Up until now, Google has always measured page speed by using the desktop version of a site as a reference. However, with the introduction of the Mobile First index, all of this looks set to change, with Gary Illyes recently announcing that Google have been busily reworking the algorithm to take mobile speed more seriously.
According to Gary, the reason for this is that Desktop speeds are much less important than mobile, particularly with the large increase in the number of mobile users who are often lumbered with much slower connection speeds.
Google themselves have, in the past, been relatively unclear as to whether or not page speed will have a sign cant affect on SEO when the mobile first index is finally launched. They initially claimed that it would not really matter – before then saying it would. Of course, now it’s official, it looks like everyone will have to take mobile website optimization much more seriously.
With the mobile first index expected to be launched at the start of 2018, Gary Illyes has also announced that Google are going to be highly vocal about the importance of mobile page speed as a contributory ranking factor when the new algorithm is introduced.