HTML Code Validator

A developer-focused HTML validation tool that analyzes input HTML, detects syntax and nesting errors, and produces actionable reports for code quality, QA, and education.

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100%

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4.9 / 5.0

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About This Tool

The HTML Code Validator ingests raw HTML and performs structural and syntax checks against the HTML5 specification. It identifies missing end tags, improper nesting, stray attributes, and invalid entities. It produces a structured report including error codes, line and column locations, and severity.
The tool uses an HTML5 tokenizer plus a rule-based validator to classify issues into errors and warnings, with actionable messages that point to precise locations in the source. It does not fetch remote resources and does not execute scripts, ensuring a safe, offline analysis.
Developers, QA engineers, educators, and content teams benefit from accurate, deterministic feedback that accelerates debugging, improves markup quality, and supports accessibility auditing. Unique value lies in consistent error taxonomy, exact location references, and a machine-friendly output suitable for integration into CI pipelines or educational demos.
Core features include parsing, tag balancing checks, attribute validation, nesting verification, and optional ARIA consistency checks. Use cases range from validating single HTML fragments to batch analysis of multiple files for code quality reviews.

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How to Use

Provide inputs by pasting your HTML code into the input field.
Choose doctype and parsing strictness to align with your project standards.
Run validation to generate a structured report of errors and warnings.
Review outputs with line/column references and suggested fixes.
Export results as JSON or human-readable summary for CI or documentation.

Frequently Asked Questions

Find Quick Answers

What HTML versions are supported?

The validator targets HTML5 semantics and common HTML5-era patterns. It can be extended to other profiles, but core checks focus on HTML5 as the baseline standard.

What outputs are produced?

The tool returns a boolean validity flag, a list of errors and warnings with location data, and a structured report that can be consumed by automation or shared with teammates.

Can results be exported?

Yes, results can be exported as JSON or a concise summary document. This facilitates integration into CI pipelines and documentation workflows.

How does it handle large HTML files?

It processes input in streaming-like fashion and enforces memory limits. For extremely large files, segment input or enable batch processing to stay within limits.

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