Google’s “Search Off the Record” podcast recently highlighted an SEO issue that can make web pages disappear from search results.
In the latest episode, Google Search team member Allan Scott discussed “marauding black holes” formed by grouping similar-looking error pages.
Google’s system can accidentally cluster error pages that look alike, causing regular pages to get included in these groups.
This means Google may not crawl these pages again, which can lead to them being de-indexed, even after fixing the errors.
The podcast explained how this happens, its effects on search traffic, and how website owners can keep their pages from getting lost.
How Google Handles Duplicate Content
To understand content black holes, you must first know how Google handles duplicate content.
Scott explains this happens in two steps:
Clustering: Google groups pages that have the same or very similar content.
Canonicalization: Google then chooses the best URL from each group.
After clustering, Google stops re-crawling these pages. This saves resources and avoids unnecessary indexing of duplicate content.
How Error Pages Create Black Holes
The black hole problem happens when error pages group together because they have similar content, such as generic “Page Not Found” messages. Regular pages with occasional errors or temporary outages can get stuck in these error clusters.
The duplication system prevents the re-crawling of pages within a cluster. This makes it hard for mistakenly grouped pages to escape the “black hole,” even after fixing the initial errors. As a result, these pages can get de-indexed, leading to a loss of organic search traffic.
Scott explained: