Noreferrer (rel=“noreferrer”) is a keyword in the “rel” HTML link attribute that instructs the browser not to send any referrer information to the target resource when the user clicks the link on a page. It also instructs the browser to behave as if the “noopener” is specified in the “rel” attribute.
In simple terms, this means that when someone clicks on the link with the “noreferrer,” the server of the target resource won’t know where the visitor came from. And in Google Analytics, this visit will be shown as Direct Traffic, not Referral.
The “noreferrer” has no direct impact on SEO. Such links are crawlable and pass link juice.
You may want to add “noreferrer” to the external links on your website to add another layer of security and privacy for your visitors. However, even when “noreferrer” is not specified, the only referrer information that the modern browsers send is the domain name.