markdown/README.md

Markdown Parser and HTML Renderer for Go [![GoDoc](https://godoc.org/github.com/gomarkdown/markdown?status.svg)](https://godoc.org/github.com/gomarkdown/markdown) [![Build Status](https://travis-ci.org/gomarkdown/markdown.svg?branch=master)](https://travis-ci.org/gomarkdown/markdown)
===========

Package `github.com/gomarkdown/markdown` is a Go library for parsing [Markdown](https://daringfireball.net/projects/markdown/) documents and rendering them to HTML.

It's fast and supports common extensions.

## Installation

    go get -u github.com/gomarkdown/markdown

API Docs: https://godoc.org/github.com/gomarkdown/markdown

## Usage

To convert markdown text to HTML using reasonable defaults:

```go
md := []byte("## markdown document")
output := markdown.ToHTML(md, nil, nil)
```

To customize both parser and HTML renderer:

```go
import (
    "github.com/gomarkdown/markdown"
    "github.com/gomarkdown/markdown/html"
    "github.com/gomarkdown/markdown/parser"
)

extensions := html.CommonExtensions | html.AutoHeadingIDs
parser := parser.NewWithExensions(extensions)

htmlFlags := html.CommonFlags | html.HrefTargetBlank
opts := html.RendererOptions{Flags: htmlFlags}
renderer := html.NewRenderer(opts)

md := []byte("markdown text")
html := markdown.ToHTML(md, parser, renderer)
```

## Sanitize untrusted content

We don't protect against malicious content. When dealing with user-provided
markdown, run renderer HTML through HTML sanitizer such as [Bluemonday](https://github.com/microcosm-cc/bluemonday).

Here's an example of simple usage with Bluemonday:

```go
import (
    "github.com/microcosm-cc/bluemonday"
    "github.com/gomarkdown/markdown"
)

// ...
maybeUnsafeHTML := markdown.ToHTML(md, nil, nil)
html := bluemonday.UGCPolicy().SanitizeBytes(maybeUnsafeHTML)
```

## Customizing parser and renderer

Ways to customize parser:
* use custom extensions by creating parser with `parser.NewWithExtensions(extensions)`
* over-ride `parser.Parser.ReferenceOverride` function

You can also check out [cmd/mdhtml](https://github.com/gomarkdown/markdown/tree/master/cmd/mdtohtml) for more complete example of how to use it.

You can install it with:

    go get -u github.com/gomarkdown/markdown/cmd/mdtohtml

This is a simple command-line tool to convert markdown files to HTML.

## Features

*   **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 this package is
    more consistent and cleaner.

*   **Common extensions**, including table support, fenced code
    blocks, autolinks, strikethroughs, non-strict emphasis, etc.

*   **Safety**. Markdown 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/gomarkdown/markdown#sanitize-untrusted-content).

*   **Fast**. 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**. Only depends on standard library packages in Go.

*   **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. We let 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:

        ```go
        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**. We 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.

*   **Hard line breaks**. With this extension enabled newlines in the input
    translate into line breaks in the output. This extension is off by default.

*   **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>.


## Todo

*   port https://github.com/russross/blackfriday/issues/348
*   port [LaTeX output](https://github.com/Ambrevar/Blackfriday-LaTeX):
    renders output as LaTeX.
*   port https://github.com/shurcooL/github_flavored_markdown to markdown
*   port [markdownfmt](https://github.com/shurcooL/markdownfmt): like gofmt,
    but for markdown.
*   More unit testing
*   Improve unicode support. It does not understand all unicode
    rules (about what constitutes a letter, a punctuation symbol,
    etc.), so it may fail to detect word boundaries correctly in
    some instances. It is safe on all utf-8 input.

## History

markdown is a fork of v2 of https://github.com/russross/blackfriday that is:

* actively maintained (sadly in Feb 2018 blackfriday was inactive for 5 months with many bugs and pull requests accumulated)
* refactored API (split into ast/parser/html sub-packages)

Blackfriday itself was based on C implementation [sundown](https://github.com/vmg/sundown) which in turn was based on [libsoldout](http://fossil.instinctive.eu/libsoldout/home).

## License

[Simplified BSD License](LICENSE.txt)