syntaxhighlight

Syntax highlighting is a feature of text editors, integrated development environments, and documentation tools that renders source code and other text with color and typographic styling to distinguish elements such as keywords, operators, strings, comments, and punctuation. The goal is to improve readability, help readers scan code more quickly, and reduce the likelihood of missing mistakes.

Most implementations work by tokenizing the input into a sequence of tokens and then applying a style map that associates token categories with colors or font attributes. Some systems support nested or embedded languages and can perform lightweight lexical highlighting or more sophisticated semantic highlighting that reflects types and bindings. Highlighting can run in the client (in the browser), on the server, or be pre-rendered into documents.

Common tools include Pygments (Python), Rouge (Ruby), highlight.js, Prism, and various language packs. Many code editors and IDEs—such as VS Code, Sublime Text, IntelliJ products, and Atom—include built-in syntax highlighting, often with extensive language support and theming. In web contexts, highlighted code is typically emitted as HTML with span elements carrying CSS classes, allowing easy theming through stylesheets.

Security and accessibility considerations include escaping highlighted HTML to avoid injection, selecting high-contrast color schemes, and offering non-visual cues or high-contrast themes for readers with color-vision deficiencies. Providing multiple themes and optional semantic highlighting can improve usefulness across workflows.