Will ranking be affected with a mobile XML sitemap for a mobile site with the same URLs as the desktop site?

Question

We have a site with both a desktop version and a mobile version. Most of the content are the same and both versions have the same URL, but the HTML generated is device specific.

Looking at Google's recommendations for smartphone-optimized sites, one could get the impression that the mobile xml sitemap is only for sites with different URLs.

Will ranking be affected - negatively or positively - if we add a mobile xml sitemap that effectively will be a duplicate of the desktop sitemap?

Answer 1

A Sitemap, mobile or otherwise, won't directly affect rankings in any case. The main problem you face is the wrong content getting into the wrong Google index (i.e. mobile/desktop). As per the recommendations you've read, the Vary HTTP header is important if serving different content on the same URLs.

Answer 2

I've ran into that same issue, where my template will change depending on the user's device that is being used to browse the site. And from my experience Google will only acknowledge one sitemap if they look very similar in Google Webmaster Tools, you may not even need a Mobile XML Sitemap because your viewers will automatically be taken to the mobile page when click on your listing in a search.