Lists

A list (opens new window) is a sequence of one or more list items of the same type (opens new window). The list items may be separated by any number of blank lines.
Two list items are of the same type (opens new window) if they begin with a list marker (opens new window) of the same type. Two list markers are of the same type if (a) they are bullet list markers using the same character (-, +, or *) or (b) they are ordered list numbers with the same delimiter (either . or )).
A list is an ordered list (opens new window) if its constituent list items begin with ordered list markers (opens new window), and a bullet list (opens new window) if its constituent list items begin with bullet list markers (opens new window).
The start number (opens new window) of an ordered list (opens new window) is determined by the list number of its initial list item. The numbers of subsequent list items are disregarded.
A list is loose (opens new window) if any of its constituent list items are separated by blank lines, or if any of its constituent list items directly contain two block-level elements with a blank line between them. Otherwise a list is tight (opens new window). (The difference in HTML output is that paragraphs in a loose list are wrapped in <p> tags, while paragraphs in a tight list are not.)
Changing the bullet or ordered list delimiter starts a new list:

Example 281

Markdown	HTML	Demo
- foo - bar + baz	<ul> <li>foo</li> <li>bar</li> </ul> <ul> <li>baz</li> </ul>

Example 282

Markdown	HTML	Demo
1. foo 2. bar 3) baz	<ol> <li>foo</li> <li>bar</li> </ol> <ol start="3"> <li>baz</li> </ol>

In CommonMark, a list can interrupt a paragraph. That is, no blank line is needed to separate a paragraph from a following list:

Example 283

Markdown	HTML	Demo
Foo - bar - baz	<p>Foo</p> <ul> <li>bar</li> <li>baz</li> </ul>

Markdown.pl does not allow this, through fear of triggering a list via a numeral in a hard-wrapped line:

The number of windows in my house is
14.  The number of doors is 6.

Oddly, though, Markdown.pl does allow a blockquote to interrupt a paragraph, even though the same considerations might apply.
In CommonMark, we do allow lists to interrupt paragraphs, for two reasons. First, it is natural and not uncommon for people to start lists without blank lines:

I need to buy
- new shoes
- a coat
- a plane ticket

Second, we are attracted to a

principle of uniformity (opens new window): if a chunk of text has a certain meaning, it will continue to have the same meaning when put into a container block (such as a list item or blockquote).

(Indeed, the spec for list items (opens new window) and block quotes (opens new window) presupposes this principle.) This principle implies that if

  * I need to buy
    - new shoes
    - a coat
    - a plane ticket

is a list item containing a paragraph followed by a nested sublist, as all Markdown implementations agree it is (though the paragraph may be rendered without <p> tags, since the list is “tight”), then

I need to buy
- new shoes
- a coat
- a plane ticket

by itself should be a paragraph followed by a nested sublist.
Since it is well established Markdown practice to allow lists to interrupt paragraphs inside list items, the principle of uniformity (opens new window) requires us to allow this outside list items as well. (reStructuredText (opens new window) takes a different approach, requiring blank lines before lists even inside other list items.)
In order to solve of unwanted lists in paragraphs with hard-wrapped numerals, we allow only lists starting with 1 to interrupt paragraphs. Thus,

Example 284

Markdown	HTML	Demo
The number of windows in my house is 14. The number of doors is 6.	<p>The number of windows in my house is 14. The number of doors is 6.</p>

We may still get an unintended result in cases like

Example 285

Markdown	HTML	Demo
The number of windows in my house is 1. The number of doors is 6.	<p>The number of windows in my house is</p> <ol> <li>The number of doors is 6.</li> </ol>

but this rule should prevent most spurious list captures.
There can be any number of blank lines between items:

Example 286

Markdown	HTML	Demo
- foo - bar - baz	<ul> <li> <p>foo</p> </li> <li> <p>bar</p> </li> <li> <p>baz</p> </li> </ul>

Example 287

Markdown	HTML	Demo
- foo - bar - baz bim	<ul> <li>foo <ul> <li>bar <ul> <li> <p>baz</p> <p>bim</p> </li> </ul> </li> </ul> </li> </ul>

To separate consecutive lists of the same type, or to separate a list from an indented code block that would otherwise be parsed as a subparagraph of the final list item, you can insert a blank HTML comment:

Example 288

Markdown	HTML	Demo
- foo - bar <!-- --> - baz - bim	<ul> <li>foo</li> <li>bar</li> </ul> <!-- --> <ul> <li>baz</li> <li>bim</li> </ul>

Example 289

Markdown	HTML	Demo
- foo notcode - foo <!-- --> code	<ul> <li> <p>foo</p> <p>notcode</p> </li> <li> <p>foo</p> </li> </ul> <!-- --> <pre><code>code </code></pre>

List items need not be indented to the same level. The following list items will be treated as items at the same list level, since none is indented enough to belong to the previous list item:

Example 290

Markdown	HTML	Demo
- a - b - c - d - e - f - g	<ul> <li>a</li> <li>b</li> <li>c</li> <li>d</li> <li>e</li> <li>f</li> <li>g</li> </ul>

Example 291

Markdown	HTML	Demo
1. a 2. b 3. c	<ol> <li> <p>a</p> </li> <li> <p>b</p> </li> <li> <p>c</p> </li> </ol>

Note, however, that list items may not be indented more than three spaces. Here - e is treated as a paragraph continuation line, because it is indented more than three spaces:

Example 292

Markdown	HTML	Demo
- a - b - c - d - e	<ul> <li>a</li> <li>b</li> <li>c</li> <li>d - e</li> </ul>

And here, 3. c is treated as in indented code block, because it is indented four spaces and preceded by a blank line.

Example 293

Markdown	HTML	Demo
1. a 2. b 3. c	<ol> <li> <p>a</p> </li> <li> <p>b</p> </li> </ol> <pre><code>3. c </code></pre>

This is a loose list, because there is a blank line between two of the list items:

Example 294

Markdown	HTML	Demo
- a - b - c	<ul> <li> <p>a</p> </li> <li> <p>b</p> </li> <li> <p>c</p> </li> </ul>

So is this, with a empty second item:

Example 295

Markdown	HTML	Demo
* a * * c	<ul> <li> <p>a</p> </li> <li></li> <li> <p>c</p> </li> </ul>

These are loose lists, even though there is no space between the items, because one of the items directly contains two block-level elements with a blank line between them:

Example 296

Markdown	HTML	Demo
- a - b c - d	<ul> <li> <p>a</p> </li> <li> <p>b</p> <p>c</p> </li> <li> <p>d</p> </li> </ul>

Example 297

Markdown	HTML	Demo
- a - b [ref]: /url - d	<ul> <li> <p>a</p> </li> <li> <p>b</p> </li> <li> <p>d</p> </li> </ul>

This is a tight list, because the blank lines are in a code block:

Example 298

Markdown	HTML	Demo
- a - ``` b ``` - c	<ul> <li>a</li> <li> <pre><code>b </code></pre> </li> <li>c</li> </ul>

This is a tight list, because the blank line is between two paragraphs of a sublist. So the sublist is loose while the outer list is tight:

Example 299

Markdown	HTML	Demo
- a - b c - d	<ul> <li>a <ul> <li> <p>b</p> <p>c</p> </li> </ul> </li> <li>d</li> </ul>

This is a tight list, because the blank line is inside the block quote:

Example 300

Markdown	HTML	Demo
* a > b > * c	<ul> <li>a <blockquote> <p>b</p> </blockquote> </li> <li>c</li> </ul>

This list is tight, because the consecutive block elements are not separated by blank lines:

Example 301

Markdown	HTML	Demo
- a > b ``` c ``` - d	<ul> <li>a <blockquote> <p>b</p> </blockquote> <pre><code>c </code></pre> </li> <li>d</li> </ul>

A single-paragraph list is tight:

Example 302

Markdown	HTML	Demo
- a	<ul> <li>a</li> </ul>

Example 303

Markdown	HTML	Demo
- a - b	<ul> <li>a <ul> <li>b</li> </ul> </li> </ul>

This list is loose, because of the blank line between the two block elements in the list item:

Example 304

Markdown	HTML	Demo
1. ``` foo ``` bar	<ol> <li> <pre><code>foo </code></pre> <p>bar</p> </li> </ol>

Here the outer list is loose, the inner list tight:

Example 305

Markdown	HTML	Demo
* foo * bar baz	<ul> <li> <p>foo</p> <ul> <li>bar</li> </ul> <p>baz</p> </li> </ul>

Example 306

Markdown	HTML	Demo
- a - b - c - d - e - f	<ul> <li> <p>a</p> <ul> <li>b</li> <li>c</li> </ul> </li> <li> <p>d</p> <ul> <li>e</li> <li>f</li> </ul> </li> </ul>