Use Hreflang Tags for Language and Regional URLs

Many websites serve users from around the world with content translated or targeted to users in a certain region. Google uses the rel="alternate" hreflang="x" attributes to serve the correct language or regional URL in Search results.

Some example scenarios where rel="alternate" hreflang="x" is recommended:

• You keep the main content in a single language and translate only the template, such as the navigation and footer. Pages that feature user-generated content like a forums typically do this.
• Your content has small regional variations with similar content in a single language. For example, you might have English-language content targeted to the US, GB, and Ireland.
• Your site content is fully translated. For example, you have both German and English versions of each page.

Using language annotations

Imagine you have an English language page hosted at http://www.example.com/, with a Spanish alternative at http://es.example.com/. You can indicate to Google that the Spanish URL is the Spanish-language equivalent of the English page in one of three ways:

• HTML link element in header. In the HTML section of http://www.example.com/, add a link element pointing to the Spanish version of that webpage at http://es.example.com/, like this:

• HTTP header. If you publish non-HTML files (like PDFs), you can use an HTTP header to indicate a different language version of a URL:

  Link: ; rel="alternate"; hreflang="es"

• Sitemap. Instead of using markup, you can submit language version information in a Sitemap.

 You can specify multi-language URLs in the same domain as a given URL, or use URLs from a different domain







Read more .. https://support.google.com/webmasters/answer/189077?hl=en