Fern

Instantly offer interactive API Docs & SDKs in multiple languages.

Start with OpenAPI, AsyncAPI, gRPC, or OpenRPC.

[Fern @buildwithfern]

Unleash switched from Docusaurus and Kapa to Fern to build docs for humans and agents.

"Fern nails the AI readiness piece better than any other docs platform we've seen." — Melinda Fekete, Documentation Lead at Unleash

Read more: https://t.co/Ah8xBkZMFq

[Kapil Gowru @kapilgowru]

Stoked to share our revamped site for Fern: https://t.co/5LK8VpGk1I. How'd we do? The three principles that guided our process in thread.

[Fern @buildwithfern]

@Amank1412 Use Fern. https://t.co/iXAiUrYGJu

[Fern @buildwithfern]

Introducing Fern Replay 🔁: https://t.co/Vi9FrkOazr

Until now, customizing a Fern-generated SDK was file-level: let the generator overwrite your edits, or .fernignore the file and own it yourself forever. Replay is the line-level answer. After each regeneration, Replay detects your edits and ships the result as a single PR for review.

Works across every SDK language. Generally available and already running in production at @Frame_io , @auth0, and @smallest_AI

Built by Tanmay Singh

[Fern @buildwithfern]

@jerryjliu0 we'd love to help you out. DMs are open or book a demo here: https://t.co/iXAiUrYGJu

[Fern @buildwithfern]

@raunakdoesdev @speakeasydev 🙋 ready to play ball.

we generate enterprise-grade SDKs for @auth0, @Square, and @ElevenLabs.

offering discounted migration services for all stainless customers, give us a shout

https://t.co/iXAiUrYGJu

[Fern @buildwithfern]

@RuhanPonnada @raunakdoesdev @speakeasydev no bros we are very much not cooked. still here with docs and a cli generator too.

https://t.co/wYYNtMFVr8

[Fern @buildwithfern]

@AnthropicAI Claude, @OpenAI Codex, and @cursor_ai already build through the terminal, making the command line the default interface between APIs and agents. But most APIs still don't ship a CLI.

The same API spec that powers Fern Docs and SDKs can now generate a fully functional CLI alongside them.

Fern generates the CLI as a statically linked @rustlang binary that works as:
• A native CLI for agents and developers
• An MCP server for clients like @claudeai and @ChatGPTapp

[Fern @buildwithfern]

Modern development is agent-native. The terminal is the lowest-friction surface for agents to operate in, so we built a CLI generator.

We’re onboarding early access customers now at: https://t.co/SI0m1ISg21

[Fern @buildwithfern]

Try it out on your docs by adding `?shakespeare=true` to any docs site built with Fern, like NVIDIA's: https://t.co/o46i7U3CW7

April Fools idea crafted by @kapilgowru, Devin Logan, and Sarah Bawabe.

Read more: https://t.co/BHugwCNq3M

[Fern @buildwithfern]

Modern docs feel too casual. They lack the gravitas your product deserves.

Today we've shipped Shakespeare mode for Fern Docs. Render thy docs in a noble verse!

See it live: https://t.co/osv7GCZ4C3

Background music generated by @ElevenLabs

[Fern @buildwithfern]

Documentation pages aren't static. As a feature matures, the job a page needs to do changes and the structure underneath needs to change with it.

Fern's technical writer walks through three pages she recently rebuilt and what drove each one: https://t.co/UPptnLmRmj

[Fern @buildwithfern]

Now, docs reviewers don’t need a new preview link for every commit.

Our new GitHub Action comments on your PR with:
• A fixed, named preview link
• Links to every changed page

Learn more: https://t.co/TUHPL8dqGo

[Fern @buildwithfern]

Our only technical writer ships 20,000 new lines of docs a month. Here's how she actually uses AI (@AnthropicAI @cognition @NotionHQ) to do it — and what it still can't do on its own. https://t.co/LVn4iYNKvm

[Fern @buildwithfern]

Great docs should feel effortless. That means the small stuff matters—smooth arrows, no flickering icons, dialogs that ease open.

Frontend engineer Sarah breaks down six small UI improvements she shipped to Fern Docs and why they're worth getting right: https://t.co/YJRZU8vfR8

[Fern @buildwithfern]

Here's what Elijah Skeirik, Technical Writer at Payabli, had to say about it:

“Getting set up with the Rust SDK was genuinely a breath of fresh air. I ran like three commands, and then I could use our API with all of the thoughtful additions that Fern adds into their generated SDKs.”

[Fern @buildwithfern]

𝗜𝗻𝘁𝗿𝗼𝗱𝘂𝗰𝗶𝗻𝗴 𝗙𝗲𝗿𝗻'𝘀 𝗥𝘂𝘀𝘁 𝗦𝗗𝗞 𝗴𝗲𝗻𝗲𝗿𝗮𝘁𝗼𝗿 🦀

Generate a type-safe Rust SDK from your API spec — with async/await, streaming, and idiomatic error handling. Built for performance-critical applications. Includes wire tests to verify correctness and one-command publishing to https://t.co/C7ZSUhKmwr.

Read more: https://t.co/Uh5l1zvhxv

Built by Naman Anand

[Fern @buildwithfern]

Overlays are an official OpenAPI standard that customizes a spec without modifying the original file. Add extensions, rename parameters, or use different configs for SDKs vs Docs — all while keeping your source spec clean.

OpenAPI + Overlays = (𝘣𝘦𝘵𝘵𝘦𝘳) OpenAPI

[Fern @buildwithfern]

𝗡𝗼𝘄 𝘀𝘂𝗽𝗽𝗼𝗿𝘁𝗶𝗻𝗴 @OpenApiSpec 𝗼𝘃𝗲𝗿𝗹𝗮𝘆𝘀

Learn more: https://t.co/qRJJF5ivZS

Built by Thomas Baker