A/B test

Showing two versions to randomly split users and measuring which one moves a chosen metric.

Random assignment makes the groups comparable, so the difference in the metric can be credited to the change. Results need enough traffic: with a few hundred visitors a week, only large effects show up, and checking every day until something looks significant produces false winners. Feature flags usually do the splitting.

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Related terms

Feature flags: Switches in code that turn a feature on or off for some or all users without a new deploy.
Conversion funnel: The ordered steps users take towards a goal, such as visit, sign-up and payment, with the share who get from each step to the next.
Activation rate: The share of new users who reach the first real use of a product within a set time.

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