Bump.sh vs Fern

Bump.sh is a hosted API documentation platform built by a small, fully remote French team led by CEO Sébastien Charrier. It takes OpenAPI and AsyncAPI definitions from your repository, turns them into fast reference docs, and diffs every new version so breaking changes are flagged and a changelog is generated automatically. It is docs-as-code for teams that treat the API contract as the source of truth.

Every commit or pull request can deploy or preview docs through the CLI or GitHub Action, and API hubs group many APIs into one portal with a custom domain. Pro adds branch management, an API Explorer, release rollback and the automatic changelog. There is no free plan: Basic costs $50 per month for 10 API docs, Pro $120 per month for 30 docs with a 14-day trial, and Custom adds SSO, embed mode and a 99.99% SLA. Open source projects can request free Pro access.

Bump.sh suits platform teams publishing many internal or public APIs, especially event-driven ones, since AsyncAPI support is first class. It is weaker for long guides and marketing-style portals. ReadMe and Mintlify are stronger for narrative docs, Redocly offers similar OpenAPI tooling with more linting and self-hosting, and Stoplight focuses on design-first editing.

The biggest recent change is its new managed MCP platform: Bump.sh generates and hosts MCP servers from API definitions and Arazzo workflow files, with auth and observability, so AI agents can call your API safely. Note that Basic includes only five MCP tools.

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.