Markdown 基本语法

在 John Gruber 设计文档中列出的所有 Markdown 元素。

总览

几乎所有 Markdown 应用程序都支持 John Gruber 原始设计文档中列出的 Markdown 基本语法。但是,Markdown 处理程序之间存在着细微的变化和差异,我们都会尽可能标记出来。

标题(Headings)

要创建标题,请在单词或短语前面添加井号 (#) 。井号的数量代表了标题的级别。例如,添加三个井号即创建一个三级标题 (<h3>) (例如:### My Header)。

Markdown HTML 渲染效果
# Heading level 1 <h1>Heading level 1</h1>

Heading level 1

## Heading level 2 <h2>Heading level 2</h2>

Heading level 2

### Heading level 3 <h3>Heading level 3</h3>

Heading level 3

#### Heading level 4 <h4>Heading level 4</h4>

Heading level 4

##### Heading level 5 <h5>Heading level 5</h5>
Heading level 5
###### Heading level 6 <h6>Heading level 6</h6>
Heading level 6

可选语法

还可以在文本下方添加任意数量的 == 号来标识一级标题,或者 -- 号来标识二级标题。

Markdown HTML 渲染效果
Heading level 1
===============
<h1>Heading level 1</h1>

Heading level 1

Heading level 2
---------------
<h2>Heading level 2</h2>

Heading level 2

标题(Heading)用法的最佳实践

Markdown 应用程序在处理标题和周围段落之间紧挨着的情况时并不一致。为了兼容考虑,请用一个或多个空白行对段落和标题进行分隔。

✅  这样做 ❌  不要这样做
This is a paragraph.

# Here's the heading

And this is another paragraph.
This is a paragraph.
# Here's the heading
And this is another paragraph.

段落(Paragraphs)

要创建段落,请使用空白行将一行或多行文本进行分隔。

Markdown HTML 渲染效果
I really like using Markdown.

I think I'll use it to format all of my documents from now on.
<p>I really like using Markdown.</p>

<p>I think I'll use it to format all of my documents from now on.</p>

I really like using Markdown.

I think I'll use it to format all of my documents from now on.

段落(Paragraph)用法的最佳实践

不要用空格(spaces)或制表符( tabs)缩进段落。

✅  这样做 ❌  不要这样做
Don't put tabs or spaces in front of your paragraphs.

Keep lines left-aligned like this.

    This can result in unexpected formatting problems.

  Don't add tabs or spaces in front of paragraphs.

换行(Line Breaks)

在一行的末尾添加两个或多个空格,然后按回车键(return),即可创建一个换行(line break) (<br>)。

Markdown HTML 渲染效果
This is the first line.  
And this is the second line.
<p>This is the first line.<br>
And this is the second line.</p>

This is the first line.
And this is the second line.

换行(Line Break)用法的最佳实践

几乎每个 Markdown 应用程序都支持两个或多个空格进行换行 (称为 “结尾空格(trailing whitespace)”) 的方式,但这是有争议的,因为很难在编辑器中直接看到空格,并且很多人在每个句子后面都会有意或无意地添加两个空格。由于这个原因,你可能要使用除结尾空格以外的其它方式来换行。幸运的是,几乎每个 Markdown 应用程序都支持另一种换行方式:HTML 的 <br> 标签。

为了兼容性,请在行尾添加“结尾空格”或 HTML 的 <br> 标签来实现换行。

还有两种其他方式我并不推荐使用。CommonMark 和其它几种轻量级标记语言支持在行尾添加反斜杠 (\) 的方式实现换行,但是并非所有 Markdown 应用程序都支持此种方式,因此从兼容性的角度来看,不推荐使用。并且至少有两种轻量级标记语言支持无须在行尾添加任何内容,只须键入回车键( return)即可实现换行。

✅  这样做 ❌  不要这样做
First line with two spaces after.  
And the next line.

First line with the HTML tag after.<br>
And the next line.

First line with a backslash after.\
And the next line.

First line with nothing after.
And the next line.

强调(Emphasis)

通过将文本设置为粗体或斜体来强调其重要性。

粗体(Bold)

要加粗文本,请在单词或短语的前后各添加两个星号(asterisks)或下划线(underscores)。如需加粗一个单词或短语的中间部分用以表示强调的话,请在要加粗部分的两侧各添加两个星号(asterisks)。

Markdown HTML 渲染效果
I just love **bold text**. I just love <strong>bold text</strong>. I just love bold text.
I just love __bold text__. I just love <strong>bold text</strong>. I just love bold text.
Love**is**bold Love<strong>is</strong>bold Loveisbold

粗体(Bold)用法最佳实践

Markdown 应用程序在如何处理单词或短语中间的下划线上并不一致。为兼容考虑,在单词或短语中间部分加粗的话,请使用星号(asterisks)。

✅  这样做 ❌  不要这样做
Love**is**bold Love__is__bold

斜体(Italic)

要用斜体显示文本,请在单词或短语前后添加一个星号(asterisk)或下划线(underscore)。要斜体突出单词的中间部分,请在字母前后各添加一个星号,中间不要带空格。

Markdown HTML 渲染效果
Italicized text is the *cat's meow*. Italicized text is the <em>cat's meow</em>. Italicized text is the cat’s meow.
Italicized text is the _cat's meow_. Italicized text is the <em>cat's meow</em>. Italicized text is the cat’s meow.
A*cat*meow A<em>cat</em>meow Acatmeow

斜体(Italic)用法的最佳实践

Markdown 的众多应用程序在如何处理单词中间的下划线上意见不一致。为了兼容起见,请用星号标注单词中间的斜体来表示着重。

✅  这样做 ❌  不要这样做
A*cat*meow A_cat_meow

粗体(Bold)和斜体(Italic)

要同时用粗体和斜体突出显示文本,请在单词或短语的前后各添加三个星号或下划线。要加粗并用斜体显示单词或短语的中间部分,请在要突出显示的部分前后各添加三个星号,中间不要带空格。

Markdown HTML 渲染效果
This text is ***really important***. This text is <strong><em>really important</em></strong>. This text is really important.
This text is ___really important___. This text is <strong><em>really important</em></strong>. This text is really important.
This text is __*really important*__. This text is <strong><em>really important</em></strong>. This text is really important.
This text is **_really important_**. This text is <strong><em>really important</em></strong>. This text is really important.
This is really***very***important text. This is really<strong><em>very</em></strong>important text. This is reallyveryimportant text.

粗体(Bold)和斜体(Italic)用法的最佳实践

Markdown 应用程序在处理单词或短语中间添加的下划线上并不一致。为了实现兼容性,请使用星号将单词或短语的中间部分加粗并以斜体显示,以示重要。

✅  这样做 ❌  不要这样做
This is really***very***important text. This is really___very___important text.

块引用(Blockquotes)

要创建块引用,请在段落前添加一个 > 符号。

> Dorothy followed her through many of the beautiful rooms in her castle.

渲染效果如下所示:

Dorothy followed her through many of the beautiful rooms in her castle.

多个段落的块引用(Blockquotes)

块引用可以包含多个段落。为段落之间的空白行各添加一个 > 符号。

> Dorothy followed her through many of the beautiful rooms in her castle.
>
> The Witch bade her clean the pots and kettles and sweep the floor and keep the fire fed with wood.

渲染效果如下:

Dorothy followed her through many of the beautiful rooms in her castle.

The Witch bade her clean the pots and kettles and sweep the floor and keep the fire fed with wood.

嵌套块引用(Nested Blockquotes)

块引用可以嵌套。在要嵌套的段落前添加一个 >> 符号。

> Dorothy followed her through many of the beautiful rooms in her castle.
>
>> The Witch bade her clean the pots and kettles and sweep the floor and keep the fire fed with wood.

渲染效果如下:

Dorothy followed her through many of the beautiful rooms in her castle.

The Witch bade her clean the pots and kettles and sweep the floor and keep the fire fed with wood.

带有其它元素的块引用(Blockquotes with Other Elements)

块引用可以包含其他 Markdown 格式的元素。并非所有元素都可以使用,你需要进行实验以查看哪些元素有效。

> #### The quarterly results look great!
>
> - Revenue was off the chart.
> - Profits were higher than ever.
>
>  *Everything* is going according to **plan**.

渲染效果如下:

The quarterly results look great!

  • Revenue was off the chart.
  • Profits were higher than ever.

Everything is going according to plan.

列表(Lists)

你可以将多个条目组织成有序或无序列表。

有序列表(Ordered Lists)

要创建有序列表,请在每个列表项前添加数字并紧跟一个英文句点。数字不必按数学顺序排列,但是列表应当以数字 1 起始。

Markdown HTML Rendered Output
1. First item
2. Second item
3. Third item
4. Fourth item
<ol>
<li>First item</li>
<li>Second item</li>
<li>Third item</li>
<li>Fourth item</li>
</ol>
  1. First item
  2. Second item
  3. Third item
  4. Fourth item
1. First item
1. Second item
1. Third item
1. Fourth item
<ol>
<li>First item</li>
<li>Second item</li>
<li>Third item</li>
<li>Fourth item</li>
</ol>
  1. First item
  2. Second item
  3. Third item
  4. Fourth item
1. First item
8. Second item
3. Third item
5. Fourth item
<ol>
<li>First item</li>
<li>Second item</li>
<li>Third item</li>
<li>Fourth item</li>
</ol>
  1. First item
  2. Second item
  3. Third item
  4. Fourth item
1. First item
2. Second item
3. Third item
    1. Indented item
    2. Indented item
4. Fourth item
<ol>
<li>First item</li>
<li>Second item</li>
<li>Third item
<ol>
<li>Indented item</li>
<li>Indented item</li>
</ol>
</li>
<li>Fourth item</li>
</ol>
  1. First item
  2. Second item
  3. Third item
    1. Indented item
    2. Indented item
  4. Fourth item

无序列表(Unordered Lists)

要创建无序列表,请在每个列表项前面添加破折号 (-)、星号 (*) 或加号 (+) 。缩进一个或多个列表项可创建嵌套列表。

Markdown HTML 渲染效果
- First item
- Second item
- Third item
- Fourth item
<ul>
<li>First item</li>
<li>Second item</li>
<li>Third item</li>
<li>Fourth item</li>
</ul>
  • First item
  • Second item
  • Third item
  • Fourth item
* First item
* Second item
* Third item
* Fourth item
<ul>
<li>First item</li>
<li>Second item</li>
<li>Third item</li>
<li>Fourth item</li>
</ul>
  • First item
  • Second item
  • Third item
  • Fourth item
+ First item
* Second item
- Third item
+ Fourth item
<ul>
<li>First item</li>
<li>Second item</li>
<li>Third item</li>
<li>Fourth item</li>
</ul>
  • First item
  • Second item
  • Third item
  • Fourth item
- First item
- Second item
- Third item
    - Indented item
    - Indented item
- Fourth item
<ul>
<li>First item</li>
<li>Second item</li>
<li>Third item
<ul>
<li>Indented item</li>
<li>Indented item</li>
</ul>
</li>
<li>Fourth item</li>
</ul>
  • First item
  • Second item
  • Third item
    • Indented item
    • Indented item
  • Fourth item

在列表中添加列表项

要在保留列表连续性的同时在列表中添加另一种元素,请将该元素缩进四个空格或一个制表符,如下例所示:

段落(Paragraphs)

*   This is the first list item.
*   Here's the second list item.

    I need to add another paragraph below the second list item.

*   And here's the third list item.

渲染效果如下:

  • This is the first list item.
  • Here’s the second list item.

    I need to add another paragraph below the second list item.

  • And here’s the third list item.

引用块(Blockquotes)

*   This is the first list item.
*   Here's the second list item.

    > A blockquote would look great below the second list item.

*   And here's the third list item.

渲染效果如下:

  • This is the first list item.
  • Here’s the second list item.

    A blockquote would look great below the second list item.

  • And here’s the third list item.

代码块(Code Blocks)

代码块(Code blocks) 通常采用四个空格或一个制表符缩进。当它们被放在列表中时,请将它们缩进八个空格或两个制表符。

1.  Open the file.
2.  Find the following code block on line 21:

        <html>
          <head>
            <title>Test</title>
          </head>

3.  Update the title to match the name of your website.

渲染效果如下:

  1. Open the file.
  2. Find the following code block on line 21:

    <html>
      <head>
        <title>Test</title>
      </head>
    
  3. Update the title to match the name of your website.

图像(Images)

1.  Open the file containing the Linux mascot.
2.  Marvel at its beauty.

    ![Tux, the Linux mascot](/assets/images/tux.png)

3.  Close the file.

渲染效果如下:

  1. Open the file containing the Linux mascot.
  2. Marvel at its beauty.

    Tux, the Linux mascot

  3. Close the file.

代码

要将单词或短语表示为代码,请将其包裹在反引号 (`) 中。

Markdown HTML 渲染效果
At the command prompt, type `nano`. At the command prompt, type <code>nano</code>. At the command prompt, type nano.

转义反引号

如果你要表示为代码的单词或短语中包含一个或多个反引号,则可以通过将单词或短语包裹在双反引号(``)中。

Markdown HTML 渲染效果
``Use `code` in your Markdown file.`` <code>Use `code` in your Markdown file.</code> Use `code` in your Markdown file.

代码块(Code Blocks)

要创建代码块,请将代码块的每一行缩进至少四个空格或一个制表符。

    <html>
      <head>
      </head>
    </html>

渲染效果如下:

<html>
  <head>
  </head>
</html>
注意: 要创建不用缩进的代码块,请使用 围栏式代码块(fenced code blocks).

分隔线(Horizontal Rules)

要创建分隔线,请在单独一行上使用三个或多个星号 (***)、破折号 (---) 或下划线 (___) ,并且不能包含其他内容。

***

---

_________________

以上三个分隔线的渲染效果看起来都一样:


分隔线(Horizontal Rule)用法最佳实践

为了兼容性,请在分隔线的前后均添加空白行。

✅  这样做 ❌  不要这样做
Try to put a blank line before...

---

...and after a horizontal rule.
Without blank lines, this would be a heading.
---
Don't do this!

To create a link, enclose the link text in brackets (e.g., [Duck Duck Go]) and then follow it immediately with the URL in parentheses (e.g., (https://duckduckgo.com)).

My favorite search engine is [Duck Duck Go](https://duckduckgo.com).

The rendered output looks like this:

My favorite search engine is Duck Duck Go.

Adding Titles

You can optionally add a title for a link. This will appear as a tooltip when the user hovers over the link. To add a title, enclose it in parentheses after the URL.

My favorite search engine is [Duck Duck Go](https://duckduckgo.com "The best search engine for privacy").

The rendered output looks like this:

My favorite search engine is Duck Duck Go.

URLs and Email Addresses

To quickly turn a URL or email address into a link, enclose it in angle brackets.

<https://www.markdownguide.org>
<fake@example.com>

The rendered output looks like this:

https://www.markdownguide.org
fake@example.com

To emphasize links, add asterisks before and after the brackets and parentheses. To denote links as code, add backticks in the brackets.

I love supporting the **[EFF](https://eff.org)**.
This is the *[Markdown Guide](https://www.markdownguide.org)*.
See the section on [`code`](#code).

The rendered output looks like this:

I love supporting the EFF.
This is the Markdown Guide.
See the section on code.

Reference-style links are a special kind of link that make URLs easier to display and read in Markdown. Reference-style links are constructed in two parts: the part you keep inline with your text and the part you store somewhere else in the file to keep the text easy to read.

The first part of a reference-style link is formatted with two sets of brackets. The first set of brackets surrounds the text that should appear linked. The second set of brackets displays a label used to point to the link you’re storing elsewhere in your document.

Although not required, you can include a space between the first and second set of brackets. The label in the second set of brackets is not case sensitive and can include letters, numbers, spaces, or punctuation.

This means the following example formats are roughly equivalent for the first part of the link:

  • [hobbit-hole][1]
  • [hobbit-hole] [1]

The second part of a reference-style link is formatted with the following attributes:

  1. The label, in brackets, followed immediately by a colon and at least one space (e.g., [label]: ).
  2. The URL for the link, which you can optionally enclose in angle brackets.
  3. The optional title for the link, which you can enclose in double quotes, single quotes, or parentheses.

This means the following example formats are all roughly equivalent for the second part of the link:

  • [1]: https://en.wikipedia.org/wiki/Hobbit#Lifestyle
  • [1]: https://en.wikipedia.org/wiki/Hobbit#Lifestyle "Hobbit lifestyles"
  • [1]: https://en.wikipedia.org/wiki/Hobbit#Lifestyle 'Hobbit lifestyles'
  • [1]: https://en.wikipedia.org/wiki/Hobbit#Lifestyle (Hobbit lifestyles)
  • [1]: <https://en.wikipedia.org/wiki/Hobbit#Lifestyle> "Hobbit lifestyles"
  • [1]: <https://en.wikipedia.org/wiki/Hobbit#Lifestyle> 'Hobbit lifestyles'
  • [1]: <https://en.wikipedia.org/wiki/Hobbit#Lifestyle> (Hobbit lifestyles)

You can place this second part of the link anywhere in your Markdown document. Some people place them immediately after the paragraph in which they appear while other people place them at the end of the document (like endnotes or footnotes).

An Example Putting the Parts Together

Say you add a URL as a standard URL link to a paragraph and it looks like this in Markdown:

In a hole in the ground there lived a hobbit. Not a nasty, dirty, wet hole, filled with the ends
of worms and an oozy smell, nor yet a dry, bare, sandy hole with nothing in it to sit down on or to
eat: it was a [hobbit-hole](https://en.wikipedia.org/wiki/Hobbit#Lifestyle "Hobbit lifestyles"), and that means comfort.

Though it may point to interesting additional information, the URL as displayed really doesn’t add much to the existing raw text other than making it harder to read. To fix that, you could format the URL like this instead:

In a hole in the ground there lived a hobbit. Not a nasty, dirty, wet hole, filled with the ends
of worms and an oozy smell, nor yet a dry, bare, sandy hole with nothing in it to sit down on or to
eat: it was a [hobbit-hole][1], and that means comfort.

[1]: <https://en.wikipedia.org/wiki/Hobbit#Lifestyle> "Hobbit lifestyles"

In both instances above, the rendered output would be identical:

In a hole in the ground there lived a hobbit. Not a nasty, dirty, wet hole, filled with the ends of worms and an oozy smell, nor yet a dry, bare, sandy hole with nothing in it to sit down on or to eat: it was a hobbit-hole, and that means comfort.

and the HTML for the link would be:

<a href="https://en.wikipedia.org/wiki/Hobbit#Lifestyle" title="Hobbit lifestyles">hobbit-hole</a>

Markdown applications don’t agree on how to handle spaces in the middle of a URL. For compatibility, try to URL encode any spaces with %20.

✅  Do this ❌  Don't do this
[link](https://www.example.com/my%20great%20page) [link](https://www.example.com/my great page)

Images

To add an image, add an exclamation mark (!), followed by alt text in brackets, and the path or URL to the image asset in parentheses. You can optionally add a title after the URL in the parentheses.

![Philadelphia's Magic Gardens. This place was so cool!](/assets/images/philly-magic-gardens.jpg "Philadelphia's Magic Gardens")

The rendered output looks like this:

Philadelphia's Magic Gardens. This place was so cool!

Linking Images

To add a link to an image, enclose the Markdown for the image in brackets, and then add the link in parentheses.

[![An old rock in the desert](/assets/images/shiprock.jpg "Shiprock, New Mexico by Beau Rogers")](https://www.flickr.com/photos/beaurogers/31833779864/in/photolist-Qv3rFw-34mt9F-a9Cmfy-5Ha3Zi-9msKdv-o3hgjr-hWpUte-4WMsJ1-KUQ8N-deshUb-vssBD-6CQci6-8AFCiD-zsJWT-nNfsgB-dPDwZJ-bn9JGn-5HtSXY-6CUhAL-a4UTXB-ugPum-KUPSo-fBLNm-6CUmpy-4WMsc9-8a7D3T-83KJev-6CQ2bK-nNusHJ-a78rQH-nw3NvT-7aq2qf-8wwBso-3nNceh-ugSKP-4mh4kh-bbeeqH-a7biME-q3PtTf-brFpgb-cg38zw-bXMZc-nJPELD-f58Lmo-bXMYG-bz8AAi-bxNtNT-bXMYi-bXMY6-bXMYv)

The rendered output looks like this:

An old rock in the desert

转义字符(Escaping Characters)

要显示原本用于格式化 Markdown 文档的字符,请在字符前面添加反斜杠字符 (\) 。

\* 如果没有开头的反斜杠字符的话,这一行将显示为无序列表。

渲染效果如下:

* 如果没有开头的反斜杠字符的话,这一行将显示为无序列表。

可做转义的(英文)字符

以下列出的字符都可以通过使用反斜杠字符从而达到转义目的。

字符 名称
\ 反斜杠(backslash)
` backtick (另请参见 在代码中转义反引号)
* 星号(asterisk)
_ 下划线(underscore)
{ } 花括号(curly braces)
[ ] 方括号(brackets)
( ) 圆括号或括号(parentheses)
# 井号(pound sign)
+ 加号(plus sign)
- 减号(minus sign) (也叫连字符 hyphen)
. 句点(dot)
! 感叹号(exclamation mark)
| 管道符(pipe) (另请参见 在表格中转义管道符)

HTML 标签

大多 Markdown 应用程序允许你在 Markdown 格式文本中添加 HTML 标签。如果你喜欢某些 HTML 标签胜于 Markdown 语法的话,这将何有帮助。例如,某些人发现通过 HTML 标签添加图像更加容易。当你需要更改元素的属性时(例如为文本指定颜色或更改图像的宽度),使用 HTML 标签更方便些。

如需使用 HTML,请将 HTML 标签添加到 Markdown 格式文本中即可。

This **word** is bold. This <em>word</em> is italic.

渲染效果如下:

This word is bold. This word is italic.

HTML 用法最佳实践

出于安全原因,并非所有 Markdown 应用程序都支持在 Markdown 文档中添加 HTML。如有疑问,请查看 Markdown 应用程序的文档。某些应用程序只支持 HTML 标签的子集。

对于 HTML 的块级元素 <div><table><pre><p>,请在其前后使用空行(blank lines)与其它内容进行分隔。尽量不要使用制表符(tabs)或空格(spaces)对 HTML 标签做缩进,否则将影响格式。

在 HTML 块级标签内不能使用 Markdown 语法。例如 <p>italic and **bold**</p> 将不起作用。