What is referral?
In web analytics, referral is traffic that lands on your site after a user clicks a link on another (non-search, non-ad) domain. In most tools, the source is the referring hostname and the medium is “referral”. This classification exists across GA4 as well as privacy-first tools like Plausible, Matomo, and Simple Analytics.
How referral traffic works
When a user clicks a link, the browser sends a Referer header with the previous page’s domain. Analytics tools parse it and decide the channel: if it matches a search engine list → Organic Search; if your link has UTM tags → channel comes from those; otherwise it’s counted as referral. In GA4, you’ll typically see session_source as the domain and session_medium as referral; conversions then flow into your Attribution and Attribution Model reports.
Why it matters
Referrals spotlight partnerships, PR hits, community mentions, and backlinks that actually move the needle. They help you understand which mentions push qualified Sessions, Engaged Sessions, and ultimately Conversions, shaping budget and outreach.
Common pitfalls (and fixes)
- Self-referrals (your own domain shows up as a source). Often caused by cross-domain hops, third-party checkouts, or redirects that drop UTMs. Fix with cross-domain linking, preserving UTMs on redirects, and “unwanted referral” exclusions.
- Dark traffic (no referrer) falls into Direct. Happens with some apps, strict referrer policies, or HTTP↔HTTPS transitions.
- Over-crediting in last-click models: a single viral mention can cannibalize other channels; compare First Touch and Last Touch to balance.
Measurement tips
- Treat partner links as a proper Campaign: tag with UTMs. Note: once UTMs are present, that visit is not “referral” anymore—it’s whatever you set in
utm_medium. - Group top referral sources, then analyze User Flow and content pathing to see what keeps visitors moving.
- For recurring communities, build a lightweight “referral cohort” to monitor retention trends alongside Cohort analysis.
- Keep rules consistent across your stack (GA4, Matomo, etc.) via your Tag Management configuration.