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Free Online HTML Validator

Validate your HTML against W3C standards and best practices quickly and easily. Improve your web pages with our free online tool.

Why Use ToolNest's HTML Validator?

  • 100% Free - No hidden costs or subscriptions
  • No Registration Required - Validate HTML instantly
  • Privacy Focused - Your code is never stored on our servers
  • W3C Standards Compliant - Ensure your HTML meets industry standards
  • File Upload Support - Validate HTML files up to 2MB
  • Detailed Error Reporting - Get line numbers and specific error messages
  • Improves Web Accessibility - Helps create more inclusive websites

How to Use the HTML Validator

  1. Paste your HTML code into the input box or upload an HTML file
  2. Click the "Validate HTML" button
  3. Review the validation results
  4. If errors are found, locate and fix them in your original HTML
  5. Re-validate your HTML to ensure all issues are resolved

HTML Validation Tips

  • Always include a proper DOCTYPE declaration
  • Use lowercase for HTML tag names for better readability
  • Close all tags properly, or use self-closing tags where appropriate
  • Use quotation marks for attribute values
  • Ensure your HTML is properly nested
  • Use semantic HTML elements to improve SEO and accessibility
  • Regularly validate your HTML during development to catch errors early