HTML Validator — Free Online
Catch unclosed tags, bad nesting and duplicate IDs. Works in your browser, no install needed.
Free with a CeevTech Tools account — no credit card required.
How to use HTML Validator
Paste your HTML into the box.
Click Validate.
Fix each issue using the line numbers in the report.
Why use CeevTech HTML Validator?
A missing closing tag can quietly break a page layout. CeevTech HTML Validator checks the HTML you paste for unclosed tags, stray or mismatched closing tags, duplicate IDs and unquoted attribute values, and reports each problem with its line number. It runs locally in your browser, so it is handy for checking snippets, email templates and pages before they go live.
- Fast: processes your URL or code in seconds.
- Private: runs in your browser, so nothing is uploaded.
- Works everywhere: desktop, tablet and phone, in any modern browser.
- One account, 79+ tools: PDF, image, office, AI, developer and business tools in one place.
Frequently asked questions
Is this the same as the W3C validator?
No. It is a structural check focused on tag nesting and closing, duplicate IDs and unquoted attributes. It does not check every rule in the HTML specification.
Will it flag tags like <img> or <br> as unclosed?
No. Void elements such as img, br, input, meta and link, and self-closing tags, are recognised and not expected to have a closing tag.
Is HTML Validator free?
Free with a CeevTech Tools account — no credit card required.
Do I need to install anything?
No. HTML Validator runs online in your browser on Windows, Mac, Linux, Android and iPhone.
Is my data private?
Yes. HTML Validator runs entirely in your browser, so your data never leaves your device.