Common Mistakes in GA4 Implementation

GA4 is a powerful tool that is often misunderstood. Whether you love it or hate it, every property requires at least some basic customisation to ensure it delivers the value you need. I’ve spent years working with brands to implement GA4—even back in its infancy when it was called “App + Web.” As both a practitioner and a trainer, I’ve seen all kinds of weird and wonderful ways people use it!

In this post, I’ll break down some of the most common mistakes in GA4 implementation. I firmly believe in “doing the basics well” and ensuring the foundation is set up for success.

The most common Mistakes in GA4 Implementation:

Cross-domain tracking

If your website spans multiple domains, e.g. your main site plus a booking platform, GA4 might treat this experience as separate sessions. The issue with this is that it incorrectly buckets your digital marketing data, risking inaccurate ROI data for each channel. It can also result in the outbound click event (called click) being counted inaccurately.

The process for this is often overcomplicated, with just a few adjustments in GA4 admin settings we can ensure sessions are tracked without being fragmented.

Referral exclusion

Similarly to above, if your users have to navigate via a payment portal such as stripe, worldpay or paypal, you will need to exclude referrals from these domains to ensure they are not classed as an acquisition channel. If you’re seeing a high amount of referral tracking, you likely need to review this setting.

Data Retention

Update your data retention! Do it, do it now!

By default, GA4’s data retention setting is set to just 2 months. If you don’t update this to 14 months, you’ll lose access to event-level data beyond that short window when using Explorations — GA4’s most powerful tool for analysing user behaviour. While aggregated reports remain available, they lack the flexibility and depth of Explorations, meaning you’ll miss out on crucial insights. Since this setting can’t be applied retroactively, updating it should be one of the first things you do when setting up your GA4 property.

Implementing via GTAG instead of GTM

This is a bit subjective, but I don’t believe I have ever suggested to a client to implement their GA4 datastream using the basic GTAG (global site tag) method. While it still works, it’s a far more rigid approach that limits your flexibility to customise event tracking, manage multiple tags, and integrate with third-party marketing tools.

Using Google Tag Manager gives you far more power and autonomy over your analytics implementation, you can configure event tracking without constantly going back to developers to tweak the code and waiting for releases! Plus, when it comes to compliance, GTM makes integrating Consent Mode v2 much simpler, your analytics and marketing complies with Google’s Privacy Policy.

Misunderstanding

Lack of custom event tracking

GA4 automatically tracks a handful of events using enhanced measurement (page views, scrolls, site search). Many businesses assume that simply adding GA4 to their site with enhanced measurement is enough—and then wonder why their reports feel underwhelming or unhelpful. This often leads to a negative perception of GA4 when, in reality, the problem isn’t the tool—it’s the lack of customisation. I’m looking at you, GA4 haters!

The power of GA4 comes with tailoring it to your business needs, tracking important user interactions then marking them as key events. This will provide more relevant and actionable data specific to your business objectives. You reap what you sow! If you have no idea where to start with this, then reach out your friendly analytics specialist.

User, Session & Event Scope

One of the most common areas of confusion that I find when delivering GA4 training is how different dimensions and metrics are scoped – by User, Session and Event. This leads to misinterpretation of data and often frustration when crossing them over and seeing (not set).

User Scoped

Applies to Google’s best knowledge (i.e. cookies) for the entire journey for an individual user, for example their first channel source and demographics.

Session Scoped

Applies to a single visit from the user such as their traffic source, landing page and session duration. Sessions are a count of the session_start event in which some of these dimensions are applied.

Event Scoped

Every interaction such as page views, button clicks and purchases are events. You can add multiple parameters to events for better context.

This is a really important point I try to get across in my training, as this gives you more confidence when navigating the interface and deep-diving the data using explorations.

Engagement/Bounce Rate

A common GA4 misunderstanding is how Bounce Rate has changed. In Universal Analytics (UA), Bounce Rate measured the percentage of single-page sessions with no further interaction—often seen as a negative metric. In GA4, the focus has shifted to Engagement Rate, which tracks the percentage of sessions where a user has:

• Spends 10+ seconds on the site
• Views at least 2 pages/screens
• Triggers a conversion event

GA4 still has Bounce Rate, but it’s now just the inverse of Engagement Rate (e.g., 70% engagement = 30% bounce). I’d always suggest focussing on Engagement Rate, glass half full attitude!

Closer

GA4 is a powerful tool, but only when set up and used correctly. With the right foundations in place, it can unlock valuable insights that drive smarter, data-led decisions.

In another article, we discuss the key features of ga4 that you should know about, read today.

If you’re unsure whether you’re getting the most out of your GA4 setup, my workshops will give you the clarity and confidence to take control of your data. Delivered in focused 2.5-hour sessions, they provide practical, hands-on guidance tailored to your role—so you get the support you need and can get back to business with confidence.

If you need support with GA4 Set-up, please get in touch with our team, or we also provide GA4 training.