The importance of standardization
As previously mentioned. Gruber’s initial description of Markdown contained ambiguities and omissions, but the idea of Markdown was very popular. Soon, different platforms create thier own implementations of Markdown. Those implementations quickly diverged since there was no real standard to follow and they wanted to add features to meet there specific needs.
In 2014, a group of long-standing Markdown contributors formed a committee to create CommonMark, an unambiguous specification and test suite for Markdown. This was an attempt to standardize the language and make it more consistent across different platforms.
Today, CommonMark and GitHub-flavored Markdown (GFM) are the most widely used implementations of Markdown. GFM is a superset of CommonMark with a few additional features that are specific to GitHub. In most cases, platforms that support Markdown base their implementations on CommonMark and add popular features as extensions.
Extensions
While CommonMark does a good job of standardizing the language, it doesn’t cover every feature that you may want from a markup language. Some of the most popular extensions to CommonMark are:
- Tables
- Extra emphasis - strike through, subscript & superscript
- Special class attributes (HTML attributes)
- Definition lists and footnotes
- Task Lists (from GFM)
- Alpha and Roman numbers for ordered lists
- Media support for youtube, etc.
- Abbreviations
- Custom containers blocks
- Figures & Mathematics/Latex extensions
- Emoji support
- YAML Front Matter
The Microsoft Learn documentation platform uses the Markdig library to render Markdown. Markdig is a .NET library that implements CommonMark and several popular extensions. It also provides a framework to add more extensions.