For AI agents: a documentation index is available at the root level at /llms.txt and /llms-full.txt. Append /llms.txt to any URL for a page-level index, or .md for the markdown version of any page.
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HomeAPI DefinitionSDKsDocsCLI & API Reference
HomeAPI DefinitionSDKsDocsCLI & API Reference
  • Introduction
    • Overview
    • Language Support
    • SDK Customer Showcase
  • Capabilities
    • Strongly Typed
    • Idiomatic Method Names
    • Schema Validation
    • Discriminated Unions
    • Multipart Form Data
    • Forward Compatibility
    • Registry Publishing
    • Auto-Pagination
    • OAuth Token Refresh
    • Retries with Backoff
    • Webhook Signature Verification
    • Idempotency Headers
    • Server-Sent Events
    • Integration Tests
    • Code Snippets
    • Augment with Custom Code
    • Merging Multiple APIs
    • WebSockets
  • Reference
    • Configuration
  • Guides
    • Generate your First SDK
    • Preview your SDK Locally
    • Publish a Public-Facing SDK
  • Alternatives
    • Speakeasy
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On this page
  • 1. Fern is an all-in-one: SDKs + Docs
  • 2. Fern SDKs are more widely consumed.
  • 3. Fern offers more Generally Available SDK languages.
  • 4. Speakeasy generates Terraform providers.
  • 5. Fern SDKs come with generated tests.
  • 6. Fern supports OAuth + DPoP.
  • 7. Fern’s file structure is resource based.
  • 8. Speakeasy offers a management dashboard.
  • 9. Fern SDK methods support configuring timeouts, retries, auth, etc.
Alternatives

Speakeasy

How do Fern and Speakeasy differ?
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Speakeasy, similar to Fern, supports generating SDKs for APIs in multiple languages. Below, we walk through the different capabilities of Fern and Speakeasy.

1. Fern is an all-in-one: SDKs + Docs

If you choose Speakeasy, you can integrate with third-party documentation providers or use its native Scalar integration. With Fern, you’ll be able to generate SDKs and Docs with embedded code snippets.

API Docs with SDK code snippets (generated by Fern)

2. Fern SDKs are more widely consumed.

Fern’s SDKs are battle-tested and have been downloaded millions of times.

LanguageFernSpeakeasy
TypeScript120k weekly downloads (Cohere)85k weekly downloads (Mistral AI)
Python6 million lifetime downloads (ElevenLabs)17 million lifetime downloads (Unstructured)

3. Fern offers more Generally Available SDK languages.

LanguageFernSpeakeasy
TypeScript✅✅
Python✅✅
Java✅✅
Go✅✅
C#✅✅
PHP✅✅
Terraform❌✅
Ruby✅❌ (Alpha)
Unity❌❌ (Beta)

4. Speakeasy generates Terraform providers.

Speakeasy supports generating Terraform Providers from your OpenAPI Specification. In order to generate the terraform provider, a user must annotate their OpenAPI with several extensions.

5. Fern SDKs come with generated tests.

Fern handles generating unit tests and integration tests that run against a mock server. Every SDK method is tested and publishing is blocked if any failures are encountered.

Fern SDK Test Workflows

On the other hand, Speakeasy supports contract testing, server mocking, and API sequence testing to streamline development workflows. (example).

6. Fern supports OAuth + DPoP.

FeatureFernSpeakeasy
Bearer✅✅
Basic✅✅
Custom Headers✅✅
OAuth Client Credentials✅✅
OAuth Refresh✅✅
DPop (Proof of possession)✅❌

7. Fern’s file structure is resource based.

Fern’s SDKs are organized so that developers can easily find their way around your API.

Fern
Fern's Resource based file structure
Speakeasy
Speakeasy's flattened file structure

8. Speakeasy offers a management dashboard.

Speakeasy offers a management dashboard where you can visualize each SDK and understand the release process. On the contrary, Fern is primarily GitHub + CLI focused.

9. Fern SDK methods support configuring timeouts, retries, auth, etc.

Fern’s RequestOptions are documented and make it easy for developers to control retries, auth, abort, and timeout behavior.

FeatureFernSpeakeasy
Auth Override✅✅
Timeout Override✅✅
Retry Override✅✅