Google has adjusted its search algorithm to knock so-called "content farms" further down its results.
Such sites are SEO-friendly to attract the search engine's spiders, but don't contain any original, high-quality content.
The algorithm change will affect more than one in ten search queries, said Google Fellow Amit Singhal and principal engineer Matt Cutts in a post on the Google blog.
"This update is designed to reduce rankings for low-quality sites—sites which are low-value add for users, copy content from other websites or sites that are just not very useful," the pair said. "At the same time, it will provide better rankings for high-quality sites — sites with original content and information such as research, in-depth reports, thoughtful analysis and so on."
"Google depends on the high-quality content created by wonderful websites around the world, and we do have a responsibility to encourage a healthy web ecosystem," they added. "Therefore, it is important for high-quality sites to be rewarded, and that’s exactly what this change does."
The change comes at a critical time for Google's search. On one hand, the search giant is under investigation from regulators for how it ranks vertical search rivals.
On the other hand, web users are increasingly relying on social networks to find content, motivating Google to improve the quality of its search.
The algorithm change will roll out in the US first, before hitting other markets.
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