On the 24th of September, Google has announced a new core update. The update, as the two previous ones, was announced via Twitter. The first one was rolled out on 12th March, and the second one on 18th June.

Later today, we are releasing a broad core algorithm update, as we do several times per year. It is called the September 2019 Core Update. Our guidance about such updates remains as we’ve covered before. Please see this blog for more about that: https://t.co/e5ZQUAlt0G

— Google SearchLiaison (@searchliaison) September 24, 2019

A Google core update happens every 4 or so months and the main goal is to adjust its core search ranking algorithm to return more important and useful search results for users. Google updates are very important especially for webmasters and SEOs all around the world because all changes are global. They are also often to blame when a website suffers a sudden drop in SEO visibility or ranking. Danny Sullivan, Google's Search Liaison Officer, presented some details on the September update saying on Twitter that it will start on the 24th September, will take a few days to be fully completed and that the update will affect all global search indexes. 

I expect it to begin in a few hours; these typically take a few days to fully roll out. Yes, we'll post when the rollout begins. We don't post when it ends because there's typically other updates that are always happening, too. But after a few days, as said.

— Danny Sullivan (@dannysullivan) September 24, 2019

As of September 30rd, a full impact of the September Core Update is now being felt. Some pages have gone from page 10+ to 2-5 but another ones got hit even as much as -30% decrease in traffic. Looking at various data published at Twitter and different sites or blogs, it seems that September Core update was „weaker" than the June one. In overall, September Core update have had the strongest impact on YMYL category („your money - your life").