ValidateHTML vs Nu HTML Checker
Both tools validate HTML for free. Here's an honest comparison of the official W3C validator and ValidateHTML to help you pick the right one.
| Feature | </> ValidateHTML | Nu HTML Checker |
|---|---|---|
| HTML Validation | ||
| URL Input (Validate by URL) | ||
| Error & Warning Reporting | ||
| Line & Column Error Position | ||
| Free, No Login Required | ||
| Paste HTML Input | ||
| File Upload Input | ||
| Quality Score (0-100) | ||
| Modern Dark UI | ||
| No Ads Covering the Interface | ||
| HTML Formatting / Beautify | ||
| HTML Minification | ||
| CSS Validation | ||
| JSON Validation & Formatting | ||
| XML Validation | ||
| Meta Tag Checker | ||
| Open Graph Checker | ||
| Accessibility Checker | ||
| Robots.txt Checker | ||
| Multi-Tool Suite (12 tools) | ||
| Official W3C Standard | ||
| Public API | ||
| Self-Hostable (Open Source) | ||
| SVG Validation |
When to Use Each
Use ValidateHTML when:
- You want a quality score to track your HTML health
- You validate more than just HTML (CSS, JSON, XML, meta tags)
- You want a modern, clean interface with dark mode
- You need HTML formatting and minification alongside validation
Use Nu HTML Checker when:
- You need the official W3C validation standard
- You want to validate SVG documents
- You need a public API for automated validation
- You want to self-host the validator on your own server
Our Honest Take
The Nu HTML Checker (also known as validator.w3.org/nu) is the official W3C validation tool. It's the gold standard for HTML conformance checking. If you need authoritative validation against the HTML specification — for compliance, documentation, or technical proof — the Nu checker is the reference tool.
That said, the Nu checker's interface hasn't been updated in years. It focuses purely on standards compliance and doesn't offer formatting, quality scoring, or additional web development tools. ValidateHTML provides a more modern experience with a broader toolkit: validate HTML, CSS, JSON, and XML, check meta tags and Open Graph data, run accessibility audits, and format or minify code — all from one place.
If you need the definitive W3C stamp of validation or a public API for automated checks, the Nu checker is the right choice. If you want a faster, more complete web development toolkit with a modern UI, ValidateHTML covers more of the day-to-day workflow.
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Free, instant, no login. Paste your HTML or enter a URL to validate in seconds.
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