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https://github.com/gomarkdown/markdown

markdown parser and HTML renderer for Go
https://github.com/gomarkdown/markdown

go golang markdown

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markdown parser and HTML renderer for Go

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# Markdown Parser and HTML Renderer for Go



[![pkg.go.dev](https://pkg.go.dev/badge/github.com/gomarkdown/markdown)](https://pkg.go.dev/github.com/gomarkdown/markdown)



Package `github.com/gomarkdown/markdown` is a Go library for parsing Markdown text and rendering as HTML.



It's very fast and supports common extensions.



Tutorial: https://blog.kowalczyk.info/article/cxn3/advanced-markdown-processing-in-go.html



Code examples:

* https://tools.arslexis.io/goplayground/#txO7hJ-ibeU : basic markdown => HTML

* https://tools.arslexis.io/goplayground/#yFRIWRiu-KL : customize HTML renderer

* https://tools.arslexis.io/goplayground/#2yV5-HDKBUV : modify AST

* https://tools.arslexis.io/goplayground/#9fqKwRbuJ04 : customize parser

* https://tools.arslexis.io/goplayground/#Bk0zTvrzUDR : syntax highlight



Those examples are also in [examples](./examples) directory.



## API Docs:



- https://pkg.go.dev/github.com/gomarkdown/markdown : top level package

- https://pkg.go.dev/github.com/gomarkdown/markdown/ast : defines abstract syntax tree of parsed markdown document

- https://pkg.go.dev/github.com/gomarkdown/markdown/parser : parser

- https://pkg.go.dev/github.com/gomarkdown/markdown/html : html renderer



## Usage



To convert markdown text to HTML using reasonable defaults:



```go

package main



import (

	"os"



	"github.com/gomarkdown/markdown"

	"github.com/gomarkdown/markdown/ast"

	"github.com/gomarkdown/markdown/html"

	"github.com/gomarkdown/markdown/parser"



	"fmt"

)



var mds = `# header



Sample text.



[link](http://example.com)

`



func mdToHTML(md []byte) []byte {

	// create markdown parser with extensions

	extensions := parser.CommonExtensions | parser.AutoHeadingIDs | parser.NoEmptyLineBeforeBlock

	p := parser.NewWithExtensions(extensions)

	doc := p.Parse(md)



	// create HTML renderer with extensions

	htmlFlags := html.CommonFlags | html.HrefTargetBlank

	opts := html.RendererOptions{Flags: htmlFlags}

	renderer := html.NewRenderer(opts)



	return markdown.Render(doc, renderer)

}



func main() {

	md := []byte(mds)

	html := mdToHTML(md)



	fmt.Printf("--- Markdown:\n%s\n\n--- HTML:\n%s\n", md, html)

}

```



Try it online: https://onlinetool.io/goplayground/#txO7hJ-ibeU



For more documentation read [this guide](https://blog.kowalczyk.info/article/cxn3/advanced-markdown-processing-in-go.html)



Comparing to other markdown parsers: https://babelmark.github.io/



## 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)

```



## mdtohtml command-line tool



https://github.com/gomarkdown/mdtohtml is a command-line markdown to html

converter built using this library.



You can also use it as an example of how to use the library.



You can install it with:



    go get -u github.com/gomarkdown/mdtohtml



To run: `mdtohtml input-file [output-file]`



## 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

  ```



  Table footers are supported as well and can be added with equal signs (`=`):



  ```

  Name    | Age

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

  Bob     | 27

  Alice   | 23

  ========|======

  Total   | 50

  ```



  A cell spanning multiple columns (colspan) is supported, just repeat the pipe symbol:



  ```

  Name    | Age

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

  Bob     ||

  Alice   | 23

  ========|======

  Total   | 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

  translates into line breaks in the output. This extension is off by default.



- **Non blocking space**. With this extension enabled spaces preceded by a backslash

  in the input translates non-blocking spaces 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 `4⁄5`, which renders as

  4⁄5.



- **MathJaX Support** is an additional feature which is supported by

  many markdown editor. It translates inline math equations quoted by `$`

  and displays math blocks quoted by `$$` into MathJax compatible format.

  Hyphens (`_`) won't break LaTeX render within a math element any more.



  ```

  $$

  \left[ \begin{array}{a} a^l_1 \\ ⋮ \\ a^l_{d_l} \end{array}\right]

  = \sigma(

   \left[ \begin{matrix}

   	w^l_{1,1} & ⋯  & w^l_{1,d_{l-1}} \\

   	⋮ & ⋱  & ⋮  \\

   	w^l_{d_l,1} & ⋯  & w^l_{d_l,d_{l-1}} \\

   \end{matrix}\right]  ·

   \left[ \begin{array}{x} a^{l-1}_1 \\ ⋮ \\ ⋮ \\ a^{l-1}_{d_{l-1}} \end{array}\right] +

   \left[ \begin{array}{b} b^l_1 \\ ⋮ \\ b^l_{d_l} \end{array}\right])

   $$

  ```



- **Ordered list start number**. With this extension enabled an ordered list will start with

  the number that was used to start it.



- **Super and subscript**. With this extension enabled sequences between ^ will indicate

  superscript and ~ will become a subscript. For example: H~2~O is a liquid, 2^10^ is 1024.



- **Block level attributes** allow setting attributes (ID, classes and key/value pairs) on block

  level elements. The attribute must be enclosed with braces and be put on a line before the

  element.



  ```

  {#id3 .myclass fontsize="tiny"}

  # Header 1

  ```



  Will convert into `
Header 1
`.



- **Mmark support**, see  for all new syntax elements this adds.



## Users



Some tools using this package: https://pkg.go.dev/github.com/gomarkdown/markdown?tab=importedby



## History



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



I refactored the 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)