FeatureFlags.app is a privacy focused, cloud agnostic feature flag management tool designed primarily for .NET Core applications. Its core function is to allow development teams to toggle features on or off, create complex rules, and modify application behavior without redeploying code. The system replaces manual editing of JSON configuration files with a web based interface, enabling instant, code free control over feature flags from any location. The platform emphasizes data privacy by not tracking users, recording session replays, or collecting unnecessary data. It integrates with Microsoft’s feature management libraries, making it a natural fit for teams already using .NET feature flags. The tool supports caching to reduce network calls and allows configuration of cache expiration to balance performance and responsiveness. It does not require Azure or any specific cloud provider; users can deploy it on premises, in any cloud, or on their own infrastructure. Typical use cases include development teams seeking a straightforward, no frills feature flag system, .NET shops wanting native integration with their existing stack, and privacy conscious organizations that prefer not to have their data shared or tracked. The workflow involves creating feature flags and API keys through the web UI, integrating the client library into .NET applications, and then toggling features or setting rules via the interface. A Quick Start Guide is available to help users integrate the tool into their .NET application within minutes.