A pocket guide to Feature Flags

A feature flag separates deploying code from releasing it. You merge the change turned off, then decide from PostHog who gets it: your team first, then 5% of users, then everyone. If errors climb at 5%, you flip the flag off without needing a revert.

This guide follows one flag, new-checkout, through its whole life: checked in code, rolled out a few people at a time, switched off when something breaks, tuned with a payload, tested as an experiment, and removed once it has done its job.

Every page assumes a PostHog SDK is in your app. Install it yourself, or let the wizard install it for you: