analytics-dictionary / term / experimentation

Feature flag

A feature flag is a switch in code that turns a feature on or off for some or all users without a new release.

Written by Reflective Data experts · updated Oct 5, 2026

Flags let teams ship code safely, roll out gradually, target specific segments and turn something off instantly if there is a problem. When combined with measurement, a flag becomes an experiment.

Retire flags once the rollout is finished, otherwise they pile up as technical debt.

A/B test LaunchDarkly Server-side testing

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Progressive delivery

Progressive delivery releases a change to a small share of users first and expands gradually while…

fooc.md

Flash of original content (FOOC)

FOOC is when visitors briefly see the original page before a client-side test applies the variant.

kameleoon.md

Kameleoon

Kameleoon is an experimentation and personalisation platform covering both web and feature experimentation.

p-value.md

P-value

A p-value is the probability of seeing a result at least as extreme as yours if…

bayesian-statistics.md

Bayesian statistics

Bayesian statistics expresses results as the probability that a variant is better, updated as data arrives.

one-tailed-vs-two-tailed-test.md

One-tailed vs two-tailed test

A one-tailed test looks for an effect in one direction only; a two-tailed test looks for…

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