HTML Validator & Linter

Find missing closing tags, broken nesting, and syntax errors in your HTML instantly.

HTML Source

Scanned 8 tags

<img> tag is missing the required "alt" attribute.

Mismatched closing tag </div>. Expected closing tag for <p> opened on line 4.

Common HTML Errors

Browsers are very forgiving, often hiding HTML mistakes that can break layouts or SEO. This tool catches:

Unclosed Tags: Forgetting </div> is the #1 cause of broken website layouts.
Mismatched Nesting: Illegal nesting like <b><i>...</b></i>.
Missing Attributes: Warnings for accessibility issues like missing alt tags on images or href on anchors.
Deprecated Tags: Alerts you if you are using old tags like <center> or <font> that are not supported in HTML5.

🐛

If your footer is floating in the middle of the page, you likely have a missing closing div.

🔍

Clean, semantic HTML helps search engine bots crawl and understand your content structure better.

♿

Valid HTML is the first step towards a WCAG-compliant website that works for screen readers.

Compare these examples to see how validation helps.

❌ Invalid HTML

<div class="card">
  <h1>Title
  <p>Paragraph with <b>bold</p></b>
  <img src="pic.jpg">
<!-- Missing closing div -->

✅ Valid HTML

<div class="card">
  <h1>Title</h1>
  <p>Paragraph with <b>bold</b></p>
  <img src="pic.jpg" alt="Description" />
</div>

Common reasons include missing closing tags, using deprecated tags (like <center>), or nesting block elements inside inline elements.

Yes. You don't need a full <html> document. You can paste a single <div> block to check if it's correct.

Yes, the validator is configured for modern HTML5 standards, including semantic tags like <main>, <article>, and <nav>.

Auto-format & beautify.

Check JSON syntax.

Encode special chars.