
.
[foo]: /url '
title
line1
line2
'
[foo]
.
<p><a href="/url" title="
title
line1
line2
">foo</a></p>
.
However, it may not contain a [blank line]:
.
[foo]: /url 'title
with blank line'
[foo]
.
<p>[foo]: /url 'title</p>
<p>with blank line'</p>
<p>[foo]</p>
.
The title may be omitted:
.
[foo]:
/url
[foo]
.
<p><a href="/url">foo</a></p>
.
The link destination may not be omitted:
.
[foo]:
[foo]
.
<p>[foo]:</p>
<p>[foo]</p>
.
Both title and destination can contain backslash escapes
and literal backslashes:
.
[foo]: /url\bar\*baz "foo\"bar\baz"
[foo]
.
<p><a href="/url%5Cbar*baz" title="foo&quot;bar\baz">foo</a></p>
.
A link can come before its corresponding definition:
.
[foo]
[foo]: url
.
<p><a href="url">foo</a></p>
.
If there are several matching definitions, the first one takes
precedence:
.
[foo]
[foo]: first
[foo]: second
.
<p><a href="first">foo</a></p>
.
As noted in the section on [Links], matching of labels is
case-insensitive (see [matches]).
.
[FOO]: /url
[Foo]
.
<p><a href="/url">Foo</a></p>
.
.
[ΑΓΩ]: /φου
[αγω]
.
<p><a href="/%CF%86%CE%BF%CF%85">αγω</a></p>
.
Here is a link reference definition with no corresponding link.
It contributes nothing to the document.
.
[foo]: /url
.
.
Here is another one:
.
[
foo
]: /url
bar
.
<p>bar</p>
.
This is not a link reference definition, because there are
[non-whitespace character]s after the title:
.
[foo]: /url "title" ok
.
<p>[foo]: /url &quot;title&quot; ok</p>
.
This is a link reference definition, but it has no title:
.
[foo]: /url
"title" ok
.
<p>&quot;title&quot; ok</p>
.
This is not a link reference definition, because it is indented
four spaces:
.
[foo]: /url "title"
[foo]
.
<pre><code>[foo]: /url &quot;title&quot;
</code></pre>
<p>[foo]</p>
.
This is not a link reference definition, because it occurs inside
a code block:
.
```
[foo]: /url
```
[foo]
.
<pre><code>[foo]: /url
</code></pre>
<p>[foo]</p>
.
A [link reference definition] cannot interrupt a paragraph.
.
Foo
[bar]: /baz
[bar]
.
<p>Foo
[bar]: /baz</p>
<p>[bar]</p>
.
However, it can directly follow other block elements, such as headers
and horizontal rules, and it need not be followed by a blank line.
.
# [Foo]
[foo]: /url
> bar
.
<h1><a href="/url">Foo</a></h1>
<blockquote>
<p>bar</p>
</blockquote>
.
Several [link reference definition]s
can occur one after another, without intervening blank lines.
.
[foo]: /foo-url "foo"
[bar]: /bar-url
"bar"
[baz]: /baz-url
[foo],
[bar],
[baz]
.
<p><a href="/foo-url" title="foo">foo</a>,
<a href="/bar-url" title="bar">bar</a>,
<a href="/baz-url">baz</a></p>
.
[Link reference definition]s can occur
inside block containers, like lists and block quotations. They
affect the entire document, not just the container in which they
are defined:
.
[foo]
> [foo]: /url
.
<p><a href="/url">foo</a></p>
<blockquote>
</blockquote>
.
## Paragraphs
A sequence of non-blank lines that cannot be interpreted as other
kinds of blocks forms a [paragraph](@paragraph).
The contents of the paragraph are the result of parsing the
paragraph's raw content as inlines. The paragraph's raw content
is formed by concatenating the lines and removing initial and final
[whitespace].
A simple example with two paragraphs:
.
aaa
bbb
.
<p>aaa</p>
<p>bbb</p>
.
Paragraphs can contain multiple lines, but no blank lines:
.
aaa
bbb
ccc
ddd
.
<p>aaa
bbb</p>
<p>ccc
ddd</p>
.
Multiple blank lines between paragraph have no effect:
.
aaa
bbb
.
<p>aaa</p>
<p>bbb</p>
.
Leading spaces are skipped:
.
aaa
bbb
.
<p>aaa
bbb</p>
.
Lines after the first may be indented any amount, since indented
code blocks cannot interrupt paragraphs.
.
aaa
bbb
ccc
.
<p>aaa
bbb
ccc</p>
.
However, the first line may be indented at most three spaces,
or an indented code block will be triggered:
.
aaa
bbb
.
<p>aaa
bbb</p>
.
.
aaa
bbb
.
<pre><code>aaa
</code></pre>
<p>bbb</p>
.
Final spaces are stripped before inline parsing, so a paragraph
that ends with two or more spaces will not end with a [hard line
break]:
.
aaa
bbb
.
<p>aaa<br />
bbb</p>
.
## Blank lines
[Blank line]s between block-level elements are ignored,
except for the role they play in determining whether a [list]
is [tight] or [loose].
Blank lines at the beginning and end of the document are also ignored.
.
aaa
# aaa
.
<p>aaa</p>
<h1>aaa</h1>
.
# Container blocks
A [container block] is a block that has other
blocks as its contents. There are two basic kinds of container blocks:
[block quotes] and [list items].
[Lists] are meta-containers for [list items].
We define the syntax for container blocks recursively. The general
form of the definition is:
> If X is a sequence of blocks, then the result of
> transforming X in such-and-such a way is a container of type Y
> with these blocks as its content.
So, we explain what counts as a block quote or list item by explaining
how these can be *generated* from their contents. This should suffice
to define the syntax, although it does not give a recipe for *parsing*
these constructions. (A recipe is provided below in the section entitled
[A parsing strategy](#appendix-a-parsing-strategy).)
## Block quotes
A [block quote marker](@block-quote-marker)
consists of 0-3 spaces of initial indent, plus (a) the character `>` together
with a following space, or (b) a single character `>` not followed by a space.
The following rules define [block quotes]:
1. **Basic case.** If a string of lines *Ls* constitute a sequence
of blocks *Bs*, then the result of prepending a [block quote
marker] to the beginning of each line in *Ls*
is a [block quote](#block-quotes) containing *Bs*.
2. **Laziness.** If a string of lines *Ls* constitute a [block
quote](#block-quotes) with contents *Bs*, then the result of deleting
the initial [block quote marker] from one or
more lines in which the next [non-whitespace character] after the [block
quote marker] is [paragraph continuation
text] is a block quote with *Bs* as its content.
[Paragraph continuation text](@paragraph-continuation-text) is text
that will be parsed as part of the content of a paragraph, but does
not occur at the beginning of the paragraph.
3. **Consecutiveness.** A document cannot contain two [block
quotes] in a row unless there is a [blank line] between them.
Nothing else counts as a [block quote](#block-quotes).
Here is a simple example:
.
> # Foo
> bar
> baz
.
<blockquote>
<h1>Foo</h1>
<p>bar
baz</p>
</blockquote>
.
The spaces after the `>` characters can be omitted:
.
># Foo
>bar
> baz
.
<blockquote>
<h1>Foo</h1>
<p>bar
baz</p>
</blockquote>
.
The `>` characters can be indented 1-3 spaces:
.
> # Foo
> bar
> baz
.
<blockquote>
<h1>Foo</h1>
<p>bar
baz</p>
</blockquote>
.
Four spaces gives us a code block:
.
> # Foo
> bar
> baz
.
<pre><code>&gt; # Foo
&gt; bar
&gt; baz
</code></pre>
.
The Laziness clause allows us to omit the `>` before a
paragraph continuation line:
.
> # Foo
> bar
baz
.
<blockquote>
<h1>Foo</h1>
<p>bar
baz</p>
</blockquote>
.
A block quote can contain some lazy and some non-lazy
continuation lines:
.
> bar
baz
> foo
.
<blockquote>
<p>bar
baz
foo</p>
</blockquote>
.
Laziness only applies to lines that would have been continuations of
paragraphs had they been prepended with [block quote marker]s.
For example, the `> ` cannot be omitted in the second line of
``` markdown
> foo
> ---
```
without changing the meaning:
.
> foo
---
.
<blockquote>
<p>foo</p>
</blockquote>
<hr />
.
Similarly, if we omit the `> ` in the second line of
``` markdown
> - foo
> - bar
```
then the block quote ends after the first line:
.
> - foo
- bar
.
<blockquote>
<ul>
<li>foo</li>
</ul>
</blockquote>
<ul>
<li>bar</li>
</ul>
.
For the same reason, we can't omit the `> ` in front of
subsequent lines of an indented or fenced code block:
.
> foo
bar
.
<blockquote>
<pre><code>foo
</code></pre>
</blockquote>
<pre><code>bar
</code></pre>
.
.
> ```
foo
```
.
<blockquote>
<pre><code></code></pre>
</blockquote>
<p>foo</p>
<pre><code></code></pre>
.
Note that in the following case, we have a paragraph
continuation line:
.
> foo
- bar
.
<blockquote>
<p>foo
- bar</p>
</blockquote>
.
To see why, note that in
```markdown
> foo
> - bar
```
the `- bar` is indented too far to start a list, and can't
be an indented code block because indented code blocks cannot
interrupt paragraphs, so it is a [paragraph continuation line].
A block quote can be empty:
.
>
.
<blockquote>
</blockquote>
.
.
>
>
>
.
<blockquote>
</blockquote>
.
A block quote can have initial or final blank lines:
.
>
> foo
>
.
<blockquote>
<p>foo</p>
</blockquote>
.
A blank line always separates block quotes:
.
> foo
> bar
.
<blockquote>
<p>foo</p>
</blockquote>
<blockquote>
<p>bar</p>
</blockquote>
.
(Most current Markdown implementations, including John Gruber's
original `Markdown.pl`, will parse this example as a single block quote
with two paragraphs. But it seems better to allow the author to decide
whether two block quotes or one are wanted.)
Consecutiveness means that if we put these block quotes together,
we get a single block quote:
.
> foo
> bar
.
<blockquote>
<p>foo
bar</p>
</blockquote>
.
To get a block quote with two paragraphs, use:
.
> foo
>
> bar
.
<blockquote>
<p>foo</p>
<p>bar</p>
</blockquote>
.
Block quotes can interrupt paragraphs:
.
foo
> bar
.
<p>foo</p>
<blockquote>
<p>bar</p>
</blockquote>
.
In general, blank lines are not needed before or after block
quotes:
.
> aaa
***
> bbb
.
<blockquote>
<p>aaa</p>
</blockquote>
<hr />
<blockquote>
<p>bbb</p>
</blockquote>
.
However, because of laziness, a blank line is needed between
a block quote and a following paragraph:
.
> bar
baz
.
<blockquote>
<p>bar
baz</p>
</blockquote>
.
.
> bar
baz
.
<blockquote>
<p>bar</p>
</blockquote>
<p>baz</p>
.
.
> bar
>
baz
.
<blockquote>
<p>bar</p>
</blockquote>
<p>baz</p>
.
It is a consequence of the Laziness rule that any number
of initial `>`s may be omitted on a continuation line of a
nested block quote:
.
> > > foo
bar
.
<blockquote>
<blockquote>
<blockquote>
<p>foo
bar</p>
</blockquote>
</blockquote>
</blockquote>
.
.
>>> foo
> bar
>>baz
.
<blockquote>
<blockquote>
<blockquote>
<p>foo
bar
baz</p>
</blockquote>
</blockquote>
</blockquote>
.
When including an indented code block in a block quote,
remember that the [block quote marker] includes
both the `>` and a following space. So *five spaces* are needed after
the `>`:
.
> code
> not code
.
<blockquote>
<pre><code>code
</code></pre>
</blockquote>
<blockquote>
<p>not code</p>
</blockquote>
.
## List items
A [list marker](@list-marker) is a
[bullet list marker] or an [ordered list marker].
A [bullet list marker](@bullet-list-marker)
is a `-`, `+`, or `*` character.
An [ordered list marker](@ordered-list-marker)
is a sequence of 1--9 arabic digits (`0-9`), followed by either a
`.` character or a `)` character. (The reason for the length
limit is that with 10 digits we start seeing integer overflows
in some browsers.)
The following rules define [list items]:
1. **Basic case.** If a sequence of lines *Ls* constitute a sequence of
blocks *Bs* starting with a [non-whitespace character] and not separated
from each other by more than one blank line, and *M* is a list
marker of width *W* followed by 0 < *N* < 5 spaces, then the result
of prepending *M* and the following spaces to the first line of
*Ls*, and indenting subsequent lines of *Ls* by *W + N* spaces, is a
list item with *Bs* as its contents. The type of the list item
(bullet or ordered) is determined by the type of its list marker.
If the list item is ordered, then it is also assigned a start
number, based on the ordered list marker.
For example, let *Ls* be the lines
.
A paragraph
with two lines.
indented code
> A block quote.
.
<p>A paragraph
with two lines.</p>
<pre><code>indented code
</code></pre>
<blockquote>
<p>A block quote.</p>
</blockquote>
.
And let *M* be the marker `1.`, and *N* = 2. Then rule #1 says
that the following is an ordered list item with start number 1,
and the same contents as *Ls*:
.
1. A paragraph
with two lines.
indented code
> A block quote.
.
<ol>
<li>
<p>A paragraph
with two lines.</p>
<pre><code>indented code
</code></pre>
<blockquote>
<p>A block quote.</p>
</blockquote>
</li>
</ol>
.
The most important thing to notice is that the position of
the text after the list marker determines how much indentation
is needed in subsequent blocks in the list item. If the list
marker takes up two spaces, and there are three spaces between
the list marker and the next [non-whitespace character], then blocks
must be indented five spaces in order to fall under the list
item.
Here are some examples showing how far content must be indented to be
put under the list item:
.
- one
two
.
<ul>
<li>one</li>
</ul>
<p>two</p>
.
.
- one
two
.
<ul>
<li>
<p>one</p>
<p>two</p>
</li>
</ul>
.
.
- one
two
.
<ul>
<li>one</li>
</ul>
<pre><code> two
</code></pre>
.
.
- one
two
.
<ul>
<li>
<p>one</p>
<p>two</p>
</li>
</ul>
.
It is tempting to think of this in terms of columns: the continuation
blocks must be indented at least to the column of the first
[non-whitespace character] after the list marker. However, that is not quite right.
The spaces after the list marker determine how much relative indentation
is needed. Which column this indentation reaches will depend on
how the list item is embedded in other constructions, as shown by
this example:
.
> > 1. one
>>
>> two
.
<blockquote>
<blockquote>
<ol>
<li>
<p>one</p>
<p>two</p>
</li>
</ol>
</blockquote>
</blockquote>
.
Here `two` occurs in the same column as the list marker `1.`,
but is actually contained in the list item, because there is
sufficient indentation after the last containing blockquote marker.
The converse is also possible. In the following example, the word `two`
occurs far to the right of the initial text of the list item, `one`, but
it is not considered part of the list item, because it is not indented
far enough past the blockquote marker:
.
>>- one
>>
> > two
.
<blockquote>
<blockquote>
<ul>
<li>one</li>
</ul>
<p>two</p>
</blockquote>
</blockquote>
.
Note that at least one space is needed between the list marker and
any following content, so these are not list items:
.
-one
2.two
.
<p>-one</p>
<p>2.two</p>
.
A list item may not contain blocks that are separated by more than
one blank line. Thus, two blank lines will end a list, unless the
two blanks are contained in a [fenced code block].
.
- foo
bar
- foo
bar
- ```
foo
bar
```
- baz
+ ```
foo
bar
```
.
<ul>
<li>
<p>foo</p>
<p>bar</p>
</li>
<li>
<p>foo</p>
</li>
</ul>
<p>bar</p>
<ul>
<li>
<pre><code>foo
bar
</code></pre>
</li>
<li>
<p>baz</p>
<ul>
<li>
<pre><code>foo
bar
</code></pre>
</li>
</ul>
</li>
</ul>
.
A list item may contain any kind of block:
.
1. foo
```
bar
```
baz
> bam
.
<ol>
<li>
<p>foo</p>
<pre><code>bar
</code></pre>
<p>baz</p>
<blockquote>
<p>bam</p>
</blockquote>
</li>
</ol>
.
Note that ordered list start numbers must be nine digits or less:
.
123456789. ok
.
<ol start="123456789">
<li>ok</li>
</ol>
.
.
1234567890. not ok
.
<p>1234567890. not ok</p>
.
A start number may begin with 0s:
.
0. ok
.
<ol start="0">
<li>ok</li>
</ol>
.
.
003. ok
.
<ol start="3">
<li>ok</li>
</ol>
.
A start number may not be negative:
.
-1. not ok
.
<p>-1. not ok</p>
.
2. **Item starting with indented code.** If a sequence of lines *Ls*
constitute a sequence of blocks *Bs* starting with an indented code
block and not separated from each other by more than one blank line,
and *M* is a list marker of width *W* followed by
one space, then the result of prepending *M* and the following
space to the first line of *Ls*, and indenting subsequent lines of
*Ls* by *W + 1* spaces, is a list item with *Bs* as its contents.
If a line is empty, then it need not be indented. The type of the
list item (bullet or ordered) is determined by the type of its list
marker. If the list item is ordered, then it is also assigned a
start number, based on the ordered list marker.
An indented code block will have to be indented four spaces beyond
the edge of the region where text will be included in the list item.
In the following case that is 6 spaces:
.
- foo
bar
.
<ul>
<li>
<p>foo</p>
<pre><code>bar
</code></pre>
</li>
</ul>
.
And in this case it is 11 spaces:
.
10. foo
bar
.
<ol start="10">
<li>
<p>foo</p>
<pre><code>bar
</code></pre>
</li>
</ol>
.
If the *first* block in the list item is an indented code block,
then by rule #2, the contents must be indented *one* space after the
list marker:
.
indented code
paragraph
more code
.
<pre><code>indented code
</code></pre>
<p>paragraph</p>
<pre><code>more code
</code></pre>
.
.
1. indented code
paragraph
more code
.
<ol>
<li>
<pre><code>indented code
</code></pre>
<p>paragraph</p>
<pre><code>more code
</code></pre>
</li>
</ol>
.
Note that an additional space indent is interpreted as space
inside the code block:
.
1. indented code
paragraph
more code
.
<ol>
<li>
<pre><code> indented code
</code></pre>
<p>paragraph</p>
<pre><code>more code
</code></pre>
</li>
</ol>
.
Note that rules #1 and #2 only apply to two cases: (a) cases
in which the lines to be included in a list item begin with a
[non-whitespace character], and (b) cases in which
they begin with an indented code
block. In a case like the following, where the first block begins with
a three-space indent, the rules do not allow us to form a list item by
indenting the whole thing and prepending a list marker:
.
foo
bar
.
<p>foo</p>
<p>bar</p>
.
.
- foo
bar
.
<ul>
<li>foo</li>
</ul>
<p>bar</p>
.
This is not a significant restriction, because when a block begins
with 1-3 spaces indent, the indentation can always be removed without
a change in interpretation, allowing rule #1 to be applied. So, in
the above case:
.
- foo
bar
.
<ul>
<li>
<p>foo</p>
<p>bar</p>
</li>
</ul>
.
3. **Item starting with a blank line.** If a sequence of lines *Ls*
starting with a single [blank line] constitute a (possibly empty)
sequence of blocks *Bs*, not separated from each other by more than
one blank line, and *M* is a list marker of width *W*,
then the result of prepending *M* to the first line of *Ls*, and
indenting subsequent lines of *Ls* by *W + 1* spaces, is a list
item with *Bs* as its contents.
If a line is empty, then it need not be indented. The type of the
list item (bullet or ordered) is determined by the type of its list
marker. If the list item is ordered, then it is also assigned a
start number, based on the ordered list marker.
Here are some list items that start with a blank line but are not empty:
.
-
foo
-
```
bar
```
-
baz
.
<ul>
<li>foo</li>
<li>
<pre><code>bar
</code></pre>
</li>
<li>
<pre><code>baz
</code></pre>
</li>
</ul>
.
A list item can begin with at most one blank line.
In the following example, `foo` is not part of the list
item:
.
-
foo
.
<ul>
<li></li>
</ul>
<p>foo</p>
.
Here is an empty bullet list item:
.
- foo
-
- bar
.
<ul>
<li>foo</li>
<li></li>
<li>bar</li>
</ul>
.
It does not matter whether there are spaces following the [list marker]:
.
- foo
-
- bar
.
<ul>
<li>foo</li>
<li></li>
<li>bar</li>
</ul>
.
Here is an empty ordered list item:
.
1. foo
2.
3. bar
.
<ol>
<li>foo</li>
<li></li>
<li>bar</li>
</ol>
.
A list may start or end with an empty list item:
.
*
.
<ul>
<li></li>
</ul>
.
4. **Indentation.** If a sequence of lines *Ls* constitutes a list item
according to rule #1, #2, or #3, then the result of indenting each line
of *Ls* by 1-3 spaces (the same for each line) also constitutes a
list item with the same contents and attributes. If a line is
empty, then it need not be indented.
Indented one space:
.
1. A paragraph
with two lines.
indented code
> A block quote.
.
<ol>
<li>
<p>A paragraph
with two lines.</p>
<pre><code>indented code
</code></pre>
<blockquote>
<p>A block quote.</p>
</blockquote>
</li>
</ol>
.
Indented two spaces:
.
1. A paragraph
with two lines.
indented code
> A block quote.
.
<ol>
<li>
<p>A paragraph
with two lines.</p>
<pre><code>indented code
</code></pre>
<blockquote>
<p>A block quote.</p>
</blockquote>
</li>
</ol>
.
Indented three spaces:
.
1. A paragraph
with two lines.
indented code
> A block quote.
.
<ol>
<li>
<p>A paragraph
with two lines.</p>
<pre><code>indented code
</code></pre>
<blockquote>
<p>A block quote.</p>
</blockquote>
</li>
</ol>
.
Four spaces indent gives a code block:
.
1. A paragraph
with two lines.
indented code
> A block quote.
.
<pre><code>1. A paragraph
with two lines.
indented code
&gt; A block quote.
</code></pre>
.
5. **Laziness.** If a string of lines *Ls* constitute a [list
item](#list-items) with contents *Bs*, then the result of deleting
some or all of the indentation from one or more lines in which the
next [non-whitespace character] after the indentation is
[paragraph continuation text] is a
list item with the same contents and attributes. The unindented
lines are called
[lazy continuation line](@lazy-continuation-line)s.
Here is an example with [lazy continuation line]s:
.
1. A paragraph
with two lines.
indented code
> A block quote.
.
<ol>
<li>
<p>A paragraph
with two lines.</p>
<pre><code>indented code
</code></pre>
<blockquote>
<p>A block quote.</p>
</blockquote>
</li>
</ol>
.
Indentation can be partially deleted:
.
1. A paragraph
with two lines.
.
<ol>
<li>A paragraph
with two lines.</li>
</ol>
.
These examples show how laziness can work in nested structures:
.
> 1. > Blockquote
continued here.
.
<blockquote>
<ol>
<li>
<blockquote>
<p>Blockquote
continued here.</p>
</blockquote>
</li>
</ol>
</blockquote>
.
.
> 1. > Blockquote
> continued here.
.
<blockquote>
<ol>
<li>
<blockquote>
<p>Blockquote
continued here.</p>
</blockquote>
</li>
</ol>
</blockquote>
.
6. **That's all.** Nothing that is not counted as a list item by rules
#1--5 counts as a [list item](#list-items).
The rules for sublists follow from the general rules above. A sublist
must be indented the same number of spaces a paragraph would need to be
in order to be included in the list item.
So, in this case we need two spaces indent:
.
- foo
- bar
- baz
.
<ul>
<li>foo
<ul>
<li>bar
<ul>
<li>baz</li>
</ul>
</li>
</ul>
</li>
</ul>
.
One is not enough:
.
- foo
- bar
- baz
.
<ul>
<li>foo</li>
<li>bar</li>
<li>baz</li>
</ul>
.
Here we need four, because the list marker is wider:
.
10) foo
- bar
.
<ol start="10">
<li>foo
<ul>
<li>bar</li>
</ul>
</li>
</ol>