International SEO hreflang tags implemented correctly

Missing or misconfigured hreflang annotations cause Google to serve the wrong language version to users — French visitors land on English pages, bounce rates spike, and both versions compete for the same queries. Missing x-default means users from unlisted regions get an arbitrary variant instead of your canonical fallback, which degrades conversion on international traffic that you're already spending to acquire.

Declare every locale variant plus x-default on every page that has translations. Implement in app/[locale]/layout.tsx:

export async function generateMetadata({ params }) {
  return {
    alternates: {
      canonical: `https://yoursite.com/${params.locale}`,
      languages: { en: '/en', fr: '/fr', 'x-default': '/en' }
    }
  }
}

• ID: seo-advanced.crawlability.hreflang-implementation

• Severity: info

• What to look for: Count all language or region variants served by the site (e.g., /en/, /fr/, /de/ routes or locale subdomains). For each page with language variants, check for <link rel="alternate" hreflang="..."> tags or hreflang attributes in the XML sitemap. Verify x-default is specified for the default language version. Enumerate the hreflang tags found per page.

• Pass criteria: For multilingual/multi-regional sites, at least 90% of pages with language variants include hreflang tags listing all available languages, plus an x-default tag for the default version. Report: "X language variants detected; Y of Z pages have complete hreflang tags."

• Fail criteria: Fewer than 90% of multilingual pages have hreflang tags, or x-default is missing from any page with hreflang tags.

• Skip (N/A) when: Site serves only 1 language and 1 geographic region (no locale routes, no language subdomains).

• Detail on fail: "Site has /en and /fr versions; 5 of 12 pages lack hreflang tags" or "hreflang tags present on all pages but x-default not specified on 3 pages".

• Remediation: Add hreflang tags to multilingual pages in app/[locale]/layout.tsx:

  export const metadata = {
    alternates: {
      languages: {
        en: 'https://yoursite.com/en/page',
        fr: 'https://yoursite.com/fr/page',
        'x-default': 'https://yoursite.com/page',
      },
    },
  }