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Page Language Not Declared

Without lang="en" on <html>, screen readers may use the wrong pronunciation and Google cannot reliably detect the page language.

notice Impact: medium WCAG 3.1.1 (Level A) HTML_LANG_MISSING 2 min read Updated

Why it matters

Without lang="en" on <html>, screen readers may use the wrong pronunciation and Google cannot reliably detect the page language.

Address when convenient — notices usually mark a polish opportunity rather than a defect. Estimated SEO impact: medium — measurable effect on click-through or relevance.

How to fix

  • Add lang="en" (or correct language code) to <html>
  • Use sub-elements with their own lang="..." for multi-lingual sections

Common causes

If the rule is firing across many pages, the root cause is almost always one of these:

  • Mixed-content sub-resources from before HTTPS migration that escaped the rewrite.
  • CDN or upstream proxy strips a security header that was set at the origin.
  • Legacy redirects send HTTPS traffic through HTTP first.
  • Test/staging hostnames leak into production HTML via hard-coded URLs.

Anti-patterns to avoid

Even with the best intentions, these "fixes" make the issue worse — recognise them so you don't ship them:

  • Mixed HTTP/HTTPS resources after migration.
  • Self-signed or expired certificates on production.
  • Long-lived secrets in client-rendered HTML or JS bundles.

How atlookup detects this

Our crawler renders each page with a real headless browser, then inspects HTTPS state, response headers, mixed content, and certificate validity. Pages where the rule fires for page language not declared are flagged on the report.

If you'd like to see this rule fire on your own site, run a free 60-second audit — every page is reported with the exact lines that triggered it.

Tools to verify the fix

Once you've applied the fix, double-check with these external validators:

Frequently asked questions

Why does Page Language Not Declared matter for SEO?

Without lang="en" on <html>, screen readers may use the wrong pronunciation and Google cannot reliably detect the page language.

How do I fix page language not declared?

Add lang="en" (or correct language code) to <html> Use sub-elements with their own lang="..." for multi-lingual sections

Is this a critical SEO issue?

Address when convenient — notices usually mark a polish opportunity rather than a defect. Estimated SEO impact: medium — measurable effect on click-through or relevance.

How does atlookup detect page language not declared?

Our crawler renders each page with a real headless browser, then inspects HTTPS state, response headers, mixed content, and certificate validity. Pages where the rule fires for page language not declared are flagged on the report.

Does this affect accessibility?

Yes. This issue maps to WCAG 3.1.1 (Level A). Fixing it improves both SEO ranking signals and the experience for users on assistive technology.

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