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' }
    }
  }
}