PHP Markdown Extra and GitHub-flavored Markdown (GFM) introduced some widely used extensions to the CommonMark syntax. The following pages briefly recap the syntax for these elements and show their standard layout and alternative options.

All extensions are enabled in Hugo by default, but we can disable them separately. (See the configuration file markup.yaml for this site)

Some extensions have already been mentioned:

renders URLs in Markdown automatically into links — a quick and dirty way to reference URLs.
substitutes ASCII punctuation characters with typographic characters. The substitution of quotation marks is a topic on the quote page.