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Broken HTML Checker

Scan your page for broken HTML — invalid nesting, duplicate IDs, missing required attributes, and deprecated tags — that hurt SEO and accessibility.

What is Broken HTML Checker?

Broken HTML refers to markup errors in your webpage's source code — such as unclosed tags, improperly nested elements, duplicate IDs, missing required attributes, or the use of deprecated elements. These issues can cause rendering problems across browsers, hurt accessibility, and negatively impact your SEO rankings.

How to Fix It

Review the flagged issues and fix them in your HTML source code or templating system. Ensure all tags are properly opened and closed, elements are nested correctly according to HTML specifications, and required attributes (like alt on images) are present. Use an HTML validator regularly during development.

Best Practices

  • Always close HTML tags properly — avoid orphaned or mismatched tags.
  • Use unique IDs across the entire page to prevent duplicate ID errors.
  • Nest elements according to HTML5 spec (e.g., don't put block elements inside inline elements).
  • Include required attributes like alt on images and type on scripts.
  • Replace deprecated elements (e.g., <center>, <font>) with modern CSS-based alternatives.
  • Validate your HTML regularly using automated tools during your build process.