Markdown looks like one language until the same file renders differently on GitHub, Hugo, Obsidian, or Pandoc. And the problem is not that Markdown is unreliable.
It is that "Markdown" describes a family of related syntaxes, parsers, and platform features rather than a single universal document format. CommonMark defines a precise portable core, GitHub Flavored Markdown adds features useful for software collaboration, and Pandoc Markdown expands the language into a serious document-authoring format.
Choosing between them depends on where the document must render. A README file, a Hugo blog post, and an academic paper each have different requirements. This comparison is part of the broader documentation tooling picture and covers the formal dialects, platform-specific extensions, and practical portability rules so you can pick the right syntax for your target environment. For a quick syntax reference, the Markdown cheatsheet covers the essential formatting elements.
Markdown Is Not One Language
The original Markdown syntax was intentionally small and loosely specified. That made it easy to read and implement, but different parsers began interpreting ambiguous input differently.
