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HTML validator — check HTML syntax online

Validate HTML markup using the browser's native DOMParser, detecting unclosed tags, invalid nesting, and structural errors

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HTML validator
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HTML-specific

Why validate your HTML?

Invalid HTML leads to rendering inconsistencies across browsers, broken accessibility trees, and failed SEO crawls. QuickKit's HTML validator parses your markup using the browser's native DOMParser — the same engine that renders web pages — and reports parse errors and structural issues accurately. Unlike tools that guess at HTML errors, this validator uses the actual browser parsing algorithm. It catches unclosed tags, invalid attribute syntax, malformed entities, and nesting violations. Especially useful for validating HTML generated by templating systems, CMS exports, or web scraping before using it in your own pages.

Questions

Frequently asked questions

No — this uses the browser's native HTML parser (forgiving algorithm). W3C validation is stricter. For accessibility and spec compliance, use the W3C validator.
The parser validates attribute syntax (proper quoting, valid names) but not semantic validity (e.g., whether an aria-role value is a valid ARIA role).
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