Google is testing another variation of “back to top” in the mobile search results, to make it easier for searchers who want to quickly jump back to the top of the search results page, rather than continuing on to the second page of results.
Here is how it looks:
Google was earlier testing a version that would add a blue overlay on top of the search results, that would show up when someone started scrolling further down the mobile search results. This earlier version was much more noticeable and I could see it getting a higher CTR for people wanting to jump back to the top of the search results.
By contrast, this new one is not very noticeable at all, especially since it is placed below the “next” button at the bottom of the search results.
This seems to be a limited test as I was unable to replicate it.
H/T to Sergey Alakov