A/B Test

An online randomized experiment that shows one version of a product (A) to some users and a different version (B) to others, at the same time, then measures which version performs better on a chosen metric. It is just a randomized controlled experiment dressed in product clothing.

A/B tests are how companies decide whether a new button colour, headline, or recommendation algorithm is actually an improvement instead of trusting opinions or guesses. The discipline matters: running the test is easy, but running a trustworthy one — correct randomization, enough traffic, the right metric, no peeking — is where most teams stumble.