SDK user features | Fern Documentation

Fern-generated SDKs provide a consistent set of features across all languages to help developers interact with your API. Usage information is auto-generated in your SDK’s README, which you can customize.

Installation and basic usage

Users install SDKs using standard package managers (npm for TypeScript, pip for Python, Maven/Gradle for Java, etc.) from language-specific registries.

Users initialize the client with your API’s base URL and any required authentication, then call methods on the client to interact with your API. Generated SDKs support modern runtimes across languages.

Error handling

When the API returns a 4xx or 5xx status code, the SDK throws an error that includes the status code, error message, response body, and raw response object.

Customization options

Your SDK users can configure individual requests using language-specific options:

Option	Description	Availability
Timeouts	Configure request timeouts (default: 30 seconds for C# and PHP, 60 seconds for all other languages)	All languages
Retries	Configure maximum retries (default: 2 with exponential backoff for 408, 429, and 5xx responses)	All languages except Ruby and Swift
Custom HTTP client	Override the default HTTP client for unsupported environments or custom requirements	TypeScript, Python, Java, PHP, and Swift
Custom headers	Send additional headers with any request	TypeScript, Java, and Swift
Raw response data	Access response headers alongside parsed data	TypeScript, Python, and Go
Query parameters	Add extra query string parameters	TypeScript and Swift
Abort signals	Cancel in-flight requests	TypeScript only