Google announced on the Webmaster blog that they are going to be boosting the effects of the mobile-friendly algorithm they launched back on April 21, 2015.
Google said the update will happen “beginning in May,” and it “increases the effect of the [mobile-friendly] ranking signal.” Google said if you are already mobile-friendly, you do not have to worry, because “you will not be impacted by this update.”
When the update happens, it will roll out gradually, so you won’t see a major drop-off on non-mobile-friendly websites when the algorithm is pushed out. This kind of sounds like the slow Panda 4.2 rollout, but it is unclear if the rollout will take weeks or months. Google just said it would “start rolling out” the update in the beginning of May.
The mobile-friendly algorithm is a page-by-page signal, so it can take time for Google to assess each page, and that may be why it will be a gradual rollout. And depending on how fast Google crawls and indexes all of the pages on your site, the impact can be slow to show up.
It is believed that this rollout will have less impact than the original mobile-friendly update, which was called “Mobilegeddon.” The original Mobilegeddon was supposed to have a significant impact on the mobile results, but not everyone said it had that much of an impact.
If you are not mobile-friendly, or if you want to ensure you are, check the Google mobile-friendly tool, and check Google’s mobile guidelines.