Alejandro Rioja.
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Common Google Analytics Data Errors: A Guide On How To Fix Them

Alejandro Rioja
Alejandro Rioja
7 min read
TL;DR

GA4 has replaced Universal Analytics — the most common data errors today are self-referrals, missing or duplicate tags, broken cross-domain tracking, consent mode gaps, and unfiltered bot traffic, each with a specific fix inside GA4's admin interface.

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Self-Referral Traffic Inflating Session Counts

In GA4, a self-referral happens when your own domain shows up as a traffic source — usually because the tracking tag fires after a redirect, a cross-domain hand-off isn’t configured, or a payment gateway sends users back without carrying the session context.

Fix: Go to Admin → Data Streams → [your stream] → Configure tag settings → List unwanted referrals. Add your own domain (and any payment processor domains like stripe.com, paypal.com) to that list. GA4 will stop attributing those hits as new referral sessions.

Missing or Duplicate GA4 Tags

The symptom is either no data at all (missing tag) or implausibly low bounce rates and inflated event counts (duplicate tag). In GA4, a duplicate tag typically means the Measurement ID fires twice — once via a hardcoded snippet and once via Google Tag Manager.

Fix for missing tag: Use the Google Tag Assistant Chrome extension to confirm the tag fires on every page. For SPAs (React, Next.js, Astro), verify the tag re-fires on route change — GA4’s default page_view event does not auto-fire on client-side navigation without extra configuration.

Fix for duplicate tag: In Google Tag Manager, check whether there is both a GA4 Configuration tag and a separate GA4 event tag that also includes a Measurement ID. Remove the Measurement ID from individual event tags and let the Configuration tag handle it. If you also have a hardcoded snippet in the <head>, pick one delivery method and remove the other.

Cross-Domain Tracking Broken in GA4

If your funnel spans multiple domains — a blog, a checkout page, a third-party booking tool — GA4 needs explicit cross-domain configuration or each domain hop creates a new session.

Fix: In Admin → Data Streams → Configure tag settings → Configure your domains, add every domain that is part of the same user journey. GA4 will automatically pass a _gl linker parameter across those domains to stitch sessions together. Unlike UA, there is no need to manually install a Linker plugin in GTM — the configuration tag handles it when the domain list is correct.

Check it by navigating the funnel yourself and confirming that the Session ID in the DebugView stays consistent across domains.

Campaign UTM Errors

GA4 reads the same UTM parameters as UA (utm_source, utm_medium, utm_campaign, utm_content, utm_term), plus two new ones: utm_id and utm_source_platform. Errors almost always come from one of three places:

Inconsistent parameter casing

GA4 is case-sensitive. utm_source=Facebook and utm_source=facebook are two different values. Standardize to lowercase across all campaign URLs. Use the GA4 URL builder to generate links consistently.

UTMs stripped by redirects

Some URL shorteners and redirect chains strip query parameters. Test your full redirect chain by pasting the URL into a browser and confirming the UTM parameters survive to the final landing page.

Missing UTMs on paid social

Meta, LinkedIn, and TikTok Ads can auto-tag clicks with their own parameters, but those do not populate GA4’s campaign dimensions unless you also add UTMs manually (or use the platform’s UTM auto-tagging feature where available). GA4 does not have a native integration equivalent to Google Ads’ auto-tagging for non-Google platforms.

If your site operates under GDPR, CCPA, or similar regulations and uses a consent management platform (CMP), you need GA4’s Consent Mode v2 (required by Google as of March 2024 for EEA traffic). Without it, Google can no longer model conversions for consented vs. non-consented users, and your data will show unexplained gaps in European traffic.

Fix: Confirm your CMP supports Consent Mode v2 and that it sets ad_storage, analytics_storage, ad_user_data, and ad_personalization signals before the GA4 tag fires. In GTM this means the CMP’s initialization tag must have higher priority than the GA4 Configuration tag, or use a Consent Initialization trigger.

Verify in DebugView that consent_state is being sent with hits from a cookie-declined session — you should see modeled hits, not silence.

Unfiltered Internal and Bot Traffic

GA4 no longer has Views, so you cannot create a “filtered view” the way you could in UA. Instead, filters are applied at the data stream or property level.

Fix for internal traffic: Go to Admin → Data Streams → Define internal traffic. Add your office IP ranges. Then go to Admin → Data Filters, create an Internal Traffic filter, and set it to Active (not just Testing). Until you activate it, the filter does nothing to production data.

Fix for bot traffic: GA4 automatically excludes known bots based on the IAB/ABC International Spiders and Bots list. You cannot add custom bot rules the way you could in UA, but you can cross-reference suspicious traffic by inspecting the session_engaged dimension — bots typically show 0% engaged sessions. For developer and staging traffic, use the traffic_type parameter set to internal on those environments.

Wrong Property or Measurement ID

This is the GA4 equivalent of the old “wrong property” error. It’s common on multi-brand setups where the same GTM container serves several sites.

Fix: In GTM, use a Lookup Table variable that returns the correct Measurement ID based on {{Page Hostname}}. Each domain maps to its own GA4 property. This prevents cross-contamination and is much safer than maintaining separate GTM containers per domain.

Google Analytics 4 Data Errors — 2026 FAQ

Is Universal Analytics data still accessible?

No. Google shut down the UA standard properties in July 2023 and 360 properties in July 2024. The UI is gone and the data is no longer accessible. Everything should be in GA4 now.

Why does GA4 show much lower session counts than UA did?

GA4 changed the definition of a session. In UA, a new session started at midnight, after 30 minutes of inactivity, or on a new campaign hit. GA4 uses a session-start event with a session ID; the same user on the same device across midnight stays in one session. Lower session counts are expected and do not mean data is missing — compare engagement metrics like engaged_sessions instead of raw sessions.

How do I filter out developer traffic in GA4 without Views?

Set a custom dimension in your dev environment: fire gtag('set', {'traffic_type': 'internal'}) in your dev builds, then use the Internal Traffic filter in GA4 Admin to exclude it. This replaces the filtered View pattern from UA.

Yes — with Consent Mode v2, GA4 uses behavioral modeling to estimate conversions from non-consented users rather than dropping those sessions entirely. You need a certified CMP and the v2 signals configured correctly for modeling to activate. Google’s own documentation (verify current) covers which CMPs are certified.

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