Flagsmith

Flagsmith is an open-source feature flag, remote configuration and experimentation platform, available as SaaS or self-hosted. This integration makes Flagsmith a cohort destination in Amplitude: every cohort you sync appears in Flagsmith as a segment, ready to target with feature flags or experiments, while Amplitude stays the source of truth for who belongs to it.

Use it to

- Roll a feature out to power users, trial accounts or any behavioural cohort you have built in Amplitude, without rebuilding the targeting logic in Flagsmith.

- Run an experiment on a specific cohort — say, users who completed onboarding but never converted — and measure the lift within exactly that group.

- Run a beta with exactly the users your analytics say should be in it.

- Turn a feature off for a cohort that is hitting problems.

How it works

- Each synced cohort becomes a segment in the Flagsmith environment your sync key belongs to. Change the cohort definition in Amplitude and the segment follows.

- Members are matched to Flagsmith identities by identifier: Amplitude's User ID must be the same value your application uses to identify users in Flagsmith.

- Supports Amplitude's one-time, scheduled (hourly/daily) and real-time syncs. Additions and removals are applied in the background, usually within minutes.

Setup

1. In Flagsmith, go to Segments → Create Segment → Amplitude, choose the environment and create a cohort synchronisation key.

2. In Amplitude, add Flagsmith as a destination, paste the key, and map User ID → Flagsmith Identifier.

3. Open a cohort, click Target users, choose the Flagsmith destination and a cadence, then Sync.

Requirements: a Flagsmith paid plan, and a shared identifier between Amplitude and Flagsmith.

Documentation: https://docs.flagsmith.com/third-party-integrations/cohort-synchronisation/amplitude