Feature flags are switches in software that let teams turn functions on or off at runtime, roll out changes in stages, or test a change on part of the users first. Platforms in this category add targeting rules, approval flows and A/B-testing infrastructure. LaunchDarkly is a well-known non-European reference point.
Because flag code sits inside your application, the availability of the service determines whether a feature works. What happens when the vendor cannot be reached, and which default value then applies, therefore matters. For targeting rules, many solutions send user attributes to the vendor's infrastructure, sometimes including email addresses, account types or location. Experiments also record behaviour per user. Because the vendor's SDK is woven through your code, switching means changing that code yourself. The Data Act asks cloud services for open interfaces and data export, but not for rewriting your integration.
When choosing a European option, look for local evaluation, where rules run in your own process and attributes never leave your environment, a variant you can self-host, clear fallback values, a vendor-neutral SDK interface, audit logs of changes, and experiment data that lands in your own warehouse.