rehype

Rehype is a JavaScript tool in the unified ecosystem that enables processing HTML through a plugin-based pipeline. It reads HTML into a Hypertext Abstract Syntax Tree (HAST), applies a series of plugins to transform that tree, and then serializes the result back to HTML. Rehype is designed to work alongside remark, which handles Markdown, allowing developers to build end-to-end content pipelines that originate from Markdown or HTML and end in HTML.

At the core, rehype uses a processor that runs plugins in sequence. Typical components include rehype-parse, which parses HTML into HAST, and rehype-stringify, which converts HAST back into HTML. Individual plugins visit nodes in the HAST and produce a new tree, enabling tasks such as sanitization, attribute rewriting, minification, or accessibility improvements. The HAST format represents elements with type, tagName, properties, and children; text and comment nodes are represented accordingly.

Common use cases include sanitizing user input, adding anchors to headings, removing disallowed tags, optimizing markup, or injecting metadata. Rehype is frequently used in static site generators, content pipelines, and build tooling, and its plugin ecosystem supports a wide range of transformations and analyses.

As part of the unified project, rehype emphasizes a consistent, declarative approach to HTML processing. Its ecosystem encourages composing small, focused plugins to build complex transformations while maintaining readability and testability.