Should I Nofollow All External Links on my Website for SEO Purposes?

[Quick]

Hey all should I go back and nofollow the external links on my posts?

For example links where I include the source for images/graphics or links to scientific studies that support my content.

Should I treat affiliate links differently?

I'm mostly worried if Google would interpret this as trying to manipulate the page rank after they've been do follow all this time or if it doesn't really matter.

 

[Ryuzaki]

@Quick, no. If you're referencing someone else's content because it's relevant or used within your own, it should be a dofollow link. If you nofollow them you'll still lose the page rank juice. It affects the receiver of the link and stops them from getting the juice, but it doesn't stop the linker from losing it. The juice flows out and disappears, basically.

You also want to maintain the contextual relevancy by linking to related content. Part of how Google understands what your page is about beyond the content itself is through the content you endorse through linking.

Yes, you should nofollow all affiliate links because they're incentivized and you earn money through them, essentially making them paid links. You aren't endorsing them for editorial reasons, but monetary reasons.