Nofollow and Dofollow.

Every link can tell a search engine whether it should count as a recommendation. A standard link with no special attribute — what people call 'dofollow' — passes part of the linking page's authority to its target, and that is precisely what makes classic link building valuable. A link carrying rel='nofollow' signals the opposite: please do not follow this link for ranking purposes. The attribute lives in the HTML, so a reader never notices any difference on the page itself.

The nofollow attribute was originally introduced to devalue comment spam. Today it is used for links you cannot or should not vouch for: user-generated content such as comments and forums, paid placements and advertising. Google has since refined the model and also recognises rel='sponsored' for paid links and rel='ugc' for user-generated content. The more specific attribute is the better choice, because it tells Google what kind of link it is rather than only what to ignore.

One important nuance: since 2020 Google has treated these attributes as hints rather than strict instructions, so it may still take a nofollow link into account in some cases. For your own link building the practical rule is unchanged. A natural profile contains a mixture of both, and paid or sponsored links should be marked correctly as sponsored or nofollow. That is a compliance matter at least as much as an SEO one, and regulators take it seriously.

An example: a company that places a paid guest article on a blog should have the link inside it marked rel='sponsored'. An editorially earned link in a specialist article, by contrast, stays dofollow — and that is the kind that genuinely builds authority. If you are unsure which applies, the honest test is simple: did money, goods or a favour change hands to get the link placed? If yes, mark it. Undisclosed paid links are a common route to a manual action.