seo – Google deindexes our desktop site after launching a separate mobile site with fewer pages

For pages containing desktop and mobile versions:

  • On your exemple.com page, put a canonical showing the exemple.com page and a alternate showing the m.exemple.com page.

  • On your m.exemple.com page, put a canonical showing the exemple.com page.

For pages where you only have one desktop version:

  • On your exemple.com page, put a canonical pointing to exemple.com page and do not use a alternate tag (because there is no alternative representation).

  • Leave your m.exemple.com non existing page.

This configuration ensures that Google will always index your exemple.com pages as canonical pages and not to confuse and index everything m.exemple.com pages, because it will see them as an alternative resource representation.

When a visitor visits your exemple.com page, detects if they are on a mobile device. If they are both on a mobile device and you also have a mobile representation of the displayed page, redirect them to the page. m.exemple.com version of the page.