No. This is a practical linter focused on the most common real-world issues. The W3C Markup Validator performs exhaustive spec compliance checking and is the authoritative source for formal validation.
Free Developer Tool
HTML Validator, Auto-Fixer & Beautifier
Find unclosed and mismatched tags with exact line numbers, auto-repair broken markup structure, check for deprecated tags against your declared DOCTYPE, and beautify or minify — all in your browser.
- ✔ Line-numbered tag errors
- ✔ One-click auto-fix
- ✔ DOCTYPE-aware linting
- ✔ Beautify & minify
- ✔ Free Forever
Find and Fix Broken HTML Instantly
A missing closing tag can silently break page layout, cause content to render inside the wrong element, or make a page look fine in one browser and broken in another. This tool scans your HTML with a real tag-balance checker — pinpointing exactly which line has the unclosed or mismatched tag — while correctly ignoring tag-like text inside
<script>, <style>, comments, and
<textarea>, where false positives are most common.
It also checks for a missing DOCTYPE, flags tags and attributes deprecated in HTML5, catches duplicate IDs, and offers one-click auto-repair using the browser's own parser to rebuild valid structure — plus separate beautify and minify tools for formatting.
How It Works
1. Paste Your HTML
Any fragment or full document — select your DOCTYPE for accurate linting.
2. Review Issues
Every problem is listed with its exact line number and explanation.
3. Auto-Fix or Format
Repair structure automatically, or switch tabs to beautify or minify.
This is a practical structural linter, not a full W3C specification validator.
For authoritative, exhaustive spec compliance checking, also try the official
W3C Markup Validator.
Removes comments and collapses whitespace between tags, while preserving content
inside
<pre>, <script>, <style>,
and <textarea> exactly as written.
FAQsHTML Validator, Auto-Fixer & Beautifier
Is this the same as the official W3C validator?
How does Auto-Fix repair broken HTML?
It feeds your HTML through the browser's own built-in parser — the same forgiving parsing every browser already applies when rendering broken pages — then serializes the corrected structure back into clean text.
Why does the checker ignore tags inside my <script> block?
Text inside script, style, textarea, and comments is never parsed as markup by real browsers, even if it looks like a tag. This tool applies the same rule to avoid false positives.
Is my HTML uploaded anywhere?
No. Everything happens entirely in your browser. Nothing you paste is sent to any server.