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HTML Validator

Validate HTML tag pairings, nesting structure, attribute format, and check self-closing void elements.

Interactive Online Utility

HTML Validator runs 100% locally in your browser sandbox with zero network roundtrips. Load or paste your code directly into the workspace above to format, parse, validate, or generate your output instantly. 

<div class="card">
  <h3>Hello world</h3>
  <p>Standard HTML tags.</p>
  <img src="avatar.jpg" />
</div>
PRO TIP Local Client-Side Processing

Otuls runs 100% locally in your browser. Your data is processed in-memory and never transmitted over external network connections.

Technical Guide & Overview

HTML Validator is a dedicated developer utility designed to streamline common workflow tasks with zero installation, instant execution, and complete data privacy.

How It Works Under the Hood

The tool leverages modern browser standards (HTML5, WebAssembly, WebGL, and modern ECMAScript) to execute complex computations directly on your local device CPU and GPU without offloading processing to third-party cloud servers.

Authoritative Specifications & Primary Standards

Official specifications, RFCs, and authoritative open-source repositories for HTML Validator:

W3C Standard

The World Wide Web Consortium check tool for HTML, XHTML, and SVG conformance.

GitHub Repository

Popular open-source static analysis engine for HTML code linting.

Zero-Knowledge Client-Side Sandboxing

Privacy First: This tool operates completely inside your browser with zero remote logging or tracking.

Frequently Asked Questions

Q: What does HTML Validator check?

It parses your HTML block, tracks opened and closed elements via stack structures, and detects mismatched tag names or unclosed elements.