As you may know, Google has been focusing on how it can better rank mobile search results. The big news last week was that it added a "Mobile-Friendly" label to results, and would give such sites a ranking boost.
Google said this week that it will still use desktop signals for ranking mobile results. John Mueller (who we'll pretty much consider the new Matt Cutts at this point) talked about this in a Webmaster Central hangout (via Search Engine Roundtable):
The subject comes up at about 18 minutes and 50 seconds into the video, when someone asked him if it is correct that Google uses the page speed of a site's desktop version as a ranking signal for the mobile version. He said that this is correct at the moment (he thinks...he tends not to completely commit to a lot of these answers).
Mueller went on to say:
So we need to focus on the desktop page for the search results for the most part. That's also the one that you use with the rel canonical. As we pick up more information from mobile friendly pages or from mobile pages in general, then I would expect that to flow into the rankings as well. So that's something to keep in mind there.
I'd still make sure that your mobile friendly pages are as fast as possible, that they work really well on mobile devices, that you're going past just essentially the required minimum that we had with the mobile friendly tool, and really providing a great experience on mobile. Because lots of people are using mobile to kind of make their decisions, to read content, and if your site is kind of minimally usable on mobile, but really a bad user experience, really, really slow, then that's something that users will notice as well and they'll jump off and do something else or go to a different site.
It's pretty much common sense that you want your site to be as optimal as possible, but it is interesting that Google is still using desktop signals, especially considering that there are likely more signals to glean from mobile devices.
Image via YouTube