Google has already begun rolling out its mobile-first index to some users, but there are still a lot of questions about how exactly the search engine’s new separate index actually functions.
One such question got a surprising answer yesterday during the Google State of Search conference, as Maile Ohye told the audience that Google won’t index the AMP version of your page in the mobile search index – even when you don’t have a mobile-friendly alternative.
— Jennifer Slegg (@jenstar) November 14, 2016
Google’s Gary Illyes also confirmed the news on Twitter after the conference:
@AlanBleiweiss yeah. I should've said that if you make the amps your pages' mobile version, then amps would be picked
— Gary "鯨理" Illyes (@methode) November 16, 2016
That means if you’ve been using AMP pages as an alternative to making your website mobile-friendly, the search engine will skip over indexing your AMP pages in the mobile-friendly search index. Instead, it will by default choose to index the desktop version within its older index.
There is a way to force Google to index your AMP pages in this situation using a rel alternate attribute, but otherwise Google’s index will default to your desktop versions of pages.
This is particularly surprising because Google has pushed AMP as the ultimate way to deliver content to mobile users quickly and without losing ad revenue. But, in this case it seems the streamlined design of AMP pages leaves something to be desired. It may be the lack of site navigation options is what made Google decide to favor desktop over AMP in their index.
This change will most likely only affect a very small number of websites, but it is an odd choice for the search engine. The vast majority of websites who have adopted AMP also maintain a mobile version of their site.