On March 1, the nofollow attribute began to serve not as a directive, but as a hint. From this point on, the search engine will start crawling and indexing links with this attribute. Previously, Google ignored nofollow links.
Google employees John Mueller and Gary Ilsh responded to several questions on Twitter to help users understand how the search will be performed in the light of the innovations. According to John and Gary, most sites won’t notice any meaningful change.
Some SEO experts believe that Google previously viewed nofollow as a hint rather than a directive. They cite an excerpt from the Search Engine Help on nofollow as a compelling argument for their guess. It states that “usually robots do not follow links marked with these rel attributes.” This is evidence that the search engine did not have to strictly follow the nofollow attribute before.