GA4 Source and Medium Are Wrong: How to Diagnose Attribution Problems
When GA4 source and medium are wrong, attribution data is being assigned incorrectly. Source and medium describe where a visitor came from and through what channel. Wrong values usually come from missing UTMs, redirects stripping parameters, self-referrals or campaign tagging problems. Diagnose where the wrong value originates.
Table of Contents
- 01.How GA4 assigns source and medium
- 02.What to check first
- 03.UTMs and referrers
- 04.Redirects and cross-domain navigation
- 05.Self-referrals where relevant
- 06.Session attribution and consent
- 07.How to test it
How GA4 assigns source and medium
GA4 assigns source and medium based on the campaign information it collects, which usually comes from UTM parameters on the landing URL. If UTMs are present, GA4 uses them. If they are missing, GA4 falls back to the referrer, and if there is no usable referrer, the visit may be counted as direct. Wrong source and medium values usually mean the UTMs were lost or the referrer was misinterpreted.
| Symptom | Likely cause | What to check |
|---|---|---|
| Direct traffic too high | Missing UTMs, referrer lost | Campaign links, redirects |
| Wrong source | UTM source mislabeled | UTM values on links |
| Self-referrals | Cross-domain or redirect issue | Referral exclusions, linker |
| Organic shown as referral | Referrer not recognized | Referrer, redirect chain |
| Source medium empty | UTMs stripped before capture | Landing URL after redirects |
What to check first
- Check the landing URL for the campaign and confirm UTMs are present.
- Confirm UTMs survive any redirects to the landing page.
- Check the UTM source and medium values for typos or wrong labels.
- Look for self-referrals in the source report.
- Check whether the referrer is being used instead of UTMs.
UTMs and referrers
UTMs are the primary way to control source and medium. If your campaign links do not include UTMs, GA4 falls back to the referrer, which may be wrong or empty. Confirm your campaign links include utm_source, utm_medium and utm_campaign. The relationship between UTMs being present in a URL and how acquisition data appears in GA4 is covered in the guide on GA4 UTM parameters not showing.
Redirects and cross-domain navigation
Redirects can strip UTM parameters before GA4 captures them. If an ad sends a visitor to a URL with UTMs but a redirect forwards to a clean URL, GA4 sees no UTMs and falls back to the referrer or direct. Cross-domain navigation can also produce self-referrals, where your own domain shows as the source. Test the actual landing URL from the campaign and confirm the UTMs survive any redirect.
Self-referrals where relevant
Self-referrals are a common source and medium problem. When your own domain appears as the source, it usually means session continuity broke across domains or a redirect removed the original referrer. GA4 has configuration to handle unwanted referrals, but you should understand the role of the referral in the journey before excluding it. This is covered in the guide on GA4 showing unwanted referrals.
Session attribution and consent
GA4 distinguishes between user acquisition and session acquisition. A returning visitor may show a different source and medium for their session than for their first acquisition, depending on the attribution scope you view. Consent can also affect attribution, because if consent is not given, the campaign data may not be captured. Understand which attribution scope you are viewing before you call a value wrong. High direct traffic is often a symptom of these gaps, covered in the guide on GA4 showing too much direct traffic.
How to test it
- 1.Click a campaign link and confirm the UTMs are on the landing URL.
- 2.Confirm the UTMs survive any redirects.
- 3.Check the GA4 real time or DebugView acquisition for the visit.
- 4.Compare the source and medium to the UTM values.
- 5.If wrong, check redirects, referrers and the attribution scope.
Frequently Asked Questions
Why is my GA4 source showing as direct?
The UTMs may be missing or stripped by a redirect, leaving GA4 with no referrer to use. Check the campaign link includes UTMs and that they survive any redirect to the landing page.
Why does my own domain show as the source in GA4?
That is a self-referral, usually caused by a cross-domain or redirect issue that breaks session continuity. Understand the role of the referral in the journey before excluding it.
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Related Guides
GA4 UTM Parameters Not Appearing Correctly: What to Check
UTMs in the URL is not the same as UTMs in GA4. The parameters have to be captured and processed into the right acquisition dimension. Confirm the URL, the capture and the dimension scope.
GA4 Showing Too Much Direct Traffic: What May Be Breaking Attribution
Some direct traffic is real, but a large direct number often means lost attribution. Check missing UTMs, redirects, referrer loss and untagged links before assuming the direct number is accurate.
GA4 Showing Unwanted Referrals: How to Diagnose Referral Attribution Problems
Do not exclude a referral until you understand its role in the customer journey. Exclude only the ones that distort attribution, like payment processors in your own flow.