It should be possible to change the base font size. about markdown-javafx-renderer HOT 1 OPEN

It is not hardcoded in Java code, but in default stylesheet bundled with the component.

1 If you getStylesheet().add(yourCss), you should be able to override all styling.

2 You may also discard the original styling which gives you full styling control from all javafx styling mechanisms. in order of priority (see javafx.css.StyleOrigin):

         object: MarkdownView() {
            init {
               stylesheets.clear()
            }
         }

E.g., I apply my own stylesheet on window root, which has an unfortunate effect that the bundled stylesheet, which is pinned on the component, takes priority over mine. I solved this by copying all the styling from bundled stylesheets into my own (where I change all values anyway) and discarding the original styling.

3 markdownNode.setStyle("your css code") should work as well, because it has greatest priority (even greater than java code)

from markdown-javafx-renderer.