What is Feature Flag?
A feature flag (or feature toggle) is a mechanism that lets teams enable or disable functionality at runtime without shipping new code. The feature is built behind a conditional "flag" that can be flipped on or off — for everyone, or for specific segments.
Flags decouple deployment from release. Code can be merged and deployed "dark," then turned on gradually: a percentage rollout, a beta group, or a single customer. If something breaks, the flag is flipped off instantly — a kill switch that's far safer than an emergency rollback.
PMs use feature flags to run A/B tests, do staged rollouts, run betas, and ship risky changes safely. They enable a more experimental, lower-risk release culture. The tradeoff is that accumulated, stale flags add complexity, so teams need hygiene to retire them once a feature is fully launched.
Examples
- A new checkout flow is rolled out to 5% of users via a flag, then ramped to 100% over a week.
- A PM uses a flag to give a key enterprise customer early access to a beta feature.
Where PMs use this
Related terms
A/B Testing
A controlled experiment comparing two versions to see which performs better on a chosen metric.
Minimum Viable Product (MVP)
The simplest version of a product that delivers enough value to learn from real users.
API (Application Programming Interface)
A defined interface that lets software systems communicate and exchange data with each other.