Google Begins Rolling Out March Core Algorithm Update via @sejournal, @MattGSouthern

Google has officially begun rolling out its March 2025 core algorithm update, according to an announcement posted to the Google Search Status Dashboard today.

The update commenced at 9:23 AM PDT and is expected to fully deploy across all of Google’s search systems in up to two weeks.

The company provided minimal details beyond the timing and expected duration of the rollout.

The official announcement reads:

“Released the March 2025 core update. The rollout may take up to 2 weeks to complete.”

What This Means For SEO Professionals

Core updates are comprehensive changes to Google’s main search algorithms and systems.

Unlike more minor updates that might focus on specific issues, core updates typically produce noticeable changes to search rankings across the web.

Website owners and SEO professionals should expect fluctuations in search visibility and rankings over the coming weeks as the update gradually rolls out.

These changes often stabilize once the update is fully implemented, though permanent shifts in positioning can occur based on how the new algorithm evaluates content quality and relevance.

Preparing For Algorithm Changes

As with previous core updates, Google hasn’t provided specific details about changes made to its ranking systems. The company typically advises creating high-quality content rather than trying to fix particular issues when rankings drop after an update.

Monitor your analytics during this period to identify any significant changes in traffic or rankings. Documenting these changes can help determine whether adjustments are needed once the update has been fully implemented.

Search Engine Journal will continue to monitor the impact of this update and provide additional information as it becomes available.

Google Publishes New Robots.txt Explainer via @sejournal, @martinibuster

Google published a new Robots.txt refresher explaining how Robots.txt enables publishers and SEOs to control search engine crawlers and other bots (that obey Robots.txt). The documentation includes examples of blocking specific pages (like shopping carts), restricting certain bots, and managing crawling behavior with simple rules.

From Basics To Advanced

The new documentation offers a quick introduction to what Robots.txt is and gradually progresses to increasingly advanced coverage of what publishers and SEOs can do with Robots.txt and how it benefits them.

The main point of the first part of the document is to introduce robots.txt as a stable web protocol with a 30 year history that’s widely supported by search engines and other crawlers.

Google Search Console will report a 404 error message if the Robots.txt is missing. It’s okay for that to happen but if it bugs you to see that in the GSC you can wait 30 days and the warning will drop off. An alterative is to create a blank Robots.txt file which is also acceptable by Google.

Google’s new documentation explains:

“You can leave your robots.txt file empty (or not have one at all) if your whole site may be crawled, or you can add rules to manage crawling.”

From there it covers the basics like custom rules for restricting specific pages or sections.

The advanced uses of Robots.txt covers these capabilities:

• Can target specific crawlers with different rules.
• Enables blocking URL patterns like PDFs or search pages.
• Enables granular control over specific bots.
• Supports comments for internal documentation.

The new documentation finishes by describing how simple it is to edit the Robots.txt file (it’s a text file with simple rules), so all you need is a simple text editor. Many content management systems have a way to edit it and there are tools available for testing if the Robots.txt file is using the correct syntax.

Read the new documentation here:

Robots Refresher: robots.txt — a flexible way to control how machines explore your website

Featured Image by Shutterstock/bluestork

Is Google’s Use Of Compressibility An SEO Myth? via @sejournal, @martinibuster

I recently came across an SEO test that attempted to verify whether compression ratio affects rankings. It seems there may be some who believe that higher compression ratios correlate with lower rankings. Understanding compressibility in the context of SEO requires reading both the original source on compression ratios and the research paper itself before drawing conclusions about whether or not it’s an SEO myth.

Search Engines Compress Web Pages

Compressibility, in the context of search engines, refers to how much web pages can be compressed. Shrinking a document into a zip file is an example of compression. Search engines compress indexed web pages because it saves space and results in faster processing. It’s something that all search engines do.

Websites & Host Providers Compress Web Pages

Web page compression is a good thing because it helps search crawlers quickly access web pages which in turn sends the signal to Googlebot that it won’t strain the server and it’s okay to grab even more pages for indexing.

Compression speeds up websites, providing site visitors a high quality user experience. Most web hosts automatically enable compression because it’s good for websites, site visitors and also good for web hosts because it saves on bandwidth loads. Everybody wins with website compression.

High Levels Of Compression Correlate With Spam

Researchers at a search engine discovered that highly compressible web pages correlated with low-quality content. The study called Spam, Damn Spam, and Statistics: Using Statistical Analysis to Locate Spam Web Pages  (PDF) was conducted in 2006 by two of the world’s leading researchers, Marc Najork and Dennis Fetterly.

Najork currently works at DeepMind as Distinguished Research Scientist. Fetterly, a software engineer at Google, is an author of many important research papers related to search, content analysis and other related topics. This research paper isn’t just any research paper, it’s an important one.

What the research paper shows is that 70% of web pages that compress at a level of 4.0 or higher tended to be low quality pages with a high level of redundant word usage. The average compression level of sites was around 2.0.

Here are the averages of normal web pages listed by the research paper:

• Compression ratio of 2.0:
  The most frequently occurring compression ratio in the dataset is 2.0.
• Compression ratio of 2.1:
  Half of the pages have a compression ratio below 2.1, and half have a compression ratio above it.
• Compression ratio of 2.11:
  On average, the compression ratio of the pages analyzed is 2.11.

It would be an easy first-pass way to filter out the obvious content spam so it makes sense that they would do that to weed out heavy-handed content spam. But weeding out spam is more complicated than simple solutions. Search engines use multiple signals because it results in a higher level of accuracy.

The researchers reported that 70% of sites with a compression level of 4.0 or higher were spam. That means that the other 30% were not spam sites. There are always outliers in statistics and that 30% of non-spam sites is why search engines tend to use more than one signal.

Do Search Engines Use Compressibility?

It’s reasonable to assume that search engines use compressibility to identify heavy handed obvious spam. But it’s also reasonable to assume that if search engines employ it they are using it together with other signals in order to increase the accuracy of the metrics. Nobody knows for certain if Google uses compressibility.

Is There Proof That Compression Is An SEO Myth?

Some SEOs have published research analyzing the rankings of thousands of sites for hundreds of keywords. They found that both the top-ranking and bottom-ranked sites had a compression ratio of about 2.4. The difference between their compression ratios was just 2%, meaning the scores were essentially equal. Those results are close to the normal average range of 2.11 reported in the 2006 scientific study.

The SEOs claimed that the mere 2% higher compression levels of the top-ranked sites over the bottom-ranked sites prove that compressibility is an SEO myth. Of course, that claim is incorrect. The average compression ratio of normal sites in 2006 was 2.11, which means the average 2.4 ratio in 2025 falls well within the range of normal, non-spam websites.

The ratio for spam sites is 4.0, so the fact that both sets of top and bottom ranked sites are about 2.4 ratio is meaningless since both scores fall within the range of normal.

If we assume that Google is using compressibility, a site would have produce a compression ratio of 4.0, plus send other low quality signals, to trigger an algorithmic action. If that happened those sites wouldn’t be in the search results at all because they wouldn’t be in the index and therefore there is no way to test that with the SERPs, right?

It would be reasonable to assume that the sites with high 4.0 compression ratios were removed. But we don’t know that, it’s not a certainty.

Is Compressibility An SEO Myth?

Compressibility may not be an SEO myth. But it’s probably not anything publishers or SEOs should be worry about as long as they’re avoiding heavy-handed tactics like keyword stuffing or repetitive cookie cutter pages.

Google uses de-duplication which removes duplicate pages from their index and consolidates the PageRank signals to whichever page they choose to be the canonical page (if they choose one). Publishing duplicate pages will likely not trigger any kind of penalty, including anything related to compression ratios, because, as was already mentioned, search engines don’t use signals in isolation.

U.S. DOJ Antitrust Filing Proposes 4 Ways To Break Google’s Monopoly via @sejournal, @martinibuster

The plaintiffs in an antitrust lawsuit against Google filed a revised proposed final judgment for the judge in the case to consider. The proposal comes after a previous ruling where the court determined that Google broke antitrust laws by illegally maintaining its monopoly.

The legal filing by the plaintiffs, the United States Department Of Justice and State Attorneys General, argue that Google has maintained monopolies in search services and text advertising through anticompetitive practices.

The filing proposes four ways to loosen Google’s monopolistic hold on search and advertising.

1. Requiring Google to separate Chrome from its business—this could mean selling it or spinning it off into an independent company.
2. Limiting Google’s payments to companies like Apple for making Google the default search engine, reducing its ability to secure exclusive deals.
3. Stopping Google from favoring its own products over competitors in search results and other services, ensuring a more level playing field.
4. Increasing transparency in Google’s advertising and data practices so competitors have fairer access to key information.

The proposal asks that Google be subjected to continuous oversight through mandatory reporting to ensure transparency in Google’s advertising and data practices:

“Google must provide to the Technical Committee and Plaintiffs a monthly report outlining any changes to its search text ads auction and its public disclosure of those changes.”

It also suggests ongoing enforcement to guarantee that Google doesn’t impose new restrictions that undermine transparency requirements:

“Google must not limit the ability of advertisers to export in real time (by downloading through an interface or API access) data or information relating to their entire portfolio of ads or advertising campaigns bid on, placed through, or purchased through Google.”

The goal of the above section is to increase transparency in Google’s advertising system and make it easier for advertisers to analyze their ad performance, greater transparency.

Real-time access ensures advertisers can make immediate adjustments to their campaigns instead of waiting for delayed reports and it assures that advertisers aren’t locked into the Google advertising system by holding them hostage to their historical data.

The legal filing requires government-imposed restrictions and changes to Google’s advertising business practices. It proposes remedies for how Google should be regulated or restructured following the court’s earlier ruling that Google engaged in monopolistic practices. However, this is not the final judgment and the court must still decide whether to adopt, modify, or reject these proposed remedies.