No. Self-closing syntax works only on void elements — br, img, input, hr and the rest — where it is optional anyway. On any other element the trailing slash is ignored completely and the tag stays open, so everything after it ends up nested inside. It is an easy habit to carry over from JSX or XML, and this tool flags it explicitly because the resulting bug looks nothing like its cause.

HTML Beautifier

Q: Will formatting change how my page looks?

No, and considerable care goes into that. Whitespace is significant in HTML in two places: between inline elements, where a newline renders as a space, and inside pre and textarea, where it is rendered literally. So inline runs are kept on one line, long lines are wrapped only at whitespace that already existed, and pre and textarea contents are copied byte for byte. Attribute values are never rewritten either — only the spacing between attributes is normalised.

Q: How do I find an unclosed tag?

Paste the markup here and read the structure check. It walks the document with a tag stack and reports three distinct problems: a tag opened and never closed at all, a closing tag with no matching opener, and — most usefully — a tag that was still open when an enclosing element closed, which is the case that silently swallows content. Each one names the element and the line it started on.

Q: Why does my page render fine if the HTML is broken?

Because the HTML5 specification requires browsers to recover from errors rather than refuse to render. Every browser implements the same recovery algorithm, so an unclosed div gets closed for you at a defined point — it just may not be the point you intended. The result renders, but your CSS selectors, querySelector calls and DOM traversal are all operating on a tree that differs from the one you wrote.

Q: Why does it warn about duplicate IDs?

Because an ID must be unique in a document and browsers do not enforce it. getElementById returns only the first match, so a handler bound by ID attaches to one element while you expected another; anchor links reach only the first; and some framework code will behave unpredictably. It is a common result of rendering a template inside a loop, and it produces bugs that are very hard to spot by reading.

Q: Does this validate my HTML?

Partly, and it is worth being precise. It checks structure — tag balance, nesting, duplicate IDs — plus a couple of accessibility basics like missing alt attributes. It does not check conformance: whether an element is allowed in that parent, whether an attribute is valid for that element, or whether required attributes are present. For that, run the W3C Markup Validation Service as well. The two catch different things.

Reformat messy or minified HTML, and find the unclosed tags and duplicate IDs hiding in it.

Indent Void tags Wrap at

Your HTML

Formatted

Paste some HTML to format it.

What It Does

This tool reindents HTML and then does the part that actually saves time: it walks the document with a tag stack and tells you what is structurally broken — which tag was opened and never closed, which closing tag has no opener, which IDs are duplicated, and on which line each problem sits. Reformatting is commodity work that any editor does. Knowing that line 47 opened a div nobody ever closed is what you came for.

When to Use It

You have minified or generated HTML and need to read it.
A layout is collapsing and you suspect an unclosed tag somewhere above the broken part.
JavaScript is picking up the wrong element and you want to check for a duplicate ID.
You are reviewing markup from a CMS or an email template and need it in a consistent shape first.

Worked Examples

Minified markup, reindented

The everyday case. Note that the h1 stays on one line with its em — its content is entirely inline, and breaking it apart would be harder to read while changing nothing useful.

An unclosed div

The div is opened and never closed, so the </section> closes it early. The analysis names both elements and both line numbers — which is the difference between a two-minute fix and an afternoon of bisecting.

Duplicate IDs

Perfectly valid-looking HTML that browsers render without complaint. But getElementById only ever returns the first, which is why a click handler silently attaches to the wrong element.

JSX habits in HTML

In JSX <div /> closes itself. In HTML the slash is ignored entirely, so the div stays open and swallows everything after it. The analysis flags the self-closing syntax on a non-void element.

Common Mistakes

Assuming a browser rendering it means the markup is valid. Browsers implement an error-recovery algorithm precisely so broken HTML still displays something — they silently close your unclosed tags at whatever point their rules dictate. It looks fine until a CSS selector or a querySelector stops matching.
Writing <div /> and expecting it to close. Self-closing syntax only applies to void elements like br and img; on anything else the slash is ignored and the element stays open. It is the most common habit carried over from JSX and XML.
Reusing an ID. IDs must be unique in a document — getElementById returns only the first match, CSS #id styles apply to all of them, and an anchor link only ever reaches one. Duplicates usually appear when a template is looped.
Reformatting inside pre or textarea. Whitespace in those is rendered literally, so a beautifier that reindents their contents visibly changes the page. This tool reproduces them byte for byte.
Adding line breaks between inline elements. A newline between two spans renders as a space, so a formatter that splits them apart changes the text — the reason this tool keeps inline runs on one line and only wraps at whitespace that already existed.

Features

Reindents with 2 spaces

4 spaces or tabs

Keeps inline runs on one line so rendering never changes

Preserves pre and textarea content byte for byte

Leaves script and style contents untouched while reindenting the block

Unclosed

stray and implicitly-closed tag detection with line numbers

Duplicate ID detection

Self-closing-non-void and </br> warnings

Missing alt attribute warnings

Nesting depth with the deepest path

HTML or XHTML void tag style

Configurable wrap width

Runs entirely in your browser

How to Use

1. Paste your HTML into the left box; the formatted result appears on the right as you type. 2. Adjust indentation and wrap width if you have a house style. 3. Read the structure check below — errors are listed first, with line numbers. 4. Copy or download the result, or press 'Use as input' to keep working from the cleaned-up version.

Frequently Asked Questions

Will formatting change how my page looks?

How do I find an unclosed tag?

Why does my page render fine if the HTML is broken?

Does <div /> close the div?

Why does it warn about duplicate IDs?

Does this validate my HTML?

Embed this HTML Beautifier

Paste this snippet into your site to embed the tool.

<iframe src="https://webtoolworld.com/embed/html-formatter" style="width:100%;min-height:560px;border:0" loading="lazy" title="HTML Beautifier"></iframe>
<p style="font-size:12px;margin-top:6px"><a href="https://webtoolworld.com/html-formatter">HTML Beautifier</a> by WebToolWorld</p>

Everything runs in your browser — your markup is never uploaded or stored. This is a formatter and a structural checker, not a full HTML5 validator: it does not implement the browser's error-recovery tree construction, so it reports what you actually wrote rather than what a browser would silently turn it into. That is deliberate, and it is why it catches things a rendered page hides. Attribute values, script bodies and pre content are reproduced exactly; only whitespace between elements is changed. For formal conformance checking, use the W3C validator as well.