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HTML Validator

Find markup errors, warnings, and missing document essentials on any page.

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What Is HTML Validator?

The HTML Validator parses any page and reports markup errors and warnings with line numbers, plus checks for a doctype, language attribute, title, single H1, and image alt text. It catches the structural mistakes that break rendering, accessibility, and SEO.

Who Uses the HTML Validator?

Developers, QA testers, and accessibility auditors use it for pre-launch checks and for diagnosing pages that render oddly.

How to Use the HTML Validator

  1. Enter the full URL of the page to validate.
  2. Review the document checks: doctype, lang, title, H1, alt.
  3. Work through the parser errors and warnings by line.

Why Choose Our HTML Validator?

  • Parser errors and warnings with line numbers
  • Doctype, language, title, H1, and alt essentials checked
  • Plain-language findings, not raw parser dumps

Try the HTML Validator above — it is free, fast, and works on any device. Bookmark this page to return whenever you need it.