Example
1 issue(s) — unclosed <p>
HTML Tag Validator
Quickly check HTML for unclosed or mismatched tags instantly in your browser. Free online HTML tag validator — finds mismatched and missing closing tags.
Enter the values below, then press Calculate (or press Enter). The calculator updates your results instantly. Try different values to see how your inputs change the outcome.
- HTML to check — enter a value. A typical HTML to check would be <div><p>Hello</div>.
- Review your results — the key output is highlighted, with supporting figures below.
Loading calculator…
Results
Result
| Detail | Value |
|---|---|
| Issues (one per line) | |
| Issue count |
What is this calculator for?
Detect unclosed, mismatched, or out-of-order HTML tags in a fragment.
How to Use This Calculator
Enter the values below, then press Calculate (or press Enter). The calculator updates your results instantly. Try different values to see how your inputs change the outcome.
- HTML to check — enter a value. A typical HTML to check would be <div><p>Hello</div>.
- Review your results — the key output is highlighted, with supporting figures below.
What You'll Need
- HTML to check
- a value · required
About This Calculator
This validator scans your HTML and uses a stack to track open tags, reporting any that are never closed, closed in the wrong order, or closed with no opener.
Void elements (img, br, input, etc.) and self-closing tags are handled correctly. It checks tag balance only, not full W3C conformance.
Validation runs entirely in your browser.
Worked Examples
Frequently Asked Questions
Does a clean result mean valid HTML?
Not necessarily — this checks structural balance only. Attributes, nesting rules, and document structure still follow the HTML spec, which a fuller validator would confirm.
Are HTML comments handled?
Comments (<!– –>) are ignored, which is fine for tag balancing since they have no open/close tags that affect nesting.