To understand how a link affects your SEO efforts we first need to look at the coding that creates a link.
<a href="https://anothersite.com/anotherpage" target="_blank" rel="noopener noreferrer nofollow">some text</a>
When adding a link to goto an external site, you don’t want your visitors to navigate away from your site so target=”_blank” is added to have the link open in a new browser tab.
The addition of noopener is required for security reasons. The other parameters noreferrer and nofollow are related to SEO and affect PageRank.
Adding noreferer prevents analytics from determining how a visitor arrived to a page. For example, if your website contained a link to NASA using
<a target="_blank" rel="noreferrer" href="https://www.nasa.gov/">NASA</a>
NASA’s internet marketing team would count this page view as direct traffic instead of referral traffic. Direct traffic occurs when someone knows the exact url of a page and types it into their browser to go directly to the page.
The use of nofollow means PageRank will not be directly affected for either website and voids the efforts of SEO’s engaged in link building. However the person visiting the website is not looking at the code and if the content is compelling enough will click on the link. Using nofollow is a double-edged sword because linking to a page which a search engine deems as high quality increases the PageRank of the page containing the link. The opposite is also true, a poor quality page lowers the PageRank of the page containing the link.