HtmlFormatter

HtmlFormatter is a software component used to generate HTML markup from token streams to render syntax-highlighted text in web contexts. It is commonly employed by code highlighters and documentation tools to present source code or structured text with color, emphasis, and layout that mirrors the original formatting.

In typical implementations, an HtmlFormatter converts tokens produced by a lexer into HTML elements such as spans, each tagged with CSS classes or inline styles that reflect the token type. The formatter can wrap code in standard HTML containers like pre and code and may offer options to include a complete CSS stylesheet or rely on external styles. It often supports line numbering, line highlighting, and various options for wrapping and indentation. Some variants allow inline styles to avoid separate CSS files, while others can emit a full standalone HTML document.

A prominent example is HtmlFormatter in the Python Pygments library, where users may configure the style, enable line numbers, and choose whether the output includes a full HTML page or just the code fragment. This makes HtmlFormatter suitable for embedding in blogs, documentation generators, code tutorials, and interactive development environments.

Considerations when using HtmlFormatter include accessibility (ensuring sufficient color contrast and semantic HTML), performance on large code blocks, and the choice between CSS classes versus inline styles. The formatter’s configurability allows integration with existing themes and web assets, enabling consistent presentation across platforms.

See also: Syntax highlighting, CSS-based formatting, code rendering libraries.