GitHub Flavored Markdown, often shortened as GFM, is the dialect of Markdown that is currently supported for user content on GitHub.com and GitHub Enterprise.

This formal specification, based on the CommonMark Spec, defines the syntax and semantics of this dialect.

GFM is a strict superset of CommonMark. All the features which are supported in GitHub user content and that are not specified on the original CommonMark Spec are hence known as extensions, and highlighted as such.