# HTML Validator & Structure Checker

Run quick, pragmatic structural checks on your HTML to catch the mistakes that break a page: unclosed tags, mismatched or badly nested elements, and missing required attributes. The checks run entirely in your browser, so your markup stays private. This is a fast sanity check, not full W3C conformance validation.

This tool runs entirely in the browser. Nothing is uploaded, and no account is needed.

## How to use it

1. **Paste or drop your HTML.** Paste your HTML into the editor, or drag and drop an .html file onto the page.
2. **Run the checks.** Click Check to scan locally for unclosed tags, broken nesting, and missing required attributes.
3. **Fix and re-check.** Jump to each flagged issue, correct it, and run the checks again until the markup is clean.

## Frequently asked questions

### Is the HTML validator free?

Yes, free to use as often as you like, with no sign-up and no limits.

### Is my HTML uploaded to check it?

No. Every check runs entirely in your browser. Nothing is sent to a server, so your markup never leaves your machine.

### What exactly does it check?

It runs pragmatic structural checks: unclosed or mismatched tags, elements that are nested incorrectly, and missing required attributes such as alt on images. It points you at the spot so you can fix it fast.

### Is this the same as the W3C validator?

No, and it does not claim to be. This is a quick local sanity check for the structural problems that most often break a page, not a full W3C conformance validation of every HTML spec rule. For a complete standards audit, run the official W3C validator as well.

### Why does it flag valid-looking HTML?

The most common triggers are a tag you forgot to close, two tags closed in the wrong order, or a self-closing element written incorrectly. The message names the element and where it is, so the fix is usually quick.

### My HTML is clean. How do I format or preview it?

Use the HTML Formatter to pretty-print and indent it, or the HTML Viewer to render it live in a safe sandbox and check how it looks.