- Referral data could be disabled (i.e: Internet Explorer, which is still widely used).
- Internet security applications and ad blocking can block referrer data.
- Firewall and proxy servers can filter out referral data.
- Users can use spoof data to prevent on site tracking.
HTTPS – HTTP Referrals
If a publishers site is HTTPS (secure encrypted connection) and your site is HTTP (Insecure connection) then you may not see any referrals, this is due to the data being sent from a secure site HTTPS to an insecure HTTP site. Below are the instances when you may not see referrals in Google Analytics:
- http to http – Referral data sent
- http to https – Referral data sent
- https to https – Referral data sent
- https to http – No referral data sent