Mark-up for desktop and separate mobile version of site, can they be used cross domain?

Question

When there is a separate mobile version of a site on a different URL to the main site, Google suggests to use their Annotations for desktop and mobile URLs.

On the desktop page, add:

<link rel="alternate" media="only screen and (max-width: 640px)"
      href="http://m.example.com/page-1" >

and on the mobile page, the required annotation should be:

<link rel="canonical" href="http://www.example.com/page-1" >

Can these be used cross domain?

e.g:

Desktop site: www.example.com

Mobile site on a different domain: www.example.mobile

I know this is the possibly the worst way to set up a mobile version of a site, but say in a worst case scenario, could they work?

I'm thinking most likely not, however canonical tags can be used cross domain, so in theory it might work.

Answer 1

Sure, cross-domain is fine. Using .mobi was very popular for a while, other sites just use "m.theirdomain.com", it's essentially up to you. Keep in mind that multiple domains for the same site does increase the maintenance overhead, but that's ultimately your decision.