Google: It Takes ~28 Days to See Changes in Search Results After This Type of Improvement

Google says that after making speed changes that affect Core Web Vitals, it can take 28 days before you see results.
SIA Team
October 26, 2021

During the English Google SEO office-hours from October 22, 2021, John Mueller was addressing a question (as he usually does during these sessions). 

At around the 26:29 mark, John began reading and addressing a question about improvements and hopeful search results. 

(Basically, a person who submitted a question said they had made improvements, and wanted to know how reliable the observed ranking improvements were. Were they a direct result of the changes made?)

You can watch that at the video below, which is queued to the appropriate time. 

While addressing the question, John mentioned something important: 

“One thing maybe worth mentioning, specifically about speed, is that for the Core Web Vitals, we take into account the data that is, I think, delayed by 28 days, or something like that. 

“So about a month back. Which means if you make significant speed changes on your website that affect the Core Web Vitals, and accordingly the Page Experience ranking factor, then I would expect it to take about a month to be visible in the search results.”

I think it’s rare that you hear Google give a quantified number of days for anything pertaining to search engine improvements. 

This is one of those rare times. 

Take advantage of it

Source: Google Search Central YouTube channel