Find unclosed tags, wrong nesting and other common problems in your HTML, with line numbers.
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How to use HTML Validator
Paste your HTML.
Read the list of problems with line and column numbers.
Click Go to line to jump to each one.
About HTML Validator
Browsers are forgiving. They will render broken HTML and quietly fix it in their own way, which is exactly why mistakes survive for years. This validator reads your markup the strict way and lists what looks wrong.
It checks that tags are opened and closed in the right order, finds elements that were never closed, reports duplicate id attributes and warns about images without an alt attribute. It is a structure check, not a full implementation of the W3C validator, so it will not know every rule of the HTML specification.
Frequently asked questions
Is this the same as the W3C validator?
No. The W3C validator checks every rule of the HTML standard. This tool covers the mistakes that cause most real-world bugs: unclosed and mismatched tags, duplicate ids and missing alt text.
Why does it not complain about a missing closing p or li tag?
Some closing tags are optional in HTML, and the browser knows how to handle that. We flag elements that cannot be left open.
Are void elements like br and img handled?
Yes. Void elements never need a closing tag, whether you write them as br or br/.
Does it check scripts and styles?
Their content is skipped, so a less-than sign inside JavaScript is not mistaken for a tag.