Why Do Nelio A/B Testing and Google Analytics 4 Show Different Data?

Nelio A/B Testing and Google Analytics 4 (GA4) collect data for different purposes and may use different tracking methods. As a result, the numbers reported by both tools may not always match exactly.

This is expected and does not necessarily indicate a tracking problem.

Nelio A/B Testing Only Tracks Visitors Participating in a Test

Google Analytics may track all visitors who access a page, whereas Nelio A/B Testing only includes visitors who actually participate in a test.

For example, a visitor may not participate in a test if:

• You have limited the percentage of traffic that participates in the test.
• The visitor does not match the test’s segmentation rules.
• The visitor is otherwise excluded from the test.

As a result, the number of page views reported by GA4 for a page may be higher than the number of tested page views reported by Nelio A/B Testing.

Nelio A/B Testing and GA4 Measure Different Things

The metrics shown by Nelio A/B Testing are designed specifically to evaluate experiments. They include tested page views, conversions, conversion rates, and other data associated with the variants in a test.

GA4, on the other hand, is a general-purpose analytics platform that tracks activity across your website according to its own configuration and measurement rules.

Therefore, similarly named metrics in both tools should not necessarily be expected to produce identical values.

Tracking Configuration Can Also Cause Differences

Differences may also result from how each tracking system is configured or loaded on your website.

For example, consent management tools, cookie settings, traffic exclusions, segmentation rules, caching solutions, or other plugins and scripts may affect whether an event is recorded by Nelio A/B Testing, GA4, or both.

If the difference between the two tools is unexpectedly large, check that both tracking systems are working correctly and review the configuration of your test and your analytics setup.

How Can I Identify Test Variants in GA4?

Nelio A/B Testing may add parameters such as nab to URLs while running tests. Depending on your GA4 configuration, these parameters may appear in the URLs collected by Google Analytics.

For more information about the nab parameter and how to prevent it from splitting pages in your GA4 reports, see How Can I Remove the nab Parameter From Google Analytics 4 Reports?