HTML Element Validator

The HTML Element Validator analyzes markup to verify tag pairing, nesting correctness, and attribute usage across HTML documents. It supports HTML5 and XHTML modes, recognizes doctype variations, and flags deprecated tags or improper attribute values. By focusing on structure and semantics rather than generic syntax, it serves developers, QA engineers, educators, and web designers who review markup quality, enforce coding standards, or teach HTML fundamentals. The tool is designed for rapid feedback during development and for rigorous checks during code reviews, ensuring markup that renders consistently across browsers.
Conceptually, the validator tokenizes input, builds a tree representation of elements, and applies a rule set that enforces proper tag closure, valid attribute names, and appropriate nesting. It reports errors with precise locations and severity, along with suggested fixes. Optional features include mode selection (HTML5 versus XHTML), custom tag allowances, and ARIA attribute guidance to support accessibility considerations. The core differentiator is its combined focus on structure and constraints, providing both error diagnostics and constructive remediation advice suitable for real-world coding workflows.
Use cases span fast in-editor checks, pre-pull request validations, teaching exercises, and automated QA pipelines. Outputs include a structured error list, a summary score, and an option to export results as JSON or CSV. The tool does not perform external fetches; it operates on user-supplied markup only, preserving privacy and enabling offline use. It complements lint tools by addressing HTML element relationships and attributes, helping teams maintain clean, standards-compliant markup with clearer audit trails.