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Why Your A/B Testing Tool (Convert) Shows Higher Visitor Counts Than GA4 and Amplitude

Understand why Convert often counts more unique visitors than GA4 and Amplitude

Author: George F. Crew

IN THIS ARTICLE YOU WILL:

Overview

It is common to observe a measurable difference in visitor counts when comparing data from A/B testing platforms, such as Convert, against standard web analytics tools like Google Analytics 4 (GA4) and Amplitude. In most cases, the A/B testing tool (Convert) will report a higher number of unique visitors than the analytics platforms.
While this may seem like a data integrity issue, the difference is primarily rooted in the fundamental technical strategy each script employs regarding its loading time.

The Technical Explanation: Script Loading Strategy

The core reason for the visitor count difference lies in the order and speed at which each tracking script executes on your webpage, especially in relation to the visitor's overall stay duration.

  1. Convert's Early Execution (High Velocity)
    Convert's script is highly optimized for early and fast loading—often executing and tracking the visitor within the first 600 milliseconds (0.6 seconds) of the page loading.
    This quick execution is intentional, as A/B testing platforms need to initialize the experiment variation before the visitor perceives the page. This strategy ensures Convert captures nearly every click and visit, including those from users who decide to "bounce" almost immediately.
  2. Analytics Platforms' Later Execution (Performance Prioritization)
    Web analytics platforms like GA4 and Amplitude are often implemented to load slightly later in the page lifecycle to prevent them from negatively impacting overall page load performance (Lighthouse/Core Web Vitals scores).
Platform Typical Load Time (Example)
GA4 ~2.5 seconds
Amplitude ~2.0 seconds

If a visitor leaves the page before the respective analytics script has successfully initialized and fired its first event (the page view event), that visit is never recorded.

The Result: Missing the Quick Bounce

The resulting discrepancy is essentially the population of "Quick Bounces"—visitors who arrive and leave the page in less than 2-3 seconds.
Convert captures these quick bounces due to its fast loading.
GA4/Amplitude misses these quick bounces because the visitor has departed before the script finishes loading.
This effect is particularly noticeable on pages with high bounce rates, or for traffic arriving via slower connections (like mobile devices or users in regions with higher network latency).

Workaround and Performance Tradeoffs

Unfortunately, there is no configuration setting within GA4 or Amplitude to simply "turn on" faster tracking comparable to Convert's default behavior.
The only technical way to force GA4 or Amplitude to capture visitors as early as Convert is to implement their scripts synchronously high up in the <head> tag of your website's HTML.

🚨 Caution — Synchronous Loading
While synchronous loading will increase your visitor count accuracy by reducing missed quick bounces, it comes with a major tradeoff: page load performance.
Forcing an analytics script to load synchronously blocks the rendering of subsequent page elements until the script is fully executed.
This can noticeably increase your page's Time to Interactive (TTI) and negatively impact your Core Web Vitals scores.

Conclusion

The difference in visitor counts between your A/B testing platform (Convert) and your analytics tools (GA4/Amplitude) is a result of conflicting technical priorities:
Convert prioritizes Experiment Integrity and loads immediately, capturing all visitors.
GA4/Amplitude prioritize Page Performance and load slightly later, missing very short visits.
Therefore, Convert's count should generally be considered the more comprehensive total of all page arrivals, while the analytics platforms provide a count of engaged visits lasting long enough for their scripts to execute.