Google announced it is testing new pre-fetching methods that increase the speed (Largest Contentful Paint - LCP) of the first two results by 67 milliseconds and for the results after those by about by 9.5 milliseconds.
Barry Pollard and Oleksiy Busaryev from Google wrote on the Google Chrome Developer blog, "Google Search has been making use of the Speculation Rules API to improve navigation speed from the search results page to the result links and they've been using a few features of the API that may be of interest to other site owners."
Google is prefetching the first two results to help with these gains by using privacy-preserving prefetches, the private prefetch proxy in Chrome. And also, by using the referrer_policy setting to ensure no details encoded in the search page's URL are sent to the site in the referer HTTP header. Google added that a third protection automatically happens if the user has cookies for the site. In this case, they may receive different results based on those cookies, and Chrome won't use the prefetched HTML.
The results:
Google said it saw a "significant improvements in Largest Contentful Paint (LCP)." On Chrome for Android, LCP for clicks from Google Search were reduced by 67 milliseconds. A followup launch for desktop Chrome resulted in a similar improvement in LCP of 58.6 milliseconds.
Then beyond those first two results there were gains also. Google said, "Desktop Chrome reduced First Contentful Paint (FCP) for navigations from Google Search by 7.6 milliseconds and LCP by 9.5 milliseconds (as shown by A/B testing). These represent smaller gains compared to the 58.6 milliseconds improvements seen in the first two results, but that's not surprising given the smaller lead time as they are not prefetched as eagerly."
