GrowthBook

GrowthBook is an open source platform giving companies the power of customized feature flagging and A/B testing. Feature flag management uses configuration switches to control feature visibility without deploying new code, enabling gradual rollouts, A/B testing, and instant rollbacks. GrowthBook supports four feature types: boolean, number, string, and JSON. Any feature flag can become an A/B test with one click, with GrowthBook automatically assigning users to variants and tracking defined metrics. The platform offers 24 SDKs including React, Python, Android, and iOS. The JavaScript SDK is 9KB, less than half the size of closest competitors. Open source means no vendor lock-in, full transparency in flag evaluation, and self-hosting options for complete data control. Available from Cloud or self-hosted.