How Does Nelio A/B Testing Assign and Persist Variants for Each Visitor?

When a visitor first reaches content that’s part of an active test, Nelio A/B Testing randomly assigns them to one of the test’s variants. From that point on, the visitor continues seeing the same variant throughout the test.

To maintain this assignment, the plugin stores a small browser cookie (nabAlternative). Whenever the visitor returns to your site, Nelio reads this cookie and displays the same variant again.

Why Does Nelio Keep Visitors on the Same Variant?

Keeping visitors on the same variant is essential for both user experience and reliable test results.

Consistent user experience

Visitors shouldn’t see different versions of the same page every time they return. Showing the same variant creates a predictable browsing experience.

Accurate test results

Each variant represents a different group of visitors. If visitors switched between variants during a test, it would no longer be possible to measure which version actually influenced their behavior. Persisting assignments ensures each visitor contributes data to only one variant.

Is Traffic Always Split Exactly Evenly?

Not necessarily.

Variant assignment is random, so small differences are normal, especially at the beginning of a test or on low-traffic websites. As more visitors participate, the distribution naturally approaches the configured traffic allocation.