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The GA4 adapter (turn it on under Settings → Analytics) makes ABTestly push one event per exposure into window.dataLayer. Your GA4 property picks it up like any other custom event.

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The event

Per (visitor, experiment, pageview):
The event name is experience_impression. The single most useful field is exp_variant_string, which follows GA4’s convention for experiment slicing.

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In GA4

To slice any GA4 conversion by variant:
  1. Admin → Custom definitions → Create custom dimension.
  2. Dimension name, “ABTestly variant”.
  3. Scope, User (persists across events for this user).
  4. User property, exp_variant_string.
Then in Explorations, add “ABTestly variant” as a dimension. Every built-in conversion report can now be split by variant, alongside your other GA4 dimensions.

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Where the event fires

On exposure. That is once per (visitor, experiment, pageview), not once per goal, not once per session. The event lands at the moment the variant applies, which is what you want for attributing downstream conversions. The GA4 adapter respects the same consent gate as ABTestly’s own beacons. In deferred consent mode, the adapter waits for grant before pushing anything. If you have GA4 consent mode set up on your side, the two systems compose. ABTestly does not push its event until its own consent gate is satisfied; GA4 does not fire its conversion until its own consent mode allows it.

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In preview

Adapter pushes are suppressed in preview. Your GA4 property does not see previewed exposures.

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When the SDK is not on the page

If window.dataLayer does not exist when the exposure fires, the adapter no-ops silently and reports a first-occurrence-per-session /err event. Your dashboard’s Snippet health panel will surface that. Fix: load gtag.js (or GTM’s snippet) somewhere in <head>, before or after ABTestly, either order works, as long as window.dataLayer is defined by the time an experiment first exposes.

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Other analytics adapters

Same shape, different SDK calls, see Product analytics for Segment, RudderStack, Amplitude, Mixpanel.