Google’s Gary Illyes: The Lastmod Signal Is Binary

  • June 11, 2024
  • SEO
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In a recent LinkedIn discussion, Gary Illyes, an Analyst at Google, disclosed that the search engine employs a binary method when evaluating a website’s lastmod signal from sitemaps.

This insight came about as Illyes recommended that website owners transition to the latest WordPress 6.5 update, which now intrinsically supports the lastmod element in sitemaps.

During the discussion, Mark Williams-Cook inquired whether Google employs a “reputation system” to determine the reliability of a site’s reported lastmod dates. In response, Illyes unequivocally stated, “It’s binary: we either trust it or we don’t.”

No Shades Of Gray For Lastmod

The lastmod tag is pivotal as it indicates the date of the most recent substantial update to a webpage. This information helps search engines in prioritizing the crawling and indexing process.

Illyes’ assertion implies that Google does not take into account a website’s historical performance or incrementally build trust in the reported lastmod dates. Google simply either trusts the lastmod timestamps provided in a site’s sitemap or chooses to disregard them.

This binary methodology underscores the necessity of correctly implementing the lastmod tag and ensuring it is updated only when significant changes are made. Accurate lastmod values are crucial for effective crawl prioritization.

Illyes praised the WordPress developer community for their efforts on version 6.5, which now automatically populates the lastmod field without requiring additional configuration.

Accurate Lastmod Essential For Crawl Prioritization

While the native lastmod support in WordPress 6.5 is indeed convenient, its true benefit hinges on Google trusting that it is used correctly. Misrepresenting the lastmod dates could result in Google ignoring this signal when determining crawl schedules.

With Illyes affirming Google’s position, it becomes clear that there is no margin for error in the use of this tag. Precision and accuracy are paramount for the signal to be recognized and utilized by Google.

Why SEJ Cares

Understanding Google’s approach to the lastmod tag is vital for ensuring that updated content is accurately reflected in search results. It is an all-or-nothing scenario—if the dates are deemed unreliable, the signal might be disregarded across the entire site.

Armed with the information provided by Illyes, website owners can ensure their implementation aligns with established best practices, thereby enhancing the likelihood that Google will trust and act on the lastmod dates in their sitemaps.


Featured Image: Danishch/Shutterstock

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