Unclosed Div Tag Example: How Validation Catches It

About this tool

This page opens the HTML validator preloaded with one of the most common real-world markup mistakes: a `<div class="container">` that opens but is never closed before `</body>` appears. The validator catches this the moment the page loads and reports exactly where the structure breaks — not with a vague 'invalid HTML' message, but a precise mismatched-tag report naming the line the div was opened on.

This kind of bug is notoriously hard to spot by eye in a large template, because everything above the missing closing tag renders exactly as intended and the visual damage — content collapsing into the wrong container, styles bleeding across sections — often shows up much further down the page than the actual mistake. A tag-matching validator finds it in milliseconds by tracking every open tag on a stack and flagging the first one that never gets popped correctly.

Paste your own markup into the box below to run the same check against it, or edit this example — add the missing `</div>` back in — to see the result flip from invalid to valid.

Example. The fragment <div><p></div> fails on the closing div, because the checker still expects </p> from the p that was opened.

Limit. Void tags such as img, br, meta, and input need no close tag. The checker matches tag names and quote marks. It does not apply the HTML5 content model or require attributes such as alt.