One overriding rule applies: enter the domain that the GA4 property selected for the audit actually measures. To understand why, it helps to know exactly what the address is used for.
What we use the address for
An audit consists of two parallel examinations. The first - the GA4 configuration analysis - happens through the API and covers the entire property, regardless of how many domains it measures. The second - the live site scan - applies only to the domain entered in the wizard: our scanner visits it like a regular user and checks the actual implementation (does the tag load, does it duplicate events, how does it behave with consent).
In other words: the URL decides where we verify the implementation in practice - the GA4-side configuration gets examined in full either way.
Typical scenarios
A company site plus a store subdomain in one property (company.com and shop.company.com)
Enter the domain where the key traffic and conversions happen - for e-commerce that's usually shop.company.com. That's where you most need confirmation that the tag and purchase events work. Cross-domain setup, data streams and referral exclusions get verified on the GA4 side regardless of your choice.
Several country domains in one property (company.com and company.de)
Enter the domain of the market you care about most in this audit - that's the one the live scan covers. The GA4-side configuration, shared between both versions, gets examined in full either way. Note that a rescan of the same project always covers the same domain as before - you can't change the address within an existing project.
A separate GA4 property for each domain
The simplest case: each domain + property pair is a separate project. Run an audit for each - just remember they count individually toward the project limit of your plan.
Language versions in subfolders (company.com/de/)
Enter the main domain - subfolders are part of the same website and the same data stream.
A staging / test domain
Audit production. Test domains usually have the GA4 tag disabled or different, indexing blocked or password protection - the live scan won't see the real implementation there, and the property's data comes from production anyway.
Technicalities when typing the address
https:// - we add it automatically.www prefix doesn't matter for the scan - we follow redirects just like a browser.shop.company.com, not shop.company.com/category/shoes).The domain mismatch warning
If in step 3 of the wizard you select a property whose data stream points to a different domain than the entered address, we show a warning along the lines of: "This property's data stream points to company.com - not company.de". You can continue - sometimes it's intentional (e.g. you're auditing a subdomain while the stream is registered on the main domain) - but first make sure you didn't pick the wrong property by accident. This warning catches one of the most common mistakes: auditing the "wrong" property on accounts with many similarly named ones.
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