html.lang-missing

What to change

A finding of this rule on a page carries the exact edits for that page: the markup it quotes, and what to write instead.

When it runs

Runs on every SEO audit: of a page, a crawl, a build directory or HTML. A warning is a problem that costs a page ranking, clicks or citations. Each finding takes 5 points off the page's score.

The severity here is the rule's usual one: a finding can be raised or lowered when the page gives a reason.

Run it, or skip it

Check a page for this rule alone, after a fix for instance:

npx @rivi-software/agentic-seo-check audit https://example.com --rule html.lang-missing

Or from an assistant, with the MCP tool seo_audit_page:

{
  "url": "https://example.com",
  "rules": [
    "html.lang-missing"
  ]
}

To leave it out of an audit, pass --disable html.lang-missing on the command, or disableRules: ["html.lang-missing"] to a tool.

• Warninghtml.lang-invalidThe <html lang> value is not a valid BCP 47 language tag.
• Warningviewport.missingNo <meta name="viewport"> is present, so the page is not mobile-friendly.
• Infoviewport.not-scalableThe viewport disables user zoom (user-scalable=no or maximum-scale=1).
• Infocharset.missingNo character encoding is declared, in the HTML or in the Content-Type header.
• Infodoctype.missingThe document does not start with <!DOCTYPE html>.
• Infodocument.html-too-largeThe HTML document is larger than 1.5 MB.
• Errorhead.closed-earlyAn element that does not belong in <head> (an <img>, <iframe>, <div>, stray text) ends it early, so search engines read the metadata after it as part of <body> and ignore it.
• Warninghead.metadata-in-bodyMetadata that search engines read only in <head> (title, meta description, viewport, canonical, hreflang) is written in <body> (warning). Metadata a framework streams into a hidden part of <body> and moves into <head> with JavaScript, as Next.js does for an async generateMetadata, is info. Robots meta tags are not reported: Google honours them in <body> too.