using nofollow links to identify unnatural linking patterns
(also https://www.wordstream.com/blog/ws/2012/07/30/unnatural-links)
Nofollow links are links with rel=”nofollow” added to the HTML tag. This tells search engines to ignore the link, and so they aren’t considered in search engine optimization. For years, the Google search engine has simply ignored links with the nofollow attribute. Last month Google announced that they would begin viewing nofollow links as “hints” to determine if the link should be ranked. This change is officially starting in March 2020.
One reason this change was introduced was to help the pagerank algorithm. “Looking at all the links we encounter can also help us better understand unnatural linking patterns” Google said in its announcement, “By shifting to a hint model, we no longer lose this important information, while still allowing site owners to indicate that some links shouldn’t be given the weight of a first-party endorsement”. The unnatural linking patterns mentioned in the announcement refer to artificial links intended to manipulate a page’s ranking – by using nofollow links as hints instead of simply ignoring them, Google may be able to better identify and react to unnatural linking patterns which disrupt their SEO.