A nofollow tag is a rel value that tells search engine bots not to pass ranking value through a specific link. People can still see and click the link normally; only the ranking signal is withheld. Websites often use it on areas they can't fully control or trust, blog comments, forum posts, guestbooks, to reduce the risk of spam links dragging the site into trouble.
In 2019, Google split the single nofollow attribute into three more specific hints: rel="sponsored" for paid or affiliate links, rel="ugc" for user-generated content like comments, and rel="nofollow" kept for everything else a site simply doesn't want to vouch for. All three are treated as hints rather than hard directives now, meaning Google can still choose to consider a nofollow link as a ranking signal in aggregate, even though it usually won't pass value the way a normal link does. Using the right one, sponsored for a paid partnership rather than a generic nofollow, keeps a site's link disclosures accurate rather than just technically compliant.
