HTML Validator

Validate HTML syntax and find errors

Input HTML
Validation Result
Click "Validate HTML" to check syntax

🔧 Related Tools

What is HTML Validation?

HTML validation checks your HTML code against the official standards to ensure it's correctly structured and error‑free. Valid HTML helps ensure consistent rendering across browsers, better accessibility, and improved SEO. Common errors include unclosed tags, missing attributes, and incorrect nesting.

This tool validates HTML syntax and provides detailed error messages when invalid. It helps you quickly fix issues before deploying your web pages.

All processing is done locally in your browser – your data never leaves your device.

How to Use

Step 1: Paste your HTML into the input area.
Step 2: Click "Validate HTML".
Step 3: If valid, you'll see a success message. If invalid, the tool shows the error message.
Step 4: Copy the result using the "Copy Result" button.

Use this tool to debug HTML before deploying your website.

Examples

Valid HTML:
<div><p>Hello</p></div>
Result: ✅ Valid HTML

Invalid HTML (unclosed tag):
<div><p>Hello</div>
Result: ❌ Unclosed tag <p>

Who Uses HTML Validators?

  • Web Developers – ensuring clean markup.
  • SEO Specialists – improving search rankings.
  • QA Engineers – testing web pages.
  • Content Editors – checking embedded HTML.
  • Email Marketers – validating HTML emails.

Pro Tips

  • Always include the DOCTYPE declaration for proper rendering.
  • Close all tags, especially for non‑void elements like <p> and <div>.
  • Use lowercase tag names and quoted attribute values for best compatibility.
  • Validate HTML after making changes to catch errors early.
  • The copy button helps you save error reports for debugging.

Frequently Asked Questions

What's the difference between HTML validator and browser?
Browsers try to fix errors automatically, which can hide problems. A validator shows the actual errors so you can fix them properly.
Does it validate HTML5?
Yes, the validator checks HTML5 syntax including new elements like <article>, <section>, and <nav>.
What about self-closing tags?
In HTML5, void elements like <br> and <img> don't need to be self‑closed, but the validator accepts both.
Can I validate large HTML files?
Yes, the tool can validate moderately sized files. Very large files may take a few seconds.
Is my data sent to a server?
No, all validation happens locally in your browser.
What about JavaScript inside HTML?
JavaScript is treated as content; the validator only checks HTML syntax, not JS syntax.
Does it validate CSS inline styles?
No, only HTML structure is validated. Use a CSS validator for styles.