prism.js - Prism is a lightweight, extensible syntax highlighter, built with modern web standards in mind.
Shiki - A beautiful syntax highlighter based on TextMate grammar, accurate and powerful.
highlight.js - Highlight.js is a syntax highlighter written in JavaScript. It works in the browser as well as on the server.
Chroma (Syntax Highlighter) - Chroma takes source code and other structured text and converts it into syntax highlighted HTML, ANSI-coloured text, etc.
Torchlight.dev - Torchlight is a VS Code-compatible syntax highlighter that requires no JavaScript, supports every language, every VS Code theme, line highlighting, git diffing, and more.
Rainbow (Syntax Highlighting) - Simple syntax highlighting library written in JavaScript.