The sponsored tag, rel="sponsored", is one of three link attributes Google introduced in 2019 (alongside nofollow and ugc) specifically for links tied to money changing hands: paid placements, affiliate links, sponsored content, and advertisements. It tells search engines directly that the link's presence is a paid arrangement rather than an editorial recommendation.
Using it correctly matters for two separate reasons, not just SEO risk. Search engines can penalize undisclosed paid links that pass ranking value as if they were organic, which makes proper tagging a defensive move against that risk. But it's also a legal and regulatory matter in many jurisdictions, disclosure requirements around sponsored content and affiliate relationships exist independently of what any search engine cares about, so the sponsored tag often ends up serving both purposes at once: satisfying Google's guidelines and satisfying broader advertising disclosure rules with the same piece of markup. Treated as a hint rather than a hard rule like nofollow and ugc, Google can still factor a sponsored link into its systems in aggregate, but marking it accurately keeps a site's disclosures honest either way.
