Markdown is a lightweight markup language, originally created by John Gruber and Aaron Swartz, allowing people “to write using an easy-to-read, easy-to-write plain text format, then convert it to structurally valid XHTML (or HTML language takes many cues from existing conventions for marking up plain text in email.

Markdown is also a Perl script written by Gruber, “Markdown.pl”, which converts marked-up text input to valid, well-formed XHTML or HTML and replaces left-pointing angle brackets (<) and ampersands with their corresponding character entity references. It can be used as a standalone script, as a plugin for Blosxom or Movable Type, or as a text filter for BBEdit.

Markdown has since been re-implemented by others as a Perl module available on CPAN (Text::Markdown), and in a variety of other programming languages. It is distributed under a BSD-style license and is included with, or available as a plugin for, several content-management systems.

Stack Overflow uses Markdown.

This wiki entry was copied from Wikipedia.

Formatting using Markdown

Different Markdown dialects use slightly different formatting, but here are the general ideas:

You can use ** or __ to start and end bold text.

**Danger:** you need to prepare user inputs to avoid SQL injection.

You can use * or _ to start and end italic text.

_A Christmas Carol_ is a book written by Charles Dickens.

You can use backticks to format code text.

An `if` statement checks a condition, and runs code if it is true.

You can use ``` to format entire code blocks (like the one below)

Here is some code:

```
for (i = 0; i < 10; i++) {
    print "hi";
}
```

You can use > at the start of a line to insert a quote.

The specification says:
> You need to put x and y in brackets

Markdown dialects

A number of Markdown dialects are in widespread use, most of which add or enhance support for things like tables and links. Notable examples include

• github-flavored-markdown - GitHub Flavored Markdown (GFM)
• multimarkdown - MultiMarkdown
• Pandoc Extended Markdown

Babelmark may be used to compare the output generated by different implementations of Markdown.

Since 2014, you also have CommonMark, a strongly defined, highly compatible specification of Markdown (see "Standard Markdown is now Common Markdown").