Google’s Gary Illyes: Lastmod Signal Is Binary

In a recent LinkedIn discussion, Gary Illyes, Analyst at Google, revealed that the search engine takes a binary approach when assessing a website’s lastmod signal from sitemaps.

The revelation came as Illyes encouraged website owners to upgrade to WordPress 6.5, which now natively supports the lastmod element in sitemaps.

When Mark Williams-Cook asked if Google has a “reputation system” to gauge how much to trust a site’s reported lastmod dates, Illyes stated, “It’s binary: we either trust it or we don’t.”

No Shades Of Gray For Lastmod

The lastmod tag indicates the date of the most recent significant update to a webpage, helping search engines prioritize crawling and indexing.

Illyes’ response suggests Google doesn’t factor in a website’s history or gradually build trust in the lastmod values being reported.

Google either accepts the lastmod dates provided in a site’s sitemap as accurate, or it disregards them.

This binary approach reinforces the need to implement the lastmod tag correctly and only specify dates when making meaningful changes.

Illyes commends the WordPress developer community for their work on version 6.5, which automatically populates the lastmod field without extra configuration.

Accurate Lastmod Essential For Crawl Prioritization

While convenient for WordPress users, the native lastmod support is only beneficial if Google trusts you’re using it correctly.

Inaccurate lastmod tags could lead to Google ignoring the signal when scheduling crawls.

With Illyes confirming Google’s stance, it shows there’s no room for error when using this tag.

Why SEJ Cares

Understanding how Google acts on lastmod can help ensure Google displays new publish dates in search results when you update your content.

It’s an all-or-nothing situation – if the dates are deemed untrustworthy, the signal could be disregarded sitewide.