Prism

Prism is a lightweight, robust, and elegant syntax highlighting library for the web. It tokenizes source code against grammar definitions and wraps each token in semantic markup, letting you style code with CSS themes rather than inline styles. Prism ships with definitions for hundreds of languages and a rich plugin ecosystem covering line numbers, copy-to-clipboard, autoloading, diff highlighting, and more.

Originally spun off from Lea Verou’s Dabblet, Prism runs in almost any browser and in Node.js. Its extensible, hook-based design lets you add languages, patch existing grammars, and hook into the highlighting lifecycle, which is why it powers documentation sites, blogs, and static site generators across the ecosystem.

What You Get

• A tiny core tokenizer with grammar definitions for 300+ programming languages
• A theme system driven entirely by CSS, with many bundled and community themes
• A plugin ecosystem: line numbers, copy-to-clipboard, autoloader, diff highlighting, and more
• First-class support for both browsers and Node.js via ESM and CommonJS builds
• TypeScript type definitions and an extensible, hook-based highlighting lifecycle

Common Use Cases

• Highlighting fenced code blocks on documentation sites and technical blogs
• Rendering syntax-highlighted snippets in static site generators at build time
• Displaying read-only code samples inside web apps and component libraries
• Adding language-aware highlighting to Markdown/MDX pipelines

Under The Hood

Architecture - Prism’s core (src/core/) is a small tokenizer: tokenize/tokenize.js walks source text against a grammar object of named regex patterns, producing a doubly linked-list.js token stream that stringify.js renders into nested <span> markup with token-type classes. A registry.js manages language components by id, resolving aliases and lazily loading grammars so hundreds of languages need not all be present. highlight.js, highlight-element.js, and highlight-all.js are the public entry points, with auto-start.js wiring up automatic highlighting of the page. A hook system lets plugins observe and mutate the highlighting lifecycle. Tech Stack - Pure JavaScript authored as ESM in src/, with a custom scripts/build.js producing both the ESM (dist/) and CommonJS (dist/cjs/) builds plus generated TypeScript declarations (types/). It has zero runtime dependencies, targets Node.js >=18, and uses ESLint and Prettier for consistency. Code Quality - The repo carries 27 Mocha test files under tests/ covering the core, individual language definitions, plugins, regex patterns, and identifiers, alongside tsc typechecking of both source and tests. Source is thoroughly JSDoc-annotated (the Registry class documents every field and method), and a dedicated SECURITY.md describes how the maintainers triage ReDoS reports inherent to a regex-based highlighter. API Design - The public surface is deliberately minimal and ergonomic: Prism.highlight(code, grammar, language) for strings, highlightElement/highlightAll for the DOM, and declarative grammar objects plus a hook API for extension. Language grammars can be patched or extended without forking, and the extensive prismjs.com documentation and examples/ folder keep the getting-started boilerplate near zero.