HTML Validator
Validate HTML markup for errors and warnings.
About HTML Validator
HTML Validator checks your markup against the HTML5 specification and reports errors (broken structure) and warnings (deprecated features or accessibility concerns). Fixing these issues leads to more consistent rendering across browsers and better accessibility scores. It is a good practice to validate before deploying any new page or component.
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Frequently Asked Questions
Is HTML Validator free?
Yes, completely free. No signup, no account, no usage limits. Use it as much as you need.
Is my data secure?
All processing happens directly in your browser using JavaScript. Your data is never sent to any server, stored, or shared. It stays entirely on your device.
Does the validator check for accessibility issues?
The validator reports structural issues like missing alt attributes and landmark roles, but for a full accessibility audit you should also use a dedicated tool like axe or Lighthouse.
Will it validate HTML5 custom elements and data attributes?
Custom elements and data-* attributes are part of the HTML5 spec and will pass validation without errors.