A missing </div> can break a whole page layout, and it is hard to spot by eye. Paste your HTML and this checker lists every unclosed or mismatched tag with the line it was opened on, wrong nesting (like a <div> inside a <span>), duplicate ids, repeated attributes, images without alt text and missing page basics such as the doctype, language, title and viewport.
loading toolHow to use the html checker
- Paste your code into the box (or tap Try a sample).
- Read the list of problems: ✕ marks an error, ! a warning.
- Tap Show next to a problem to jump to that line, fix it, and watch the list update.
Good to know
- Fix the first error first: one unclosed tag often causes several messages after it.
- Every id must be unique on a page, or labels, links and scripts point at the wrong element.
- Use alt="" for purely decorative images so screen readers skip them.
Questions
Does it follow the real HTML rules?
Yes. It knows which tags never need closing (like <br> and <img>) and which end tags HTML lets you leave out (like </li> and </p>), so it only reports real problems, not style choices.
Can I check a Blogger or WordPress template?
Yes, paste the HTML part. Template tags such as <b:if> are read as normal tags, so make sure each one is closed too.
Is this the same as the W3C validator?
It catches the structural mistakes that break pages most often, instantly and privately. The W3C validator also checks every attribute value against the full specification, so use it as a final check for big projects.
Is my data private?
Yes. Everything happens inside your own browser: nothing you type or choose is uploaded to us or anyone else.
Is it free?
Completely free, with no sign-up, no watermark and no limit on how many times you use it. Light ads keep the site running.
