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Analyzing Acquisition Data in GA4: HTTP Referrer vs. UTM Parameters
So I’m diving into Google Analytics 4 (GA4) and I’ve heard that it tracks referral traffic using the http referrer field in the request header. If that field is blank, then GA4 uses UTM parameters to figure out the source/medium. If neither are there, then GA4 just says the source of traffic was Direct. But here’s where I’m getting a bit muddled. If both the http referrer info and UTM parameters are there, which one does GA4 use to make the report in acquisition?
To make it clearer, let’s imagine a scenario. Suppose there’s a website called mywebsite.com. Now let’s say somebody named Joe is scrolling through linkedin.com and sees a post with a link that takes him to https://mywebsite.com/?utm_source=linkedin&utm_medium=testsocialpost. This is Joe’s first visit to the site. So in this case, the http referrer info says linkedin.com and the UTM parameters say the source is linkedin and medium is testsocialpost.
Q1) Let’s look at how GA4 generates a report under Reports -> Lifecycle -> Acquisition when you go with the First User Source/Medium dimension. Look at this screenshot of a sample table for another website.
Will the resultant table look something like the one below?| FirstUser source/medium | New users | | ----------------------- | --------- | | linkedin.com/referral | 1 |Or like this?
| FirstUser source/medium | New users | | ----------------------- | --------- | | linkedin/testsocialpost | 1 |Q2) What happens if two people visit mywebsite.com from two distinct posts on LinkedIn. In this case, one post has UTM parameters and the other doesn’t. Would the resulting report table look like the one below?
| FirstUser source/medium | New users | | ----------------------- | --------- | | linkedin.com/referral | 1 | | linkedin/testsocialpost | 1 |Or would the report look different?
I used this site for some of my understanding: https://cxl.com/blog/utm-parameters/
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2 Replies
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Sure thing! The UTM parameters bag the top priority. So for Q1, your Google Analytics report will display ‘linkedin/testsocialpost’. As for Q2, you’ve got it bang on!
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The http referrer field and UTM parameters both allow Google Analytics 4 (GA4) to track the origin of user traffic. In this case, you’re asking if a visitor came from LinkedIn, followed a link that included both UTM parameters and an http referrer field, which would GA4 apply to the report.
For your first question, GA4 would assign the source/medium tracking according to your UTM parameters because they are manually set by you and tend to be more specific than the http referrer. So in the report table, the source/medium will be listed as “linkedin/testsocialpost.”
For your second question, if two different people visit your website from two different LinkedIn posts, where one post includes UTM parameters and the other doesn’t, both parameters will be represented in the GA4 reports. One will show as “linkedin/testsocialpost” (from the link with the UTM parameters) and the other as “linkedin.com/referral” (from the post without UTM parameters). GA4 is able to differentiate and track both sources in this case. In general, keep in mind that UTM parameters are a more customized and specific method of tracking your source mediums compared to the more automatic http referrer field.
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