A referral exclusion, called “unwanted referrals” in Google Analytics 4, is a setting that tells GA4 to ignore certain websites as a traffic source, so a visit that passes through them is not credited to them. Its most common use is stopping a payment provider such as PayPal from taking credit for your sales.
How referral exclusion works
GA4 records where each session came from. When someone arrives by clicking a link on another site, the browser passes on that site’s address and GA4 labels the visit a referral. Normally that is useful. The trouble starts when a customer leaves your site partway through a journey and comes back. Paying through a payment gateway such as PayPal, Klarna or Clearpay, confirming a card payment with the bank, or booking through a system hosted on another domain can all bring the customer back to your confirmation page with that other site recorded as the referrer.
In GA4 you add those domains in Admin, under your web data stream’s tag settings, in the list of unwanted referrals. When a visitor returns from a listed domain, GA4 ignores the referrer, so the session keeps its original source. The purchase stays with the Google ad, email or organic search that actually brought the customer.
Domains you own are a related but different case. If visitors cross from your main site to a separate shop or booking domain that you control, the right fix is cross-domain tracking, which carries the visitor’s identity across, and GA4 then stops treating those domains as referrers. A self-referral, where your own domain appears as a referral source, usually means one of these two settings is missing.
Why it matters
Without exclusions, sales pile up under paypal.com / referral or a bank’s domain in your acquisition reports, and the channels that really drove those customers look weaker than they are. It is a common problem in UK ecommerce, where buy-now-pay-later options are widely offered at checkout and card payments regularly involve an extra authentication step with the customer’s bank.
The distortion flows further. GA4 data reaches Google Ads through imported key events and audiences, and it shapes how budget is shared between channels. A shop that sees “referral” among its top revenue sources may cut a campaign that was doing its job.
Common mistakes
- Waiting until the reports look wrong. Unwanted referrals apply only from the date you add them, and past data stays as it was.
- Excluding a site that sends you genuine visitors, such as a directory or partner that links to you, which hides a real source.
- Using exclusions to paper over missing cross-domain tracking between your own sites.
- Using an exact-match condition when the provider returns visitors from several subdomains, so some still slip through.
- Never retesting after switching payment provider or adding a new way to pay.
How to act on it
Open GA4’s traffic acquisition report, choose session source / medium, and filter for “referral”. Any payment provider, bank, booking engine or domain of your own in that list with purchases or key events against it is a candidate. Add each one to the unwanted referrals list, then place a test order with every payment method, arriving each time through a tagged link such as one made with the UTM link builder. The next day, check in the traffic acquisition report that those test orders sit under the tagged source rather than the payment provider.
Note the date of the change in your reporting so the shift in channel figures is explained later. I check unwanted referrals as part of every tracking review in performance marketing, because payment providers are among the most frequent reasons channel reports credit the wrong source.