Feature flag

A feature flag separates shipping code from switching it on. The code carries both paths, and the flag decides which one runs: for everyone, for a share of people or for a named group. That makes gradual rollouts possible, and a kill switch turns a broken feature off with one switch, without a redeploy.

Flags come in three shapes. An on/off flag switches a feature. A flag with variants picks one of several versions, which is also how a code A/B test decides what each person sees. Remote config hands your code a value, such as the number of trial days.

Flags also pile up. One that has served the same value for weeks is dead code with a switch attached, and is worth removing.

In MIRA FIVE

Feature flags sit under Test and release, on the same data and script as your analytics. A flag is on/off, variants or remote config (text, number, true/false or JSON). It is read in your website, on your servers or both, and assigned by browser or by signed-in person. Code reads flags with the script tag, React, Next.js, Nuxt, Astro, Node.js, Convex, PHP or Laravel.

Rules test properties your code passes in, which are never sent to MIRA FIVE, and segments, which are checked on servers only for now. A share handles gradual rollouts, previews work by URL, and every change is kept in a history. A flag that served one value for 30 days is marked ready to remove, and a project holds up to 200 flags.

On a website that collects without consent, a flag gives everyone the same value. Shares, targeting and experiments need full mode with consent, or a server.

Example

The Acme Shop runs four flags: new-checkout (on/off, 25% of people), free-shipping-banner (on/off, everyone, ready to remove), onboarding-steps (2 variants) and trial-days (remote config, the number 14).