===========

Blackfriday is a [Markdown][1] processor implemented in [Go][2]. It

is paranoid about its input (so you can safely feed it user-supplied

data), it is fast, it supports common extensions (tables, smart

punctuation substitutions, etc.), and it is safe for all utf-8

(unicode) input.

HTML output is currently supported, along with Smartypants

extensions.

It started as a translation from C of [Sundown][3].

Installation

------------

Versions

--------

Currently maintained and recommended version of Blackfriday is `v2`. It's being

developed on its own branch: https://github.com/russross/blackfriday/tree/v2 and the

documentation is available at

https://godoc.org/gopkg.in/russross/blackfriday.v2.

but we highly recommend using package management tool like [dep][7] or

[Glide][8] and make use of semantic versioning. With package management you

should import `github.com/russross/blackfriday` and specify that you're using

version 2.0.0.

Version 2 offers a number of improvements over v1:

* Cleaned up API

* A separate call to [`Parse`][4], which produces an abstract syntax tree for

  the document

* Latest bug fixes

* Flexibility to easily add your own rendering extensions

Potential drawbacks:

* Our benchmarks show v2 to be slightly slower than v1. Currently in the

  ballpark of around 15%.

* API breakage. If you can't afford modifying your code to adhere to the new API

  and don't care too much about the new features, v2 is probably not for you.

* Several bug fixes are trailing behind and still need to be forward-ported to

  v2. See issue [#348](https://github.com/russross/blackfriday/issues/348) for

  tracking.

Usage

-----

For the most sensible markdown processing, it is as simple as getting your input

into a byte slice and calling:

```go

output := blackfriday.Run(input)

```

Your input will be parsed and the output rendered with a set of most popular

extensions enabled. If you want the most basic feature set, corresponding with

the bare Markdown specification, use:

```go

output := blackfriday.Run(input, blackfriday.WithNoExtensions())

```

### Sanitize untrusted content

Blackfriday itself does nothing to protect against malicious content. If you are

dealing with user-supplied markdown, we recommend running Blackfriday's output

through HTML sanitizer such as [Bluemonday][5].

Here's an example of simple usage of Blackfriday together with Bluemonday:

```go

import (

    "github.com/microcosm-cc/bluemonday"

)

// ...

unsafe := blackfriday.Run(input)

html := bluemonday.UGCPolicy().SanitizeBytes(unsafe)

```

If you want to customize the set of options, use `blackfriday.WithExtensions`,

`blackfriday.WithRenderer` and `blackfriday.WithRefOverride`.

You can also check out `blackfriday-tool` for a more complete example

of how to use it. Download and install it using:

    go get github.com/russross/blackfriday-tool

This is a simple command-line tool that allows you to process a

markdown file using a standalone program.  You can also browse the

source directly on github if you are just looking for some example

code:

* <http://github.com/russross/blackfriday-tool>

Note that if you have not already done so, installing

`blackfriday-tool` will be sufficient to download and install

blackfriday in addition to the tool itself. The tool binary will be

installed in `$GOPATH/bin`.  This is a statically-linked binary that

can be copied to wherever you need it without worrying about

dependencies and library versions.

Features

--------

All features of Sundown are supported, including:

*   **Compatibility**. The Markdown v1.0.3 test suite passes with

    the `--tidy` option.  Without `--tidy`, the differences are

    mostly in whitespace and entity escaping, where blackfriday is

    more consistent and cleaner.

*   **Common extensions**, including table support, fenced code

    blocks, autolinks, strikethroughs, non-strict emphasis, etc.

*   **Safety**. Blackfriday is paranoid when parsing, making it safe

    to feed untrusted user input without fear of bad things

    happening. The test suite stress tests this and there are no

    known inputs that make it crash.  If you find one, please let me

    know and send me the input that does it.

    NOTE: "safety" in this context means *runtime safety only*. In order to

    protect yourself against JavaScript injection in untrusted content, see

    [this example](https://github.com/russross/blackfriday#sanitize-untrusted-content).

*   **Fast processing**. It is fast enough to render on-demand in

    most web applications without having to cache the output.

*   **Thread safety**. You can run multiple parsers in different

    goroutines without ill effect. There is no dependence on global

    shared state.

*   **Minimal dependencies**. Blackfriday only depends on standard

    library packages in Go. The source code is pretty

    self-contained, so it is easy to add to any project, including

    Google App Engine projects.

*   **Standards compliant**. Output successfully validates using the

    W3C validation tool for HTML 4.01 and XHTML 1.0 Transitional.

Extensions

----------

In addition to the standard markdown syntax, this package

implements the following extensions:

*   **Intra-word emphasis supression**. The `_` character is

    commonly used inside words when discussing code, so having

    markdown interpret it as an emphasis command is usually the

    wrong thing. Blackfriday lets you treat all emphasis markers as

    normal characters when they occur inside a word.

*   **Tables**. Tables can be created by drawing them in the input

    using a simple syntax:

    ```

    Name    | Age

    --------|------

    Bob     | 27

    Alice   | 23

    ```

*   **Fenced code blocks**. In addition to the normal 4-space

    indentation to mark code blocks, you can explicitly mark them

    and supply a language (to make syntax highlighting simple). Just

    mark it like this:

        func getTrue() bool {

            return true

        }

        ```

    You can use 3 or more backticks to mark the beginning of the

    block, and the same number to mark the end of the block.

*   **Definition lists**. A simple definition list is made of a single-line

    term followed by a colon and the definition for that term.

        Cat

        : Fluffy animal everyone likes

        Internet

        : Vector of transmission for pictures of cats

    Terms must be separated from the previous definition by a blank line.

*   **Footnotes**. A marker in the text that will become a superscript number;

    a footnote definition that will be placed in a list of footnotes at the

    end of the document. A footnote looks like this:

        This is a footnote.[^1]

        [^1]: the footnote text.

*   **Autolinking**. Blackfriday can find URLs that have not been

    explicitly marked as links and turn them into links.

*   **Strikethrough**. Use two tildes (`~~`) to mark text that

    should be crossed out.

*   **Smart quotes**. Smartypants-style punctuation substitution is

    supported, turning normal double- and single-quote marks into

    curly quotes, etc.

*   **LaTeX-style dash parsing** is an additional option, where `--`

    is translated into `–`, and `---` is translated into

    `—`. This differs from most smartypants processors, which

    turn a single hyphen into an ndash and a double hyphen into an

    mdash.

*   **Smart fractions**, where anything that looks like a fraction

    is translated into suitable HTML (instead of just a few special

    cases like most smartypant processors). For example, `4/5`

    becomes `<sup>4</sup>&frasl;<sub>5</sub>`, which renders as

    <sup>4</sup>&frasl;<sub>5</sub>.

Other renderers

---------------

Blackfriday is structured to allow alternative rendering engines. Here

are a few of note:

*   [github_flavored_markdown](https://godoc.org/github.com/shurcooL/github_flavored_markdown):

    provides a GitHub Flavored Markdown renderer with fenced code block

    highlighting, clickable heading anchor links.

    It's not customizable, and its goal is to produce HTML output

    equivalent to the [GitHub Markdown API endpoint](https://developer.github.com/v3/markdown/#render-a-markdown-document-in-raw-mode),

    except the rendering is performed locally.

*   [markdownfmt](https://github.com/shurcooL/markdownfmt): like gofmt,

    but for markdown.

    renders output as LaTeX.

----

*   More unit testing

    rules (about what constitutes a letter, a punctuation symbol,

    etc.), so it may fail to detect word boundaries correctly in

License

-------

[Blackfriday is distributed under the Simplified BSD License](LICENSE.txt)

   [1]: https://daringfireball.net/projects/markdown/ "Markdown"

   [2]: https://golang.org/ "Go Language"

   [3]: https://github.com/vmg/sundown "Sundown"

   [4]: https://godoc.org/gopkg.in/russross/blackfriday.v2#Parse "Parse func"

   [5]: https://github.com/microcosm-cc/bluemonday "Bluemonday"

   [6]: https://labix.org/gopkg.in "gopkg.in"