HTML Tag Validator: Find the Unclosed Tag Before It Breaks the Layout
Most layout mysteries start with a tag that never closed. A stack-based check finds it in seconds.
What is the HTML Tag Validator?
A single unclosed tag can shift a whole page layout, and the fault is often far from the visible break. This validator walks through your markup with a simple stack, pairing each closing tag with the most recent open one and listing whatever is left over. Void elements such as line breaks and images are allowed to stand alone, so only real imbalances are reported.
How to use it
- Paste the HTML fragment you want to check.
- Click Validate Tags.
- Read each reported problem in order.
- Fix the first mismatch first, then validate again.
Worked example
Validating a fragment with one unclosed paragraph reports that paragraph as the problem.
What is wrong with <p>Hello?
The paragraph is never closed: there is an opening paragraph tag and no closing tag, so the validator reports the paragraph as unclosed.
Frequently asked questions
Does it check attributes or nesting rules?
No. It checks tag balance only, so a well-balanced but semantically odd page can still pass.
Why are br and img not flagged as unclosed?
They are void elements that never take a closing tag, so the validator lets them stand alone.