Fern vs. OpenAPI Generator
Fern generates production-ready SDKs with built-in OAuth token refresh, pagination, retries, typed errors, and comprehensive documentation. OpenAPI Generator produces basic API wrappers that require implementing these features yourself.
Documentation and onboarding
Fern SDKs include comprehensive documentation covering installation, authentication, types, errors, pagination, and retries. OpenAPI Generator provides minimal documentation.
Client ergonomics
Fern provides a single unified client with namespaced resources. OpenAPI Generator uses separate API classes per resource.
Code examples
Authentication and token lifecycle
Fern includes a built-in OAuth token provider that automatically retrieves and refreshes tokens with a configurable buffer before expiration. OpenAPI Generator requires manual token management.
Pagination
Fern provides async iterators for pagination with for await support. OpenAPI Generator returns raw responses with manual cursor tracking.
Code examples
Error handling
Fern generates typed error classes for specific HTTP status codes. OpenAPI Generator uses a generic ResponseError class.
Code examples
Resilience features
Fern includes automatic retries with exponential backoff, configurable timeouts, and request cancellation. OpenAPI Generator requires custom implementation of these features.
Code examples
Logging and observability
Fern includes configurable logging with automatic redaction of auth headers, tokens, and API keys. OpenAPI Generator has no built-in logging.
Code examples
Raw response access
Fern provides a .withRawResponse() method for accessing HTTP response details. OpenAPI Generator uses separate *Raw() methods.
Code examples
Runtime compatibility and packaging
Fern supports multiple JavaScript runtimes with ESM/CJS dual builds and automatic runtime detection. OpenAPI Generator provides ESM/CJS support.
Testing and quality
Fern SDKs include unit and wire tests with linting enabled. OpenAPI Generator doesn’t include tests.