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1<h1>Markdown: Syntax</h1>
2<ul id="ProjectSubmenu">
3    <li><a href="/projects/markdown/" title="Markdown Project Page">Main</a></li>
4    <li><a href="/projects/markdown/basics" title="Markdown Basics">Basics</a></li>
5    <li><a class="selected" title="Markdown Syntax Documentation">Syntax</a></li>
6    <li><a href="/projects/markdown/license" title="Pricing and License Information">License</a></li>
7    <li><a href="/projects/markdown/dingus" title="Online Markdown Web Form">Dingus</a></li>
8</ul>
9
10<ul>
11<li><a href="#overview">Overview</a><ul>
12<li><a href="#philosophy">Philosophy</a></li>
13<li><a href="#html">Inline HTML</a></li>
14<li><a href="#autoescape">Automatic Escaping for Special Characters</a></li>
15</ul>
16</li>
17<li><a href="#block">Block Elements</a><ul>
18<li><a href="#p">Paragraphs and Line Breaks</a></li>
19<li><a href="#header">Headers</a></li>
20<li><a href="#blockquote">Blockquotes</a></li>
21<li><a href="#list">Lists</a></li>
22<li><a href="#precode">Code Blocks</a></li>
23<li><a href="#hr">Horizontal Rules</a></li>
24</ul>
25</li>
26<li><a href="#span">Span Elements</a><ul>
27<li><a href="#link">Links</a></li>
28<li><a href="#em">Emphasis</a></li>
29<li><a href="#code">Code</a></li>
30<li><a href="#img">Images</a></li>
31</ul>
32</li>
33<li><a href="#misc">Miscellaneous</a><ul>
34<li><a href="#backslash">Backslash Escapes</a></li>
35<li><a href="#autolink">Automatic Links</a></li>
36</ul>
37</li>
38</ul>
39<p><strong>Note:</strong> This document is itself written using Markdown; you
40can <a href="/projects/markdown/syntax.text">see the source for it by adding '.text' to the URL</a>.</p>
41<hr />
42<h2 id="overview">Overview</h2>
43
44<h3 id="philosophy">Philosophy</h3>
45
46<p>Markdown is intended to be as easy-to-read and easy-to-write as is feasible.</p>
47<p>Readability, however, is emphasized above all else. A Markdown-formatted
48document should be publishable as-is, as plain text, without looking
49like it's been marked up with tags or formatting instructions. While
50Markdown's syntax has been influenced by several existing text-to-HTML
51filters -- including <a href="http://docutils.sourceforge.net/mirror/setext.html">Setext</a>, <a href="http://www.aaronsw.com/2002/atx/">atx</a>, <a href="http://textism.com/tools/textile/">Textile</a>, <a href="http://docutils.sourceforge.net/rst.html">reStructuredText</a>,
52<a href="http://www.triptico.com/software/grutatxt.html">Grutatext</a>, and <a href="http://ettext.taint.org/doc/">EtText</a> -- the single biggest source of
53inspiration for Markdown's syntax is the format of plain text email.</p>
54<p>To this end, Markdown's syntax is comprised entirely of punctuation
55characters, which punctuation characters have been carefully chosen so
56as to look like what they mean. E.g., asterisks around a word actually
57look like *emphasis*. Markdown lists look like, well, lists. Even
58blockquotes look like quoted passages of text, assuming you've ever
59used email.</p>
60<h3 id="html">Inline HTML</h3>
61
62<p>Markdown's syntax is intended for one purpose: to be used as a
63format for <em>writing</em> for the web.</p>
64<p>Markdown is not a replacement for HTML, or even close to it. Its
65syntax is very small, corresponding only to a very small subset of
66HTML tags. The idea is <em>not</em> to create a syntax that makes it easier
67to insert HTML tags. In my opinion, HTML tags are already easy to
68insert. The idea for Markdown is to make it easy to read, write, and
69edit prose. HTML is a <em>publishing</em> format; Markdown is a <em>writing</em>
70format. Thus, Markdown's formatting syntax only addresses issues that
71can be conveyed in plain text.</p>
72<p>For any markup that is not covered by Markdown's syntax, you simply
73use HTML itself. There's no need to preface it or delimit it to
74indicate that you're switching from Markdown to HTML; you just use
75the tags.</p>
76<p>The only restrictions are that block-level HTML elements -- e.g. <code>&lt;div&gt;</code>,
77<code>&lt;table&gt;</code>, <code>&lt;pre&gt;</code>, <code>&lt;p&gt;</code>, etc. -- must be separated from surrounding
78content by blank lines, and the start and end tags of the block should
79not be indented with tabs or spaces. Markdown is smart enough not
80to add extra (unwanted) <code>&lt;p&gt;</code> tags around HTML block-level tags.</p>
81<p>For example, to add an HTML table to a Markdown article:</p>
82<pre><code>This is a regular paragraph.
83
84&lt;table&gt;
85    &lt;tr&gt;
86        &lt;td&gt;Foo&lt;/td&gt;
87    &lt;/tr&gt;
88&lt;/table&gt;
89
90This is another regular paragraph.
91</code></pre>
92<p>Note that Markdown formatting syntax is not processed within block-level
93HTML tags. E.g., you can't use Markdown-style <code>*emphasis*</code> inside an
94HTML block.</p>
95<p>Span-level HTML tags -- e.g. <code>&lt;span&gt;</code>, <code>&lt;cite&gt;</code>, or <code>&lt;del&gt;</code> -- can be
96used anywhere in a Markdown paragraph, list item, or header. If you
97want, you can even use HTML tags instead of Markdown formatting; e.g. if
98you'd prefer to use HTML <code>&lt;a&gt;</code> or <code>&lt;img&gt;</code> tags instead of Markdown's
99link or image syntax, go right ahead.</p>
100<p>Unlike block-level HTML tags, Markdown syntax <em>is</em> processed within
101span-level tags.</p>
102<h3 id="autoescape">Automatic Escaping for Special Characters</h3>
103
104<p>In HTML, there are two characters that demand special treatment: <code>&lt;</code>
105and <code>&amp;</code>. Left angle brackets are used to start tags; ampersands are
106used to denote HTML entities. If you want to use them as literal
107characters, you must escape them as entities, e.g. <code>&amp;lt;</code>, and
108<code>&amp;amp;</code>.</p>
109<p>Ampersands in particular are bedeviling for web writers. If you want to
110write about 'AT&amp;T', you need to write '<code>AT&amp;amp;T</code>'. You even need to
111escape ampersands within URLs. Thus, if you want to link to:</p>
112<pre><code>http://images.google.com/images?num=30&amp;q=larry+bird
113</code></pre>
114<p>you need to encode the URL as:</p>
115<pre><code>http://images.google.com/images?num=30&amp;amp;q=larry+bird
116</code></pre>
117<p>in your anchor tag <code>href</code> attribute. Needless to say, this is easy to
118forget, and is probably the single most common source of HTML validation
119errors in otherwise well-marked-up web sites.</p>
120<p>Markdown allows you to use these characters naturally, taking care of
121all the necessary escaping for you. If you use an ampersand as part of
122an HTML entity, it remains unchanged; otherwise it will be translated
123into <code>&amp;amp;</code>.</p>
124<p>So, if you want to include a copyright symbol in your article, you can write:</p>
125<pre><code>&amp;copy;
126</code></pre>
127<p>and Markdown will leave it alone. But if you write:</p>
128<pre><code>AT&amp;T
129</code></pre>
130<p>Markdown will translate it to:</p>
131<pre><code>AT&amp;amp;T
132</code></pre>
133<p>Similarly, because Markdown supports <a href="#html">inline HTML</a>, if you use
134angle brackets as delimiters for HTML tags, Markdown will treat them as
135such. But if you write:</p>
136<pre><code>4 &lt; 5
137</code></pre>
138<p>Markdown will translate it to:</p>
139<pre><code>4 &amp;lt; 5
140</code></pre>
141<p>However, inside Markdown code spans and blocks, angle brackets and
142ampersands are <em>always</em> encoded automatically. This makes it easy to use
143Markdown to write about HTML code. (As opposed to raw HTML, which is a
144terrible format for writing about HTML syntax, because every single <code>&lt;</code>
145and <code>&amp;</code> in your example code needs to be escaped.)</p>
146<hr />
147<h2 id="block">Block Elements</h2>
148
149<h3 id="p">Paragraphs and Line Breaks</h3>
150
151<p>A paragraph is simply one or more consecutive lines of text, separated
152by one or more blank lines. (A blank line is any line that looks like a
153blank line -- a line containing nothing but spaces or tabs is considered
154blank.) Normal paragraphs should not be intended with spaces or tabs.</p>
155<p>The implication of the "one or more consecutive lines of text" rule is
156that Markdown supports "hard-wrapped" text paragraphs. This differs
157significantly from most other text-to-HTML formatters (including Movable
158Type's "Convert Line Breaks" option) which translate every line break
159character in a paragraph into a <code>&lt;br /&gt;</code> tag.</p>
160<p>When you <em>do</em> want to insert a <code>&lt;br /&gt;</code> break tag using Markdown, you
161end a line with two or more spaces, then type return.</p>
162<p>Yes, this takes a tad more effort to create a <code>&lt;br /&gt;</code>, but a simplistic
163"every line break is a <code>&lt;br /&gt;</code>" rule wouldn't work for Markdown.
164Markdown's email-style <a href="#blockquote">blockquoting</a> and multi-paragraph <a href="#list">list items</a>
165work best -- and look better -- when you format them with hard breaks.</p>
166<h3 id="header">Headers</h3>
167
168<p>Markdown supports two styles of headers, <a href="http://docutils.sourceforge.net/mirror/setext.html">Setext</a> and <a href="http://www.aaronsw.com/2002/atx/">atx</a>.</p>
169<p>Setext-style headers are "underlined" using equal signs (for first-level
170headers) and dashes (for second-level headers). For example:</p>
171<pre><code>This is an H1
172=============
173
174This is an H2
175-------------
176</code></pre>
177<p>Any number of underlining <code>=</code>'s or <code>-</code>'s will work.</p>
178<p>Atx-style headers use 1-6 hash characters at the start of the line,
179corresponding to header levels 1-6. For example:</p>
180<pre><code># This is an H1
181
182## This is an H2
183
184###### This is an H6
185</code></pre>
186<p>Optionally, you may "close" atx-style headers. This is purely
187cosmetic -- you can use this if you think it looks better. The
188closing hashes don't even need to match the number of hashes
189used to open the header. (The number of opening hashes
190determines the header level.) :</p>
191<pre><code># This is an H1 #
192
193## This is an H2 ##
194
195### This is an H3 ######
196</code></pre>
197<h3 id="blockquote">Blockquotes</h3>
198
199<p>Markdown uses email-style <code>&gt;</code> characters for blockquoting. If you're
200familiar with quoting passages of text in an email message, then you
201know how to create a blockquote in Markdown. It looks best if you hard
202wrap the text and put a <code>&gt;</code> before every line:</p>
203<pre><code>&gt; This is a blockquote with two paragraphs. Lorem ipsum dolor sit amet,
204&gt; consectetuer adipiscing elit. Aliquam hendrerit mi posuere lectus.
205&gt; Vestibulum enim wisi, viverra nec, fringilla in, laoreet vitae, risus.
206&gt;
207&gt; Donec sit amet nisl. Aliquam semper ipsum sit amet velit. Suspendisse
208&gt; id sem consectetuer libero luctus adipiscing.
209</code></pre>
210<p>Markdown allows you to be lazy and only put the <code>&gt;</code> before the first
211line of a hard-wrapped paragraph:</p>
212<pre><code>&gt; This is a blockquote with two paragraphs. Lorem ipsum dolor sit amet,
213consectetuer adipiscing elit. Aliquam hendrerit mi posuere lectus.
214Vestibulum enim wisi, viverra nec, fringilla in, laoreet vitae, risus.
215
216&gt; Donec sit amet nisl. Aliquam semper ipsum sit amet velit. Suspendisse
217id sem consectetuer libero luctus adipiscing.
218</code></pre>
219<p>Blockquotes can be nested (i.e. a blockquote-in-a-blockquote) by
220adding additional levels of <code>&gt;</code>:</p>
221<pre><code>&gt; This is the first level of quoting.
222&gt;
223&gt; &gt; This is nested blockquote.
224&gt;
225&gt; Back to the first level.
226</code></pre>
227<p>Blockquotes can contain other Markdown elements, including headers, lists,
228and code blocks:</p>
229<pre><code>&gt; ## This is a header.
230&gt;
231&gt; 1.   This is the first list item.
232&gt; 2.   This is the second list item.
233&gt;
234&gt; Here's some example code:
235&gt;
236&gt;     return shell_exec("echo $input | $markdown_script");
237</code></pre>
238<p>Any decent text editor should make email-style quoting easy. For
239example, with BBEdit, you can make a selection and choose Increase
240Quote Level from the Text menu.</p>
241<h3 id="list">Lists</h3>
242
243<p>Markdown supports ordered (numbered) and unordered (bulleted) lists.</p>
244<p>Unordered lists use asterisks, pluses, and hyphens -- interchangably
245-- as list markers:</p>
246<pre><code>*   Red
247*   Green
248*   Blue
249</code></pre>
250<p>is equivalent to:</p>
251<pre><code>+   Red
252+   Green
253+   Blue
254</code></pre>
255<p>and:</p>
256<pre><code>-   Red
257-   Green
258-   Blue
259</code></pre>
260<p>Ordered lists use numbers followed by periods:</p>
261<pre><code>1.  Bird
2622.  McHale
2633.  Parish
264</code></pre>
265<p>It's important to note that the actual numbers you use to mark the
266list have no effect on the HTML output Markdown produces. The HTML
267Markdown produces from the above list is:</p>
268<pre><code>&lt;ol&gt;
269&lt;li&gt;Bird&lt;/li&gt;
270&lt;li&gt;McHale&lt;/li&gt;
271&lt;li&gt;Parish&lt;/li&gt;
272&lt;/ol&gt;
273</code></pre>
274<p>If you instead wrote the list in Markdown like this:</p>
275<pre><code>1.  Bird
2761.  McHale
2771.  Parish
278</code></pre>
279<p>or even:</p>
280<pre><code>3. Bird
2811. McHale
2828. Parish
283</code></pre>
284<p>you'd get the exact same HTML output. The point is, if you want to,
285you can use ordinal numbers in your ordered Markdown lists, so that
286the numbers in your source match the numbers in your published HTML.
287But if you want to be lazy, you don't have to.</p>
288<p>If you do use lazy list numbering, however, you should still start the
289list with the number 1. At some point in the future, Markdown may support
290starting ordered lists at an arbitrary number.</p>
291<p>List markers typically start at the left margin, but may be indented by
292up to three spaces. List markers must be followed by one or more spaces
293or a tab.</p>
294<p>To make lists look nice, you can wrap items with hanging indents:</p>
295<pre><code>*   Lorem ipsum dolor sit amet, consectetuer adipiscing elit.
296    Aliquam hendrerit mi posuere lectus. Vestibulum enim wisi,
297    viverra nec, fringilla in, laoreet vitae, risus.
298*   Donec sit amet nisl. Aliquam semper ipsum sit amet velit.
299    Suspendisse id sem consectetuer libero luctus adipiscing.
300</code></pre>
301<p>But if you want to be lazy, you don't have to:</p>
302<pre><code>*   Lorem ipsum dolor sit amet, consectetuer adipiscing elit.
303Aliquam hendrerit mi posuere lectus. Vestibulum enim wisi,
304viverra nec, fringilla in, laoreet vitae, risus.
305*   Donec sit amet nisl. Aliquam semper ipsum sit amet velit.
306Suspendisse id sem consectetuer libero luctus adipiscing.
307</code></pre>
308<p>If list items are separated by blank lines, Markdown will wrap the
309items in <code>&lt;p&gt;</code> tags in the HTML output. For example, this input:</p>
310<pre><code>*   Bird
311*   Magic
312</code></pre>
313<p>will turn into:</p>
314<pre><code>&lt;ul&gt;
315&lt;li&gt;Bird&lt;/li&gt;
316&lt;li&gt;Magic&lt;/li&gt;
317&lt;/ul&gt;
318</code></pre>
319<p>But this:</p>
320<pre><code>*   Bird
321
322*   Magic
323</code></pre>
324<p>will turn into:</p>
325<pre><code>&lt;ul&gt;
326&lt;li&gt;&lt;p&gt;Bird&lt;/p&gt;&lt;/li&gt;
327&lt;li&gt;&lt;p&gt;Magic&lt;/p&gt;&lt;/li&gt;
328&lt;/ul&gt;
329</code></pre>
330<p>List items may consist of multiple paragraphs. Each subsequent
331paragraph in a list item must be intended by either 4 spaces
332or one tab:</p>
333<pre><code>1.  This is a list item with two paragraphs. Lorem ipsum dolor
334    sit amet, consectetuer adipiscing elit. Aliquam hendrerit
335    mi posuere lectus.
336
337    Vestibulum enim wisi, viverra nec, fringilla in, laoreet
338    vitae, risus. Donec sit amet nisl. Aliquam semper ipsum
339    sit amet velit.
340
3412.  Suspendisse id sem consectetuer libero luctus adipiscing.
342</code></pre>
343<p>It looks nice if you indent every line of the subsequent
344paragraphs, but here again, Markdown will allow you to be
345lazy:</p>
346<pre><code>*   This is a list item with two paragraphs.
347
348    This is the second paragraph in the list item. You're
349only required to indent the first line. Lorem ipsum dolor
350sit amet, consectetuer adipiscing elit.
351
352*   Another item in the same list.
353</code></pre>
354<p>To put a blockquote within a list item, the blockquote's <code>&gt;</code>
355delimiters need to be indented:</p>
356<pre><code>*   A list item with a blockquote:
357
358    &gt; This is a blockquote
359    &gt; inside a list item.
360</code></pre>
361<p>To put a code block within a list item, the code block needs
362to be indented <em>twice</em> -- 8 spaces or two tabs:</p>
363<pre><code>*   A list item with a code block:
364
365        &lt;code goes here&gt;
366</code></pre>
367<p>It's worth noting that it's possible to trigger an ordered list by
368accident, by writing something like this:</p>
369<pre><code>1986. What a great season.
370</code></pre>
371<p>In other words, a <em>number-period-space</em> sequence at the beginning of a
372line. To avoid this, you can backslash-escape the period:</p>
373<pre><code>1986\. What a great season.
374</code></pre>
375<h3 id="precode">Code Blocks</h3>
376
377<p>Pre-formatted code blocks are used for writing about programming or
378markup source code. Rather than forming normal paragraphs, the lines
379of a code block are interpreted literally. Markdown wraps a code block
380in both <code>&lt;pre&gt;</code> and <code>&lt;code&gt;</code> tags.</p>
381<p>To produce a code block in Markdown, simply indent every line of the
382block by at least 4 spaces or 1 tab. For example, given this input:</p>
383<pre><code>This is a normal paragraph:
384
385    This is a code block.
386</code></pre>
387<p>Markdown will generate:</p>
388<pre><code>&lt;p&gt;This is a normal paragraph:&lt;/p&gt;
389
390&lt;pre&gt;&lt;code&gt;This is a code block.
391&lt;/code&gt;&lt;/pre&gt;
392</code></pre>
393<p>One level of indentation -- 4 spaces or 1 tab -- is removed from each
394line of the code block. For example, this:</p>
395<pre><code>Here is an example of AppleScript:
396
397    tell application "Foo"
398        beep
399    end tell
400</code></pre>
401<p>will turn into:</p>
402<pre><code>&lt;p&gt;Here is an example of AppleScript:&lt;/p&gt;
403
404&lt;pre&gt;&lt;code&gt;tell application "Foo"
405    beep
406end tell
407&lt;/code&gt;&lt;/pre&gt;
408</code></pre>
409<p>A code block continues until it reaches a line that is not indented
410(or the end of the article).</p>
411<p>Within a code block, ampersands (<code>&amp;</code>) and angle brackets (<code>&lt;</code> and <code>&gt;</code>)
412are automatically converted into HTML entities. This makes it very
413easy to include example HTML source code using Markdown -- just paste
414it and indent it, and Markdown will handle the hassle of encoding the
415ampersands and angle brackets. For example, this:</p>
416<pre><code>    &lt;div class="footer"&gt;
417        &amp;copy; 2004 Foo Corporation
418    &lt;/div&gt;
419</code></pre>
420<p>will turn into:</p>
421<pre><code>&lt;pre&gt;&lt;code&gt;&amp;lt;div class="footer"&amp;gt;
422    &amp;amp;copy; 2004 Foo Corporation
423&amp;lt;/div&amp;gt;
424&lt;/code&gt;&lt;/pre&gt;
425</code></pre>
426<p>Regular Markdown syntax is not processed within code blocks. E.g.,
427asterisks are just literal asterisks within a code block. This means
428it's also easy to use Markdown to write about Markdown's own syntax.</p>
429<h3 id="hr">Horizontal Rules</h3>
430
431<p>You can produce a horizontal rule tag (<code>&lt;hr /&gt;</code>) by placing three or
432more hyphens, asterisks, or underscores on a line by themselves. If you
433wish, you may use spaces between the hyphens or asterisks. Each of the
434following lines will produce a horizontal rule:</p>
435<pre><code>* * *
436
437***
438
439*****
440
441- - -
442
443---------------------------------------
444
445_ _ _
446</code></pre>
447<hr />
448<h2 id="span">Span Elements</h2>
449
450<h3 id="link">Links</h3>
451
452<p>Markdown supports two style of links: <em>inline</em> and <em>reference</em>.</p>
453<p>In both styles, the link text is delimited by [square brackets].</p>
454<p>To create an inline link, use a set of regular parentheses immediately
455after the link text's closing square bracket. Inside the parentheses,
456put the URL where you want the link to point, along with an <em>optional</em>
457title for the link, surrounded in quotes. For example:</p>
458<pre><code>This is [an example](http://example.com/ "Title") inline link.
459
460[This link](http://example.net/) has no title attribute.
461</code></pre>
462<p>Will produce:</p>
463<pre><code>&lt;p&gt;This is &lt;a href="http://example.com/" title="Title"&gt;
464an example&lt;/a&gt; inline link.&lt;/p&gt;
465
466&lt;p&gt;&lt;a href="http://example.net/"&gt;This link&lt;/a&gt; has no
467title attribute.&lt;/p&gt;
468</code></pre>
469<p>If you're referring to a local resource on the same server, you can
470use relative paths:</p>
471<pre><code>See my [About](/about/) page for details.
472</code></pre>
473<p>Reference-style links use a second set of square brackets, inside
474which you place a label of your choosing to identify the link:</p>
475<pre><code>This is [an example][id] reference-style link.
476</code></pre>
477<p>You can optionally use a space to separate the sets of brackets:</p>
478<pre><code>This is [an example] [id] reference-style link.
479</code></pre>
480<p>Then, anywhere in the document, you define your link label like this,
481on a line by itself:</p>
482<pre><code>[id]: http://example.com/  "Optional Title Here"
483</code></pre>
484<p>That is:</p>
485<ul>
486<li>Square brackets containing the link identifier (optionally
487indented from the left margin using up to three spaces);</li>
488<li>followed by a colon;</li>
489<li>followed by one or more spaces (or tabs);</li>
490<li>followed by the URL for the link;</li>
491<li>optionally followed by a title attribute for the link, enclosed
492in double or single quotes.</li>
493</ul>
494<p>The link URL may, optionally, be surrounded by angle brackets:</p>
495<pre><code>[id]: &lt;http://example.com/&gt;  "Optional Title Here"
496</code></pre>
497<p>You can put the title attribute on the next line and use extra spaces
498or tabs for padding, which tends to look better with longer URLs:</p>
499<pre><code>[id]: http://example.com/longish/path/to/resource/here
500    "Optional Title Here"
501</code></pre>
502<p>Link definitions are only used for creating links during Markdown
503processing, and are stripped from your document in the HTML output.</p>
504<p>Link definition names may constist of letters, numbers, spaces, and punctuation -- but they are <em>not</em> case sensitive. E.g. these two links:</p>
505<pre><code>[link text][a]
506[link text][A]
507</code></pre>
508<p>are equivalent.</p>
509<p>The <em>implicit link name</em> shortcut allows you to omit the name of the
510link, in which case the link text itself is used as the name.
511Just use an empty set of square brackets -- e.g., to link the word
512"Google" to the google.com web site, you could simply write:</p>
513<pre><code>[Google][]
514</code></pre>
515<p>And then define the link:</p>
516<pre><code>[Google]: http://google.com/
517</code></pre>
518<p>Because link names may contain spaces, this shortcut even works for
519multiple words in the link text:</p>
520<pre><code>Visit [Daring Fireball][] for more information.
521</code></pre>
522<p>And then define the link:</p>
523<pre><code>[Daring Fireball]: http://daringfireball.net/
524</code></pre>
525<p>Link definitions can be placed anywhere in your Markdown document. I
526tend to put them immediately after each paragraph in which they're
527used, but if you want, you can put them all at the end of your
528document, sort of like footnotes.</p>
529<p>Here's an example of reference links in action:</p>
530<pre><code>I get 10 times more traffic from [Google] [1] than from
531[Yahoo] [2] or [MSN] [3].
532
533  [1]: http://google.com/        "Google"
534  [2]: http://search.yahoo.com/  "Yahoo Search"
535  [3]: http://search.msn.com/    "MSN Search"
536</code></pre>
537<p>Using the implicit link name shortcut, you could instead write:</p>
538<pre><code>I get 10 times more traffic from [Google][] than from
539[Yahoo][] or [MSN][].
540
541  [google]: http://google.com/        "Google"
542  [yahoo]:  http://search.yahoo.com/  "Yahoo Search"
543  [msn]:    http://search.msn.com/    "MSN Search"
544</code></pre>
545<p>Both of the above examples will produce the following HTML output:</p>
546<pre><code>&lt;p&gt;I get 10 times more traffic from &lt;a href="http://google.com/"
547title="Google"&gt;Google&lt;/a&gt; than from
548&lt;a href="http://search.yahoo.com/" title="Yahoo Search"&gt;Yahoo&lt;/a&gt;
549or &lt;a href="http://search.msn.com/" title="MSN Search"&gt;MSN&lt;/a&gt;.&lt;/p&gt;
550</code></pre>
551<p>For comparison, here is the same paragraph written using
552Markdown's inline link style:</p>
553<pre><code>I get 10 times more traffic from [Google](http://google.com/ "Google")
554than from [Yahoo](http://search.yahoo.com/ "Yahoo Search") or
555[MSN](http://search.msn.com/ "MSN Search").
556</code></pre>
557<p>The point of reference-style links is not that they're easier to
558write. The point is that with reference-style links, your document
559source is vastly more readable. Compare the above examples: using
560reference-style links, the paragraph itself is only 81 characters
561long; with inline-style links, it's 176 characters; and as raw HTML,
562it's 234 characters. In the raw HTML, there's more markup than there
563is text.</p>
564<p>With Markdown's reference-style links, a source document much more
565closely resembles the final output, as rendered in a browser. By
566allowing you to move the markup-related metadata out of the paragraph,
567you can add links without interrupting the narrative flow of your
568prose.</p>
569<h3 id="em">Emphasis</h3>
570
571<p>Markdown treats asterisks (<code>*</code>) and underscores (<code>_</code>) as indicators of
572emphasis. Text wrapped with one <code>*</code> or <code>_</code> will be wrapped with an
573HTML <code>&lt;em&gt;</code> tag; double <code>*</code>'s or <code>_</code>'s will be wrapped with an HTML
574<code>&lt;strong&gt;</code> tag. E.g., this input:</p>
575<pre><code>*single asterisks*
576
577_single underscores_
578
579**double asterisks**
580
581__double underscores__
582</code></pre>
583<p>will produce:</p>
584<pre><code>&lt;em&gt;single asterisks&lt;/em&gt;
585
586&lt;em&gt;single underscores&lt;/em&gt;
587
588&lt;strong&gt;double asterisks&lt;/strong&gt;
589
590&lt;strong&gt;double underscores&lt;/strong&gt;
591</code></pre>
592<p>You can use whichever style you prefer; the lone restriction is that
593the same character must be used to open and close an emphasis span.</p>
594<p>Emphasis can be used in the middle of a word:</p>
595<pre><code>un*fucking*believable
596</code></pre>
597<p>But if you surround an <code>*</code> or <code>_</code> with spaces, it'll be treated as a
598literal asterisk or underscore.</p>
599<p>To produce a literal asterisk or underscore at a position where it
600would otherwise be used as an emphasis delimiter, you can backslash
601escape it:</p>
602<pre><code>\*this text is surrounded by literal asterisks\*
603</code></pre>
604<h3 id="code">Code</h3>
605
606<p>To indicate a span of code, wrap it with backtick quotes (<code>`</code>).
607Unlike a pre-formatted code block, a code span indicates code within a
608normal paragraph. For example:</p>
609<pre><code>Use the `printf()` function.
610</code></pre>
611<p>will produce:</p>
612<pre><code>&lt;p&gt;Use the &lt;code&gt;printf()&lt;/code&gt; function.&lt;/p&gt;
613</code></pre>
614<p>To include a literal backtick character within a code span, you can use
615multiple backticks as the opening and closing delimiters:</p>
616<pre><code>``There is a literal backtick (`) here.``
617</code></pre>
618<p>which will produce this:</p>
619<pre><code>&lt;p&gt;&lt;code&gt;There is a literal backtick (`) here.&lt;/code&gt;&lt;/p&gt;
620</code></pre>
621<p>The backtick delimiters surrounding a code span may include spaces --
622one after the opening, one before the closing. This allows you to place
623literal backtick characters at the beginning or end of a code span:</p>
624<pre><code>A single backtick in a code span: `` ` ``
625
626A backtick-delimited string in a code span: `` `foo` ``
627</code></pre>
628<p>will produce:</p>
629<pre><code>&lt;p&gt;A single backtick in a code span: &lt;code&gt;`&lt;/code&gt;&lt;/p&gt;
630
631&lt;p&gt;A backtick-delimited string in a code span: &lt;code&gt;`foo`&lt;/code&gt;&lt;/p&gt;
632</code></pre>
633<p>With a code span, ampersands and angle brackets are encoded as HTML
634entities automatically, which makes it easy to include example HTML
635tags. Markdown will turn this:</p>
636<pre><code>Please don't use any `&lt;blink&gt;` tags.
637</code></pre>
638<p>into:</p>
639<pre><code>&lt;p&gt;Please don't use any &lt;code&gt;&amp;lt;blink&amp;gt;&lt;/code&gt; tags.&lt;/p&gt;
640</code></pre>
641<p>You can write this:</p>
642<pre><code>`&amp;#8212;` is the decimal-encoded equivalent of `&amp;mdash;`.
643</code></pre>
644<p>to produce:</p>
645<pre><code>&lt;p&gt;&lt;code&gt;&amp;amp;#8212;&lt;/code&gt; is the decimal-encoded
646equivalent of &lt;code&gt;&amp;amp;mdash;&lt;/code&gt;.&lt;/p&gt;
647</code></pre>
648<h3 id="img">Images</h3>
649
650<p>Admittedly, it's fairly difficult to devise a "natural" syntax for
651placing images into a plain text document format.</p>
652<p>Markdown uses an image syntax that is intended to resemble the syntax
653for links, allowing for two styles: <em>inline</em> and <em>reference</em>.</p>
654<p>Inline image syntax looks like this:</p>
655<pre><code>![Alt text](/path/to/img.jpg)
656
657![Alt text](/path/to/img.jpg "Optional title")
658</code></pre>
659<p>That is:</p>
660<ul>
661<li>An exclamation mark: <code>!</code>;</li>
662<li>followed by a set of square brackets, containing the <code>alt</code>
663attribute text for the image;</li>
664<li>followed by a set of parentheses, containing the URL or path to
665the image, and an optional <code>title</code> attribute enclosed in double
666or single quotes.</li>
667</ul>
668<p>Reference-style image syntax looks like this:</p>
669<pre><code>![Alt text][id]
670</code></pre>
671<p>Where "id" is the name of a defined image reference. Image references
672are defined using syntax identical to link references:</p>
673<pre><code>[id]: url/to/image  "Optional title attribute"
674</code></pre>
675<p>As of this writing, Markdown has no syntax for specifying the
676dimensions of an image; if this is important to you, you can simply
677use regular HTML <code>&lt;img&gt;</code> tags.</p>
678<hr />
679<h2 id="misc">Miscellaneous</h2>
680
681<h3 id="autolink">Automatic Links</h3>
682
683<p>Markdown supports a shortcut style for creating "automatic" links for URLs and email addresses: simply surround the URL or email address with angle brackets. What this means is that if you want to show the actual text of a URL or email address, and also have it be a clickable link, you can do this:</p>
684<pre><code>&lt;http://example.com/&gt;
685</code></pre>
686<p>Markdown will turn this into:</p>
687<pre><code>&lt;a href="http://example.com/"&gt;http://example.com/&lt;/a&gt;
688</code></pre>
689<p>Automatic links for email addresses work similarly, except that
690Markdown will also perform a bit of randomized decimal and hex
691entity-encoding to help obscure your address from address-harvesting
692spambots. For example, Markdown will turn this:</p>
693<pre><code>&lt;address@example.com&gt;
694</code></pre>
695<p>into something like this:</p>
696<pre><code>&lt;a href="&amp;#x6D;&amp;#x61;i&amp;#x6C;&amp;#x74;&amp;#x6F;:&amp;#x61;&amp;#x64;&amp;#x64;&amp;#x72;&amp;#x65;
697&amp;#115;&amp;#115;&amp;#64;&amp;#101;&amp;#120;&amp;#x61;&amp;#109;&amp;#x70;&amp;#x6C;e&amp;#x2E;&amp;#99;&amp;#111;
698&amp;#109;"&gt;&amp;#x61;&amp;#x64;&amp;#x64;&amp;#x72;&amp;#x65;&amp;#115;&amp;#115;&amp;#64;&amp;#101;&amp;#120;&amp;#x61;
699&amp;#109;&amp;#x70;&amp;#x6C;e&amp;#x2E;&amp;#99;&amp;#111;&amp;#109;&lt;/a&gt;
700</code></pre>
701<p>which will render in a browser as a clickable link to "address@example.com".</p>
702<p>(This sort of entity-encoding trick will indeed fool many, if not
703most, address-harvesting bots, but it definitely won't fool all of
704them. It's better than nothing, but an address published in this way
705will probably eventually start receiving spam.)</p>
706<h3 id="backslash">Backslash Escapes</h3>
707
708<p>Markdown allows you to use backslash escapes to generate literal
709characters which would otherwise have special meaning in Markdown's
710formatting syntax. For example, if you wanted to surround a word with
711literal asterisks (instead of an HTML <code>&lt;em&gt;</code> tag), you can backslashes
712before the asterisks, like this:</p>
713<pre><code>\*literal asterisks\*
714</code></pre>
715<p>Markdown provides backslash escapes for the following characters:</p>
716<pre><code>\   backslash
717`   backtick
718*   asterisk
719_   underscore
720{}  curly braces
721[]  square brackets
722()  parentheses
723#   hash mark
724+   plus sign
725-   minus sign (hyphen)
726.   dot
727!   exclamation mark
728</code></pre>