A common setup would be pages on www.example.com serving desktop users with corresponding pages served on m.example.com for mobile users. Google does not favor any particular URL format as long as they are all accessible for all Googlebot user-agents.
Separate mobile URLs serve different code to desktop and mobile devices (and perhaps even tablets), and on different URLs.
We support two methods to have this annotation: in the HTML of the pages themselves and in sitemaps. For example, suppose that the desktop URL is http://example.com/page-1 and the corresponding mobile URL is http://m.example.com/page-1. The annotations in this example would be as follows.
Annotations in the HTML
On the desktop page (http://www.example.com/page-1), add:
<link rel="alternate" media="only screen and (max-width: 640px)"
href="http://m.example.com/page-1">
and on the mobile page (http://m.example.com/page-1), the required annotation should be:
<link rel="canonical" href="http://www.example.com/page-1">
This rel="canonical" tag on the mobile URL pointing to the desktop page is required.
Annotations in sitemaps
We support including the rel=”alternate” annotation for the desktop pages in sitemaps like this:
<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
xmlns:xhtml="http://www.w3.org/1999/xhtml">
<url>
<loc>http://www.example.com/page-1/</loc>
<xhtml:link
rel="alternate"
media="only screen and (max-width: 640px)"
href="http://m.example.com/page-1" />
</url>
</urlset>
The required rel="canonical" tag on the mobile URL should still be added to the mobile page’s HTML.
