Gfm Markdown

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DocFX supports DocFX Flavored Markdown, aka DFM. It supports all GitHub Flavored Markdown syntax and compatible with CommonMark. Also, DFM adds new syntax to support additional functionalities, including cross reference and file inclusion.


Typora gives you a seamless experience as both a reader and a writer. It removes the preview window, mode switcher, syntax symbols of markdown source code, and all other unnecessary distractions. Instead, it provides a real live preview feature to help you concentrate on the content itself. Distractions Free Seamless Live Preview. Markdown is a formatting language that is created for the web. The purpose of markdown is to make life easy when we are writing on the internet. Over time there are many flavors of markdown created. But in this article, our focus will be mainly on Github Flavored Markdown (GFM). Github is based on CommonMark. There are a lot of additional.

The default markdown engine generated by docfx init has been switched to markdig engine, which is built on the top of markdig. Previous markdown engine dfm and dfm-latest will be kept for compatibiilty.

Yaml Header

Yaml header in DFM is considered as the metadata for the Markdown file. It will transform to yamlheader tag when processed.Yaml header MUST be the first thing in the file and MUST take the form of valid YAML set between triple-dashed lines. Here is a basic example:

Cross Reference

Cross reference allows you to link to another topic by using its unique identifier (called UID) instead of using its file path.

For conceptual Markdown files UID can be defined by adding a uid metadata in YAML header:

For reference topics, UIDs are auto generated from source code and can be found in generated YAML files.

You can use one of the following syntax to cross reference a topic with UID defined:

  1. Markdown link: [link_text](xref:uid_of_the_topic)
  2. Auto link: <xref:uid_of_the_topic>
  3. Shorthand form: @'uid_of_the_topic'

All will render to:

If link_text is not specified, DocFX will extract the title from the target topic and use it as the link text.

Do not use the @uid link in brackets (like this: (@uid)). DocFX cannot parse this link. The @uid link should be separated with white spaces. If you need to add a link in brackets, use [](xref:uid).


Hashtag in xref is always treated as separator between file name and anchor name. That means if you have # in UID, it hasto be encoded to %23.

Actually xref format follows URI standard so all reserved characters should be encoded.

For more information, see cross reference.

File Inclusion

DFM adds syntax to include other file parts into current file, the included file will also be considered as in DFM syntax.

There are two types of file inclusion: Inline and block, as similar to inline code span and block code.


YAML header is NOT supported when the file is an inclusion.


Inline file inclusion is in the following syntax, in which <title> stands for the title of the included file, and <filepath> stands for the file path of the included file. The file path can be either absolute or relative.<filepath> can be wrapped by ' or '.


For inline file inclusion, the file included will be considered as containing only inline tags, for example,### header inside the file will not transfer since <h3> is a block tag, while [a](b) will transform to<a href='b'>a</a> since <a> is an inline tag.Also, ending white spaces will be trimmed, considering ending white spaces in inline inclusion in most cases are typos.


Block file inclusion must be in a single line and with no prefix characters before the start [. Content inside the included file will transform using DFM syntax.

Section definition

User may need to define section. Mostly used for code table.Give an example below.

The above blockquote Markdown text will transform to section html as in the following:

Code Snippet

Allows you to insert code with code language specified. The content of specified code path will expand.

  • <language> can be made up of any number of character and '-'. However, the recommended value should follow Highlight.js language names and aliases.
  • <codepath> is the path relative to the file containing this markdown content in file system, which indicates the code snippet file that you want to expand.
  • <queryoption> and <queryoptionvalue> are used together to retrieve part of the code snippet file in the line range or tag name way. We have 2 query string options to represent these two ways:
query string using #query string using ?
1. line range#L{startlinenumber}-L{endlinenumber}?start={startlinenumber}&end={endlinenumber}
2. tagname#{tagname}?name={tagname}
3. multiple region rangeUnsupported?range={rangequerystring}
4. highlight linesUnsupported?highlight={rangequerystring}
5. dedentUnsupported?dedent={dedentlength}
  • In ? query string, the whole file will be included if none of the first three option is specified.
  • If dedent isn't specified, the maximum common indent will be trimmed automatically.
  • <title> can be omitted as it doesn't affect the DocFX markup result, but it can beautify the result of other Markdown engine, like GitHub Preview.

Code Snippet Sample

Tag Name Representation in Code Snippet Source File

DFM currently supports the following <language> values to be able to retrieve by tag name:

  • C family
    • Start with: // <{name}>
    • End with: // </{name}>
    • Languages:actionscript,arduino,assembly (alias: nasm),c (alias: cpp, c++, objective-c, obj-c, objc, objectivec),csharp (alias: cs),cshtml,cuda,d (alias: dlang),fsharp (alias: fs),go (alias: golang),java,javascript (alias: js, node),pascal,php,processing,rust,scala,smalltalk,swift,typescript (alias: ts)
    • File,.asm,.ino,.c,.cc,.cpp,.cs,,.cuh,.d,.fs,.fsi,.fsx,.go,.h,.hpp,.java,.js,.pas,.php,.pde,.rs,.scala,.st,.swift,.ts
  • Basic family
    • Start with: ' <{name}>
    • End with: ' </{name}>
    • Languages:vb,vbhtml,vbnet,vbscript
    • File extensions:.bas,.vb,.vba,.vbhtml,.vbs
  • Markup language family
    • Start with: <!-- <{name}> -->
    • End with: <!-- </{name}> -->
    • Languages:cshtml,html,vbhtml,wsdl,xml,xsl,xslt,xsd,xaml
    • File extensions:.asp,.aspx,.csdl,.cshtml,.edmx,.jsp,.vbhtml,.wsdl,.xaml,.xml,.xsd,.xsl,.xslt,.html
  • Sql family
    • Start with: -- <{name}>
    • End with: -- </{name}>
    • Languages:sql
    • File extensions:.sql
  • Script family
    • Start with: # <{name}>
    • End with: # </{name}>
    • Languages:perl,powershell (alias: posh),python,r,ruby (alias: ru),shell (alias: sh, bash)
    • File extensions:.bash,.pl,.ps1,.py,.r,.ru,.ruby,.sh
  • Special language
    • batchfile
      • Start with: rem <{name}>
      • End with: rem </{name}>
      • Languages:batchfile
      • File extensions:.bat.cmd
    • csharp
      • Start with: #region {name}
      • End with: #endregion
      • Languages:csharp (alias: cs)
      • File extensions:.cs.cshtml
    • erlang
      • Start with: % <{name}>
      • End with: % </{name}>
      • Languages:erlang
      • File extensions:.erl
    • haskell
      • Start with: -- <{name}>
      • End with: -- </{name}>
      • Languages:haskell
      • File extensions:.hs
    • matlab
      • Start with: % <{name}>
      • End with: % </{name}>
      • Languages:matlab
      • File extensions:.matlab
    • lisp
      • Start with: ; <{name}>
      • End with: ; </{name}>
      • Languages:lisp
      • File extensions:.lisp,.lsp
    • lua
      • Start with: -- <{name}>
      • End with: -- </{name}>
      • Languages:lua
      • File extensions:.lua
    • vb
      • Start with: #Region {name}
      • End with: #End Region
      • Languages:vb (alias: vbnet)
      • File extensions:.vb.vbhtml

If dev-lang is not specified, file extension will be used to determine the language.

Code Snippet for Jupyter Notebooks

Allows you to insert code from a code cell of a Jupyter Notebook. The source content in the specified code cell will expand.

Steps to use this:

  1. In your Jupyter Notebook, add metadata to the code cell you will reference:

  2. In your .md file, use name to identify the cell.

Code Snippet for Jupyter Notebooks Sample

For this Jupyter Notebook cell:

Use the markup:


to display the lines of code in the source part of the cell:

Note (Warning/Tip/Important)

Using specific syntax inside block quote to indicate the following content is Note.

The above content will be transformed to the following html:

Here are all the supported note types with the styling of the default theme applied:


This is a note which needs your attention, but it's not super important.


This is a note which needs your attention, but it's not super important.


This is a warning containing some important message.


This is a warning containing some important message.


This is a warning containing some important message.

Tabbed content


  • Start a tab by a special markdown title (any level).
    • Title content should be a markdown link.
    • Link target is #tab/{tabid} or #tab/{tabid}/{condition}
  • Continue by any other content.
  • End by a markdown hr.


The result will be:

Tab group 1:

Tab content-1-1.

Tab content-2-1.

Gfm Markdown Problems

Tab group 2:

Tab content-a-1.

Tab content-b-1.

Tab group 3:

Tab content-1-1.

Tab content-2-1.

Tab group 4:

Tab content-a-2.


Tab content-b-2.


Tab groups with a same set of id are linkable in one page.

In example, tab group 1, 3 have same id set: tabid-1, tabid-2, tab group 2, 4 have same id set: tabid-a, tabid-b.

So tab group 1, 3 are linked, tab group 2, 4 are linked.When tab tabid-1 in tab group 1 is clicked, tab tabid-1 in tab group 3 will be selected in same time.But tab group 2, 4 do not have any changed.


Condition is the tab id of other table groups.



Tab Group 1:

Tab Group 2:

Tab content-a for 1.

Tab content-a for 2.

Tab content-b for 1.

Tab content-b for 2.

When select tabid-1 in tab group 1, you can get content-a or content-b for 1 in group 2.
When select tabid-2 in tab group 1, you can get content-a or content-b for 2 in group 2.


Allows you to add videos to your topics.



Gfm Markdown Math

You must provide the embed uri of the video you wish to add to your topic.



Differences introduced by DFM syntax


DFM introduces more syntax to support more functionalities. When GFM does not support them, preview theMarkdown file inside GFM Preview can lead to different results.

YAML header

In GFM, YAML header must start at the very beginning of the Markdown file.In DFM, YAML header contains more powerful meanings. Refer to Yaml Header for details.

In GFM, it would be rendered as <hr>a: b<hr>.
In DFM, it would be rendered as a YAML header.

If you want to get <hr> in html in DFM, use:

Gfm Markdown Cheat

or change content to make it not in YAML format:

Text after block extension

Some block extension in DFM cannot be recognized in GFM.In GFM, it would be treated as a part of paragraph.Then, following content would be treated as a part of paragraph.

Gfm Markdown Parser

For example:

In GFM, it will be rendered as a paragraph with content [!NOTE] This is code. in blockquote.
In DFM, it will be rendered as a code in note.

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In the original Markdown spec, John Gruber describes Markdown as 'a text-to-HTML conversion tool for web writers.'It was designed to be easy to read and easy to write, and it certainly meets those requirements.Compare writing a bold link in HTML:

with Markdown:

The Markdown version has almost 1/3 fewer characters without losing any information.

This ability to generate HTML without writing HTML hasn't gone unnoticed.Since 2004, Markdown has continued to climb in popularity.The Google Trends data for 'markdown' shows impressive growth, especially since 2010:

Markdown tooling has also exploded since 2004, with Markdown parsers in many languages (e.g., Python-Markdown for Python; Marked, Showdown, and markdown-it for JavaScript).At the same time, developers wrote extensions to extend Markdown's original feature set, including an extension to represent HTML tables with Markdown's characteristic user-friendliness.

Markdown Tables

The syntax for describing tables in Markdown was popularized by GitHub in the The GitHub Flavored Markdown (GFM) Spec.The GFM spec describes tables in Markdown like this:

A table is an arrangement of data with rows and columns, consisting of a single header row, a delimiter row separating the header from the data, and zero or more data rows.

In other words--or in other Markdown--this is what a table looks like following the GFM table spec:

This table is formatted to be easy on the eyes, but not all Markdown tables are.Take a look at the formatting of this table, which is equally compliant but less readable:

This readability issue gets even worse when adding rich content into table data cells:

Composing and editing Markdown tables while keeping them readable is no picnic.Thank goodness there's Table to Markdown!