Get a single feature flag by key. By default, this returns the configurations for all environments. You can filter environments with the `env` query parameter. For example, setting `env=production` restricts the returned configurations to just the `production` environment. > #### Recommended use > > This endpoint can return a large amount of information. Specifying one or multiple environments with the `env` parameter can decrease response time and overall payload size. We recommend using this parameter to return only the environments relevant to your query. ### Expanding response LaunchDarkly supports the `expand` query param to include additional fields in the response, with the following fields: - `evaluation` includes evaluation information within returned environments, including which context kinds the flag has been evaluated for in the past 30 days - `migrationSettings` includes migration settings information within the flag and within returned environments. These settings are only included for migration flags, that is, where `purpose` is `migration`. For example, `expand=evaluation` includes the `evaluation` field in the response.