While nearly all Markdown clients support the basic markdown syntax, there are some “official” extended syntaxes that are not as widely supported. These are, unfortunately, also things that applications have come up with their own non-standard ways to implement.

Things commonly added:

• Tables

  | Header | Second Header, much longer | Third Header |
  | :---        |    :----:   |          ---: |
  | Left-aligned text | Centered text! | Right-aligned text.  |
  | A3  | B3 | C3 |
  

• Fenced Code Blocks

  ```javascript
  let i = 0;
  

• Footnotes

  My footnoted word[^1].
  
  [^1]: Footnote for that.
  

• Highlights

  The ==highlighted phrase== is in double equals signs.
  

• Superscript/Subscript

  3^2 = 9
  H~2~O = water
  

• Em and En-dashes

  -- en dash
  --- em dash
  

• Strikethrough

  This is ~~lame~~ cool.
  

Extended Markdown Specs/support:

• Github-flavored Markdown
  • A strict superset of CommonMark
• Kramdown
• Showdown
• MultiMarkdown

Source

Extended Syntax | Markdown Guide

Comparison of features in various Markdown flavors

Related Notes

Markdown