DevUtilX

HTML Validator — Check Markup & Accessibility

Paste HTML markup and run quick validation checks for best practices, accessibility, and common issues.

Run validation to see issues, counts, and recommendations. The validator detects accessibility and common HTML problems like missing alt, duplicate id, inline event handlers, and more.

How to Use the HTML Validator

  1. Paste your HTML markup in the left editor.
  2. Click Validate to run quick checks for accessibility and common issues.
  3. Review the categorized issues (Errors, Warnings, Info) on the right panel.
  4. Copy or download the JSON report for CI or sharing with teammates.

What this validator checks

  • • Presence of DOCTYPE and lang on <html>.
  • • Missing or empty <title> tag.
  • • Images missing alt attributes (accessibility).
  • • Anchor target="_blank" missing rel security attributes.
  • • Duplicate IDs, inline event handlers, deprecated tags, and large inline scripts/styles.

⚠️ Important: This is a quick, client-side checker for common issues. For full standard compliance and spec-level validation, use the W3C Validator or server-side linters.

💡 Pro Tip: Use this tool to catch accessibility and common markup issues early in development. Keep formatted source for development and use validated/minified output for production workflows.

What is an HTML Validator?

An HTML Validator is a tool that checks your HyperText Markup Language (HTML) code for syntax errors and compliance with web standards. It helps you find issues like unclosed tags, improper nesting of elements, and the use of deprecated attributes. Ensuring your HTML is valid is a crucial step in web development.

Why Use Our HTML Validator?

  • Cross-Browser Compatibility: Valid HTML is more likely to be rendered consistently across different web browsers.
  • Accessibility: Proper HTML structure is essential for assistive technologies like screen readers to interpret your content correctly.
  • SEO: Search engines can better understand and index your content when it's well-structured and valid.
  • Debugging: It's often the first step in debugging layout and styling issues, as invalid HTML can cause unexpected rendering problems.

🚀 Explore More Free Developer Tools

Don’t stop here! Supercharge your workflow with our other powerful converters & formatters.

✨ HTML Formatter

Format HTML code with proper indentation and tag structure

⚡️ HTML Minifier

Minify HTML by removing unnecessary whitespace and comments

🚀 Markdown to HTML

Convert Markdown text to HTML

💡 New tools are added regularly — bookmark DevUtilsX and stay ahead!

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