HTML Formatter npm

This tool formats HTML by converting raw markup into a deterministic, readable layout. It accepts an HTML string from code, a file, or a CI artifact and outputs a single formatted string with standardized indentation, line breaks, and attribute wrapping. It supports HTML5 semantics, including void elements and boolean attributes, as well as common authoring patterns such as nested elements, multi-line attributes, and templates. It is designed for use in build pipelines, code editors, and code-review workflows that require repeatable markup conventions. Default settings use two-space indentation and conservative line-wrapping, with options to adjust indent_size, max_line_length, and attribute wrapping behavior.

Core logic parses the input into a DOM-like model and serializes it back with deterministic rules. It optionally reorders attributes, preserves or collapses comments, and can minify output when requested. Required inputs include the HTML string; optional inputs include indent_size (2–4), max_line_length (e.g., 80–120), wrap_attributes (true/false), and preserve_comments (true/false). Outputs include formatted_html (string) and diagnostics (array of messages) to aid troubleshooting. The formatter reports parse errors with location hints and does not mutate the original input until formatting completes.

Audience and value: front-end developers, CMS integrators, template authors, and tooling engineers gain faster code reviews, deterministic diffs, and easier integration into CI/CD pipelines. Unique differentiators include offline operation with no network calls, a deterministic formatting model, robust handling of edge cases (malformed markup, unusual attributes, preformatted blocks), and flexible options that support both strict and permissive styles. It functions as both a library and a command-line tool within Node.js environments, enabling reuse across projects without relying on external services.