Recently a client noticed that one of the sites sending them quite a bit of traffic was not showing up in the "Referral Traffic" section of Adobe Analytics.
All the rules in Adobe Analytics appeared to be working as expected so that's wasn't' issue.
What was the cause of referring site not showing up?
On further investigation, we noticed that the referring site was using rel="noopener noreferrer" in the anchor tag (<a tag) that was linking to the client's site.
So instead of using <a href="xyz.com"> the site was using <a href="xyz.com" rel="noopener noreferrer"> to link to our client's site. Which was causing the refering site to now show up in the Referral Traffic reports.
What does rel="noopener noreferrer" mean?
rel is an HTML attribute that specifies the relationship between the current document (page) and the linked document (the site or page that is linked).
rel="noopener noreferrer" has two values in this attributes, "noopener" and "noreferrer"
Noopener directs the browser that the page opening from that link can not have any control over the page where the link was placed. Usually, when you open a link in another tab or window, the page that gets opened (child) can have control over the site that it was opened from (parent). Using this value in the rel attribute, you are directing the browser to now give any control to the child window. This value does not have any impact on your analytics.
Noreferrer directs that the browser should not send HTTP referer information to the opening link. That means when a user clicks on the link then the page/site opened by that link will receive no referrer information and hence the traffic will show up as direct traffic in analytics such as Adobe Analytics, Google Analytics, etc.
Since the site that was sending traffic to our client site has "noreferrer" value in the rel attribute, the referring site was not showing up in "Referral Traffic" reports.
Considering that referral information can be lost in many ways, this just being one example, always use UTM parameters or campaign ids when providing your link to any 3rd parties that will be linking to you.