Google Analytics : what is the difference between "Referral" default system channel" and "referral" medium?

Question

I'm learning the different features of Google Analytics and I have a question about the default channel groups. Especially, I am wondering what is the difference between the default system channel "Referral" and the medium "Referral"

According to this page, the default system channel "Referral" is defined by "Medium" exactly matches "referral". Unless I'm mistaken, I should get the same results if I use the medium or the system channel.

However, there are differences. Here is an example:

• In Acquistion > Overview, I have the results break by the default channel groups. For "Referral", I get 185 sessions

• When I use the "medium" as primary dimension, I get 205 sessions for "referral"

Could you please help me to understand this difference?

Thanks a lot!

Answer 1

this is happening mainly because of the Social channel grouping which rules are defined and executed before that of the Referral grouping. All visits from sites like facebook.com / referral, twitter.com / referral, t.co / referral, etc. are counted in the Social grouping. That's why you see more referral visits with medium as primary dimension.