# Configuration
<a name="bb-configuration"></a>

This section covers Blocks for application settings and secrets.

## AppSetting
<a name="bb-app-setting"></a>

A single configuration value or secret. Read and update values at runtime. Mark a setting as `secret: true` to store it as a SecureString. Values are typed and can be read in your API handlers without environment variable boilerplate.

Locally, AppSetting persists values to the filesystem in the `.bb-data/` directory. On AWS, it provisions an SSM Parameter Store parameter (or SecureString for secrets). Best for API keys, feature flags, and any configuration that might change without a redeploy.

For more information, see [bb-app-setting on GitHub](https://github.com/aws-devtools-labs/aws-blocks/tree/main/packages/bb-app-setting).