CommonMark is a small, portable core. It does not include tables, task lists or footnotes1. GitHub Flavored Markdown specifies tables and task lists as extensions, and its spec does not define footnotes either2.
| Feature | CommonMark | GitHub Flavored Markdown |
|---|---|---|
| Tables | Not in the spec | Specified, as an extension |
| Task lists | Not in the spec | Specified, as an extension |
| Footnotes | Not in the spec | Not in the spec |
What will survive the move
- Tables written in GFM syntax are portable to tools that implement the GFM spec. A strict CommonMark renderer does not guarantee them12
- Task lists may render as plain list text on a strict CommonMark renderer12
- Footnotes are not portable by spec alone. GitHub renders them as a feature of its site, outside the GFM spec2

Watch it work