All 185 Dependencies

Every package Fern depends on, ranked by repo health score.

Fern is an open-source developer-experience platform for API providers. Point it at an OpenAPI spec (or its own more expressive Fern Definition YAML, plus AsyncAPI and Protobuf support), and its CLI compiles that definition into a versioned Intermediate Representation that every downstream generator consumes. From that single IR, Fern produces idiomatic, type-safe client SDKs for TypeScript, Python, Java, Go, Ruby, PHP, C#, Rust, and Swift, plus server boilerplate and an OpenAPI spec exporter for teams that started from Fern's own definition format.

Beyond code generation, Fern builds and hosts a full documentation website from the same API definition: an interactive API reference, versioned markdown pages, dark mode, and an AI-powered search assistant trained on a team's docs, APIs, and SDKs. Docs built with Fern are used in production by companies like ElevenLabs, LaunchDarkly, and Hume — the CLI can scaffold and preview these sites locally before publishing.

The project originated from Y Combinator's 2023 batch and is maintained by Birch Solutions under the Fern name. It's structured as a large TypeScript monorepo (pnpm + Turborepo) containing the CLI, the IR compiler, the OpenAPI/AsyncAPI/Protobuf importers, every per-language generator, and a `seed/` directory of golden-file SDK fixtures used to regression-test all nine generators on every change. Language generators also ship as Docker images (the `fernapi/fern-*-sdk` family) so they can run locally or in Fern's remote generation service.

Fern's differentiator versus generating SDKs directly from OpenAPI templates is that IR-first design: adding a new spec format doesn't require touching nine generators, and the IR can evolve (via a dedicated `ir-migrations` package) without breaking SDKs already generated by older CLI versions. The CLI itself, all generators, and the OpenAPI/Protobuf importers are Apache-2.0 licensed and free to self-run; the hosted docs dashboard and AI search are Fern's commercial SaaS offering.

14 reqwest-sse 0.1 outdated 26 esbuild-plugin-polyfill-node catalog: 26 mdast-util-gfm catalog: 26 mdast-util-math catalog: 26 mdast-util-mdx catalog: 26 micromark-extension-mdxjs catalog: 27 micromark-extension-math catalog: 28 micromark-extension-gfm catalog: 29 urlencoding 2.1 31 fast-levenshtein catalog: 31 mdast-util-mdx-jsx ^3.1.3 33 httpdate 1 35 object-hash catalog: 35 tmp-promise catalog: 36 multipart-stream-builder ^1.0 37 is-ci catalog: 38 gray-matter catalog: 39 find-up catalog: 39 jmespath.rs 0.3 outdated 39 json-schema catalog: 39 ordered-set ^4.1.0 39 unicode-normalization 0.1.25 40 dedent catalog: 40 remark-gfm catalog: 41 PSR-18: HTTP Client ^1.0 41 http-factory ^1.0 41 strip-ansi catalog: 41 unist-util-visit catalog: 42 ajv-formats catalog: 43 HTTPlug Discovery ^1.0 43 PSR-7 HTTP Message Interfaces ^1.1 || ^2.0 44 pluralize 8.0.0 44 remark-math catalog: 44 remark-math catalog: 45 uuid v1.6.0 45 mdast-util-from-markdown catalog: 46 httpx-aiohttp 0.1.8 outdated 46 openapi-types ^12.1.3 47 cross-env catalog: 47 tinycolor2 catalog: 48 node-xml2js catalog: 49 unified catalog: 50 serde_json_path 0.7 50 serde_yaml 0.9.34 51 cors catalog: 51 jsonwebtoken catalog: 51 mime-types catalog: 51 next-mdx-remote catalog: 52 hmac 0.12 outdated 52 readable-stream ^4.7.0 53 python-dateutil ^2.9.0 55 HTTPX ^0.27.0 outdated 55 rehype catalog: 56 fs-extra catalog: 56 minimatch catalog: 56 tokio-tungstenite 0.24 outdated 58 url-join catalog: 59 glob catalog: 59 node-fetch catalog: 59 ora catalog: 59 serde_qs 1.1.1 59 tracing 0.1 59 tracing 0.2 outdated 59 tracing 0.3 outdated 59 ts-morph catalog: 60 tsup catalog: 61 diff catalog: 62 chardet catalog: 62 Commander.js ^14.0.3 outdated 62 dotenvy 0.15 63 path-to-regexp catalog: 63 webbrowser 1 64 form-data ^4.0.6 64 simple-git catalog: 65 Chalk catalog: 66 Ajv ^8.18.0 66 secrecy 0.10 67 url 1 outdated 67 url 2.3.2 67 remark catalog: 67 tar catalog: 68 base64 0.22 outdated 68 file-type catalog: 68 Lodash catalog: 68 open catalog: 69 semver ^7.6.2 69 serial_test 3.4.0 outdated 70 bytes 1 70 uuid catalog: 71 MDX catalog: 71 sha2 0.10 outdated 72 JSONPath catalog: 73 MSW (Mock Service Worker) 2.11.2 outdated 73 ordered-float 4.5 outdated 73 pin-project 1.1 75 anyhow 1 75 dotenv ^16.0.0 outdated 75 testify v1.9.0 outdated 75 octokit.js ^4.1.4 outdated 75 qs catalog: 75 tempfile 3 76 execa ^5.1.1 outdated 76 serde_json 1 76 thiserror 2 77 Chrono 0.4 77 node-jwks-rsa catalog: 77 num-bigint 0.4 77 serde 1 77 serde 1.0 78 Day.js catalog: 78 ua-parser-js catalog: 79 keyring-rs 3 outdated 79 yargs ^17.4.1 outdated 81 js-yaml catalog: 82 rand 0.8 82 yaml catalog: 83 Octokit REST catalog: 83 mypy ==1.13.0 outdated 83 pytest-xdist ^3.6.1 83 Requests ^2.33.0 83 reqwest 0.12 outdated 84 uuid 1.0 85 esbuild catalog: 85 ws catalog: 86 Express catalog: 88 es-toolkit catalog: 88 isort ^6.0.1 outdated 88 Moment.js catalog: 88 tsx catalog: 88 typing_extensions >= 4.0.0 89 cspell catalog: 89 Immer ^10.1.1 outdated 89 websockets >=12.0 90 Black ^26.3.1 90 boto3 1.35.76 90 Clap 4 90 Clap 4 90 Clap 0.2 outdated 90 Inquirer.js ^9.2.23 outdated 90 Oxlint 1.72.0 outdated 90 prettier catalog: 90 Ruff ==0.11.5 outdated 90 Stylelint ^14.11.0 outdated 90 Typer ^0.6.1 outdated 90 Zod catalog: 91 Protobuf-ES catalog: 91 Playwright ^1.52.0 91 FastAPI >=0.124.0 91 pytest-asyncio ^1.0.0 92 Vitest catalog: 92 futures 0.3 92 futures 0.3 92 LangChain ^1.2.15 92 LangChain DeepSeek ^1.1.14 outdated 92 PHPUnit ^12.5.22 outdated 92 Pydantic ^2.8.2 92 Pydantic ^2.18.2 outdated 92 setuptools ^80.9.0 outdated 92 urllib3 >=2.6.3,<3.0.0 92 Vitest catalog: 93 sentry-cli catalog: 93 posthog-js ^5.35.1 outdated 93 Tokio 1 93 Tokio 0.7 outdated 93 undici catalog: 94 @babel/core catalog: 94 @babel/core catalog: 94 @babel/core catalog: 94 jest ^29.7.0 outdated 94 Sentry JavaScript (@sentry/browser) ^10.48.0 94 ESLint catalog: 94 jest ^29.7.0 outdated 94 jest ^29.7.0 outdated 94 libc 0.2 outdated 95 aiohttp >=3.14.1,<4 95 Axios catalog: 95 PHP CS Fixer 3.5.0 outdated 95 GraphQL.js catalog: 95 Guzzle ^7.4 outdated 95 OpenAI Python SDK ^2.26.0 outdated 95 Puppeteer catalog: 96 NumPy ^2.0 96 pytest ^9.0.3 96 TypeScript catalog: 97 webpack ^5.105.4

All 185 Dependencies

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