HTML Validator
Check your HTML code for syntax errors, unclosed tags, and common issues. Validate your markup in seconds.
Click "Validate HTML" to check your code
Validation Features
Tag Matching
Detects unclosed tags and mismatched opening/closing pairs.
Instant Results
Validate your HTML in milliseconds, right in the browser.
Best Practices
Warns about missing DOCTYPE, lang attribute, and alt text.
100% Free
No sign-up, no limits. Validate as much HTML as you need.
Perfect For
Frequently Asked Questions
How do I validate HTML online?
Paste your HTML code into the input area and click "Validate HTML". The tool will check for syntax errors and display the results with detailed error messages.
What errors does the validator check for?
The validator checks for unclosed tags, improperly nested elements, mismatched opening and closing tags, missing DOCTYPE, missing lang attribute, and missing alt text on images.
Why should I validate my HTML?
Valid HTML ensures your pages render correctly across all browsers, improves accessibility for screen readers, and can positively impact SEO rankings.
Is this the same as the W3C validator?
This is a lightweight syntax checker that runs in your browser. For full W3C specification compliance testing, use the official W3C Markup Validation Service.
Can I validate partial HTML snippets?
Yes. You can paste a full document or a partial snippet. The validator will check whatever code you provide for structural issues.
Is my code sent to a server?
No. All validation happens entirely in your browser. Your code never leaves your device.