As of
Est. 

Prism

Prism is a JavaScript library for syntax highlighting. It converts program code into colorful HTML.

VitePress v0.x provided a plugin that replaces Markdown-it's highlighter (highlight.js) with Prism. In VitePress v1.0 the highlighter was replaced with Shiki.

See the note on dark mode for VitePress for information on customizing stylesheets for Prism.