Version 0.29-gfm (2019-04-06)
This formal specification is based on the CommonMark Spec by John MacFarlane and licensed under 

• 1. Introduction
  • 1.1 What is GitHub Flavored Markdown?
  • 1.2 What is Markdown?
  • 1.3 Why is a spec needed?
  • 1.4 About this document
• 2. Preliminaries
  • 2.1 Characters and lines
  • 2.2 Tabs
  • 2.3 Insecure characters
• 3. Blocks and inlines
  • 3.1 Precedence
  • 3.2 Container blocks and leaf blocks
• 4. Leaf blocks
  • 4.1 Thematic breaks
  • 4.2 ATX headings
  • 4.3 Setext headings
  • 4.4 Indented code blocks
  • 4.5 Fenced code blocks
  • 4.6 HTML blocks
  • 4.7 Link reference definitions
  • 4.8 Paragraphs
  • 4.9 Blank lines
  • 4.10 Tables (extension)
• 5. Container blocks
  • 5.1 Block quotes
  • 5.2 List items
  • 5.3 Task list items (extension)
  • 5.4 Lists
• 6. Inlines
  • 6.1 Backslash escapes
  • 6.2 Entity and numeric character references
  • 6.3 Code spans
  • 6.4 Emphasis and strong emphasis
  • 6.5 Strikethrough (extension)
  • 6.6 Links
  • 6.7 Images
  • 6.8 Autolinks
  • 6.9 Autolinks (extension)
  • 6.10 Raw HTML
  • 6.11 Disallowed Raw HTML (extension)
  • 6.12 Hard line breaks
  • 6.13 Soft line breaks
  • 6.14 Textual content
• Appendix: A parsing strategy
  • Overview
  • Phase 1: block structure
  • Phase 2: inline structure