HTML Validator / Syntax Checker

Detect unclosed tags, missing attributes, and common HTML syntax errors.
Errors: Warnings: Valid HTML
Paste HTML or upload a file

Click Validate to check your HTML for issues.

No issues found!

Your HTML looks valid.

Checks Performed
Note: This is a client-side syntax checker. For full W3C validation, use the official W3C Markup Validator.

Features

  • Unclosed Tags: Detects tags that are opened but never closed.
  • Mismatched Tags: Finds closing tags that don't match the last opened tag.
  • Missing Alt Text: Warns when <img> tags lack an alt attribute.
  • Deprecated Tags: Flags outdated elements like <center>, <font>, <marquee>.
  • Inline Style Warning: Notes excessive use of inline styles.
  • Doctype Check: Warns if no DOCTYPE declaration is present.
  • File Upload: Upload an .html file directly.

How to Use

  1. Paste or Upload: Paste HTML or upload a file.
  2. Validate: Click the "Validate" button.
  3. Review Issues: Errors (red) are serious problems; warnings (yellow) are best practices.
  4. Fix & Re-validate: Edit the HTML and validate again.