Nofollow
A link attribute (rel="nofollow") that tells search engines not to pass ranking credit through that link. Used for paid links, user-generated content, and untrusted sources.
Why It Matters
Nofollow was created to combat link spam. Before it existed, comment sections, forums, and guestbooks were flooded with links from spammers trying to manipulate rankings. Nofollow let site owners say "this link exists, but I'm not vouching for it."
Since 2019, Google treats nofollow as a "hint" rather than a directive. It may choose to use nofollow links for discovery and ranking purposes. Google also introduced two additional attributes: rel="sponsored" for paid links and rel="ugc" for user-generated content.
In Practice
Use nofollow (or rel="sponsored") on paid links, affiliate links, and any link you've been compensated for. This is a Google requirement - failing to mark paid links can result in penalties for both parties.
Use rel="ugc" on links in comments, forum posts, and other user-generated content where you can't vouch for the quality of every link.
For editorial links to trusted sites in your own content, use standard dofollow links. Nofollowing every outbound link doesn't help your SEO - external links to quality sources can actually strengthen your content's credibility.
Common Mistakes
Treating nofollow as a trust signal, or adding it to every outbound link out of fear. Nofollow tells Google not to pass equity through a link - it doesn't make a site trustworthy, and blanket nofollows can starve your own relevance signals.
Sources & Further Reading
Where to verify this yourself - Google's own documentation, industry reporting, and how we apply it at Underdog. Don't take our word for it; check the source.
Related Terms
Glossary
Link Equity
The ranking value passed through links from one page to another - also called link juice.
Glossary
Backlink
A link from another site to yours - still one of Google's top ranking factors.
Glossary
Link Building
Acquiring backlinks from other sites to build authority - effective when done right.
Glossary
PageRank
Google's original link-based algorithm for measuring page importance - still a factor.
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