About the HTML Validator
Clean, semantic HTML is the foundation of accessible, performant, and SEO-friendly web applications. While browsers will attempt to fix broken markup automatically, structural errors like duplicate IDs, unclosed tags, and missing accessibility attributes can cause severe styling bugs and screen reader failures. This HTML Validator scans your markup for common structural defects.
This tool is valuable for frontend developers, accessibility (a11y) auditors, and content editors. It inspects markup for duplicate 'id' attributes, unclosed elements, mismatched closing tags, <img> elements missing 'alt' descriptions, and empty <a> links.
To use the tool, paste your HTML snippet into the editor and click 'Validate HTML Structure'. The validator categorizes findings by severity: Errors (broken nesting, duplicate IDs), Warnings (missing doctype, missing alt tags), and Info notices.
For example, having two '<div id="main">' elements on the same page will trigger an Error alert indicating that element IDs must be globally unique across the DOM.
A common HTML mistake is omitting the 'alt' attribute on image tags. Even for purely decorative images, an empty 'alt=""' should be specified so screen readers know to skip them.
Tip: Run your HTML email templates and component markup through this validator before shipping to avoid cross-browser rendering quirks.