The source is fetched and checked server-side – the raw HTML as a search-engine crawler first sees it (not the JavaScript-rendered DOM). In addition, HTTP status, redirects, security headers and structured data are evaluated.
Need to check several pages at once? Bulk validation is available via Search-Console.PRO.
Paste HTML or load an example to start checking.
What this validator analyses
Syntax & nesting
A custom tokenizer reads the raw markup – not the browser parser that silently repairs. That way it finds unclosed and mis-nested tags, open quotation marks, duplicate attributes and typos in element names.
Semantics & structure
Doctype, language, character set, exactly one <h1>, a gap-free heading outline and a clean <main> – the foundation for search engines and screen readers.
Accessibility & SEO
Missing alt text, unlabelled fields, duplicate IDs, title and description lengths, Open Graph tags and canonicals – concise, with concrete recommendations.
Over 30 individual checks
- Missing or outdated doctype
- Unclosed tags
- Incorrect nesting
- Open attribute quotes
- Duplicate attributes
- End tags on void elements
- Unknown element names
- Deprecated tags (font, center, …)
- Deprecated attributes (align, bgcolor, …)
- Missing
langattribute - Missing character set
- Missing viewport meta
- Title presence & length
- Meta description & length
- Exactly one
<h1> - Jumps in the outline
- Exactly one
<main> - Images without
alt - Images without dimensions (CLS)
- Empty or href-less links
target=_blankohne noopener- Buttons without a name
- Fields without a label
- Duplicate IDs
tabindex> 0- Canonical & Open Graph
- Inline events & styles
- Self-closing non-void tags