We know the bulk, if not all, of the Google mobile friendly algorithm is based on the user experience of the mobile site, so UX is a ranking factor on mobile. But when it comes to desktop, UX (user experience) is not a ranking factor there.
Google's Gary Illyes confirmed this on Twitter saying "On desktop currently no," there is no UX ranking signal on desktop. Here is the tweet:
He did go on to say at SMX Sydney that UX will never be more important than content for ranking purposes.
So while UX is a mobile ranking factor, it currently is not a desktop ranking factor.
Forum discussion at Twitter.