Apidog vs Fern

Apidog is an all-in-one API development platform that puts design, debugging, testing, mocking and documentation in one tool, so a team works from a single OpenAPI-based source of truth instead of passing specs between Swagger, Postman and a docs site. It runs in the browser and as desktop apps for macOS, Windows and Linux, and it markets itself directly as a cheaper Postman alternative.

Designers build endpoints and JSON Schemas in a visual editor; developers send requests over HTTP, GraphQL, gRPC, WebSocket, SOAP and SSE with Postman-compatible scripts; QA builds visual test scenarios, scheduled runs and performance tests; schema-driven mocks need no code; and interactive docs publish with custom domains. Sprint branches, Git connection, a CLI for CI/CD and self-hosted runners round it out. The free plan covers up to four users; Basic, Professional and Enterprise are billed per member, and documentation readers are free.

It fits teams that want to replace Postman plus a separate docs and mock tool. Stoplight and Redocly are stronger for pure design governance, ReadMe and Mintlify produce more polished public developer portals, and Postman has the larger ecosystem. Apidog's mock and docs features are less mature for large public API programs.

Recent releases focus on AI: an MCP server that feeds API specs to Cursor and other AI editors, an MCP client and AI agent debugger, AI test case generation and schema compliance checks. Apidog also offers an EU data region and an on-premises edition. Import a Postman collection during the 14-day trial to compare.

Fern is a Y Combinator-backed developer tools company that turns API definitions into SDKs and documentation. Postman acquired Fern in January 2026 and said the Fern product and brand would continue. Teams describe their API with an OpenAPI specification or Fern's own definition format, and Fern generates idiomatic client libraries in languages such as TypeScript, Python, Java, Go, C# and Ruby, plus a hosted documentation site whose API reference stays in sync with the spec.

Generation runs from the command line or in CI, so every API change can produce new SDK versions and publish them to registries such as npm, PyPI and Maven automatically. The docs product supports Markdown guides, interactive API playgrounds, versioning, custom domains and AI search over the content, so the same definition powers both code and documentation. A free plan covers documentation for small teams, while paid pricing is custom and depends on the number of SDK languages, endpoints and documentation needs, which places paid use closer to an infrastructure purchase than a self-serve tool.

Fern suits API-first companies that would otherwise dedicate engineers to maintaining hand-written SDKs in several languages. The output is only as good as the spec, so teams need a clean, well-maintained OpenAPI file, and relying on generated code creates some vendor dependence. Speakeasy and Stainless are the closest SDK-generation alternatives, while Mintlify, ReadMe and Redocly compete on the documentation side.