HTML

HTML Validator

Find unclosed and mismatched HTML tags in seconds — with line numbers, not vague errors.

Validation runs locally in your browser. Nothing is uploaded, logged, or stored.

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Paste HTML to check tag balance and structure...

How to use

  1. Paste your HTML into the input panel.
  2. Click Validate — tags are checked against a balance stack as they are scanned.
  3. Review each issue with its line number, fix the markup, and validate again.

What does it check?

Every opening tag is pushed onto a stack and matched against its closing tag, so the validator catches tags that are never closed, closers that match the wrong element, and unexpected closers with no matching opener. Void elements like <img>, <br>, and <input> are treated correctly and never flagged as unclosed.

After fixing issues, prettify the result with the HTML Formatter. For strict well-formedness checks on XML, use the XML Validator.

Examples

Debug broken layouts

A single missing closing div can shift an entire page — locate it by line number in seconds.

Check hand-edited templates

Validate email or CMS templates after manual edits before they go live.

Frequently Asked Questions

Is my HTML uploaded anywhere?+
No. Validation happens entirely in your browser.
Is this a full W3C-style validator?+
No — it focuses on structural correctness (tag balance and nesting), which is where most real-world breakage comes from. It does not check attribute values or spec conformance.
Does it understand self-closing tags?+
Yes. Void elements and self-closing syntax like <img /> are handled without false positives.
Can I validate partial HTML?+
Yes — fragments are checked as-is; only imbalances within what you paste are reported.

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