Referrer
The HTTP Referrer (or Referer) header identifies the URL of the previous web page that linked to the current page being requested.
Reviewed by Alexander Yarovenko · Updated: 2026-06-21
What is an HTTP Referrer?
The HTTP Referrer (spelled Referer in the actual HTTP header due to a historical typo) is a request header that browsers send to indicate the URL of the page a user came from. When someone clicks a link on Page A that leads to Page B, the browser includes Page A's URL in the Referer header sent to Page B's server.
How Referrer Data Is Used
- Analytics — Google Analytics and GA4 use referrer data to classify traffic sources (organic, referral, direct, social)
- Security — servers can validate that requests come from expected origins
- SEO auditing — identifying which sites send traffic to your domain
- Ad attribution — tracking which campaign or partner page drove a conversion
Referrer Policy
Modern browsers and sites can control how much referrer information is shared using the Referrer-Policy HTTP header or <meta name="referrer"> tag. Common values:
| Policy | What is Shared |
|---|---|
no-referrer | Nothing |
origin | Domain only (e.g. example.com) |
strict-origin-when-cross-origin | Full URL for same-origin; domain only for cross-origin |
SEO Relevance
Referrer blocking (common on HTTPS → HTTP transitions and many social platforms) causes traffic to appear as "direct" in analytics, inflating direct traffic numbers and hiding real referral sources. This is sometimes called "dark traffic". Use UTM parameters on campaigns you control to maintain attribution even when referrer headers are stripped.