HTML5 Validator
Validate your webpage or raw HTML code against HTML5 standards using the W3C validator.
About This Tool
The HTML5 Validator tool checks your webpage or HTML code for HTML5 errors, warnings, and invalid markup. Clean, valid HTML improves accessibility, cross-browser rendering, SEO crawlability, and reduces layout/JS issues caused by broken tags.
Use it to validate:
Full page URL (live HTML source)
Raw HTML code (paste)
Specific template sections (header, footer, forms, landing pages)
How It Works
Input
You enter a webpage URL or paste HTML code.Fetch / Read HTML
If URL: the tool loads the page HTML (server-side)
If code: it uses your pasted markup directly
Validation Rules
It checks for common HTML5 issues like:
Unclosed or mismatched tags
Duplicate IDs
Invalid nesting (e.g., block inside inline incorrectly)
Missing required attributes
Deprecated elements/attributes
Invalid ARIA usage (optional, if included)
Results + Line References
It returns a clear report:
Errors (must fix)
Warnings (recommended)
Notes (best practice suggestions)
Often with line/column hints to locate the issue fast.
Still Have Questions?
Valid HTML helps pages render correctly across browsers, improves accessibility, and prevents hidden layout bugs that can hurt user experience and SEO.
No—this tool detects and reports issues. You fix them in your theme/template/page builder code using the provided hints.
Yes. It validates the final HTML output of the page. If issues come from plugins/widgets, you’ll see them in the report and can adjust the widget settings or custom code.
Browsers often “auto-correct” broken HTML, so pages can look fine but still contain invalid markup. Warnings help you prevent future issues and keep code clean.