Noreferrer

Noreferrer is related to analytics and tracking. The referrer value shows the previous page where a user came from. By using the noreferrer attribute on a link, you are preventing other pages from seeing that traffic came from a click on your link.

<a href="https://www.website.com" rel="noreferrer">Link to yoursite.com</a>

Noopener

Noopener is related to security. It closes a browser security issue called reverse tab nabbing which lets an attacker have partial access to the previous page and is typically used when a link is set to open in a new tab with target="_blank".

Note: With the release of Chrome 88, all links with target="_blank" will be treated as noopener.

Example:

<a href="https://www.website.com" target="_blank" rel="noopener">Link to yoursite.com</a>

Nofollow

The nofollow attribute was used in the past to tell search engines to simply ignore a link. Google would not crawl these links and did not pass value through them. Their treatment of nofollow links changed in 2020 and now it’s more complicated. They treat nofollow as a hint, which means they can choose to crawl and pass value through them, or not.

Impact on SEO: it depends on whether they decide the links are valuable or not. There’s no way to determine which links they use and which they do not.

Example:

<a href="https://www.website.com" rel="nofollow">Link to yoursite.com</a>