the anatomy
A document, opened.
Every panel on this page is this library compiled to JavaScript: the source on the left, the tree it is read into on the right, and what each block becomes. Pick a line, or a node, and the rest follows.
sourcefive blocks
tree
the whole document
as html
§02
What the extensions add.
The same block, read twice: once as GitHub reads it, once as plain CommonMark. The difference is the whole point of a flavor.
gfmdefault
commonmarkno extensions
§03
When each block settles.
A model writes a document a token at a time. A block settles once no later text can change it, which is when a following line has closed it. Drag the ruler: the source fills in, and the blocks it has settled are written below.