Referrers
A referrer tells you where a click came from — the source page or platform that sent a visitor to your link. It is essential context, and it is frequently missing.
Definition
A referrer (from the HTTP Referer header — note the single 'r', a standardised typo from the original HTTP specification) is the URL of the page from which a visitor navigated when clicking a link. In link analytics, referrer data identifies the origin of each click — enabling source attribution without requiring additional tagging.
When a visitor on a webpage clicks a link, their browser includes the current page's URL in the Referer header of the outgoing HTTP request. The URL shortener's server reads this header and records it as the referrer for that click. This is how "came from Facebook" or "came from yourblog.com/article" appears in link analytics.
How Referrer Data Is Captured
The process is automatic and requires no action by the link creator:
- Visitor is on a web page that contains a short link
- Visitor clicks the link
- Browser sends HTTP request to the shortener's server, including
Referer: https://source-page.com/pagein the headers - Server reads the Referer header and records it against the click event
- Server issues the redirect to the destination
Known referrer domains are categorised automatically: Facebook.com and its variants → social/Facebook; twitter.com, x.com → social/Twitter; google.com → search/Google; and so on.
When Referrer Data Is Absent
Referrer data is missing in a significant proportion of clicks in most real-world campaigns. Common causes:
| Source | Referrer behaviour | Appears as |
|---|---|---|
| Native email apps | Strips referrer | Direct |
| WhatsApp, iMessage, Telegram | No referrer passed | Direct |
| SMS | No referrer | Direct |
| HTTPS page → HTTP destination | Stripped for security | Direct |
| Privacy browsers / extensions | Suppressed | Direct |
| QR Code scan | No referrer | Direct |
This means that for short links shared via SMS, WhatsApp, email newsletters or QR Codes — among the highest-volume link distribution channels — referrer data will typically be absent, appearing as direct traffic.
Solving Missing Referrer Data with UTM Parameters
UTM parameters appended to the destination URL of a short link carry source attribution independently of the HTTP referrer. Adding ?utm_source=email&utm_medium=newsletter&utm_campaign=spring to the destination means GA4 attributes the resulting session to email/newsletter/spring even if the HTTP referrer is absent. This is the standard solution for email and messaging attribution gaps.
For QR Code campaigns specifically, UTM parameters are the only reliable attribution method — QR Code scans never produce referrer data, and UTM tags on the destination URL are the only way to attribute those clicks in destination-side analytics.
Related Terms
FAQ
What is a referrer in link analytics?
The URL of the page from which a visitor clicked a link, transmitted via the HTTP Referer header. Identifies the source of each click. When absent, the click appears as direct traffic.
Why is referrer data missing or showing as direct?
Email apps, messaging apps (WhatsApp, iMessage), SMS and QR Code scans do not pass referrer headers. UTM parameters on destination URLs solve this — carrying source attribution independently of the HTTP referrer.
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