Google Analytics captures the data of the referral domains, which directs the prospect to the property website. Once the prospect is on the property website, they might get directed to another third-party website for various purposes. When the prospect returns to the initial site, the third-party website is recorded as the Referral domain. In such cases, the data gets polluted as the third-party website is not the actual Referral domain and should be excluded from being considered for the referral domain reports.

Copy The Referral Domain from Old GA Account.

Log into your old Google Analytics account of your property. [https://analytics.google.com/analytics/web/#/report-home/a177029780w245099172p227968168](https://analytics.google.com/analytics/web/#/report-home/a177029780w245099172p227968168)

Add The Copied Referral Domain in The GA4 Account.

Log into the Google Analytics 4 account of the property.

Click on the "pencil icon" to edit the unwanted referrals.

Add the domain which you copied from your property's old Google Analytics account in the domain box. 

You can add more domains that you wish to exclude as unwanted referrals by clicking on "Add condition."

Once you have added the domains, click on "Save."

You have successfully added the unwanted referrals to be excluded.

Google Analytics

Referrals are the segment of traffic that arrives on your website through another source, like a link on a third-party domain. Analytics automatically recognizes where traffic was immediately before coming on your site and displays the domain names of these sites as the referral-traffic sources in your reports.
To ensure your data includes only referrals in which you're interested, you can create a set of conditions that identify the domains whose traffic you don't want to identify as referrals.

How to Exclude Unwanted Referral Domains from GA4