This post will continue to be updated as new information becomes available.
What Does This Mean for Website Owners?
Earlier this week Google announced a broad core algorithm update. Google updates their search algorithm regularly (mostly goes unnoticed), but a few times per year these updates are significant and usually result in noticeable losses or gains of website traffic – often, in certain categories.
Because of this, core updates are always something to keep an eye on – especially during the weeks that these updates roll out it's important to monitor for changes and wait until the industry's consensus fully develops before deciding on an action. Often, our work here starts post factum.
I'd recommend checking out this post on Google's Webmaster Central Blog about what webmasters should know about core algorithm updates. I find it very detailed, and it includes links to some excellent content and studies from well-known SEOs.
Also, many expressed concerns about the timing of this update. The argument is that many businesses are struggling as is, and for quite a few Google traffic is business critical. There's a lot of depth to it and makes for an interesting debate at least.
I find this interview with Kristine Schachinger incredibly insightful and recommend watching it for a better understanding of the mechanics of core updates and site recovery.
It's important to understand that correlation doesn't imply causation. Nevertheless, what we see frequently on websites that experience traffic loss after a core update is multiple technical SEO issues.
This was also true during the March 2019 Google Core Update that shook up the health industry, with many of the websites that were affected being plagued by technical problems.
My recommendation is that if you're looking to start somewhere after being hit by a core update, a technical audit is a good starting point. First, make sure that there are no technical issues affecting your website before looking into content quality etc. And if you were aware about certain issues (e.g. pagespeed, server errors etc.) but you were postponing the fixes because traffic was growing and there was no immediate threat, I would prioritize fixing these right away.
Update (14 May 2020): Here is a very in-depth analysis of the effect of the update from Moz's marketing scientist Dr. Peter J. Meyers. A lot of thought went into the methodology behind this analysis and it goes beyond the typical traffic comparison between two points in time (before/after). It is also the first major study I've come accross after the dust has kind of settled.
As he points out, the index/ rankings fluctuate daily and thus a simple chronological comparison isn't a very accurate method for determining the effect of a core update. Last but not least, May's core update happened after a period of abnormally high ranking fluctuations. This ads another degree of inaccuracy to direct traffic comparison studies.
Update (18 May 2020): The core update rollout is now complete.