Overview | Fern Documentation

The Fern CLI lets you initialize projects, validate API definitions, preview changes locally, and publish documentation and SDKs. This page covers installation and common commands to get you started.

Installation

Check prerequisites

The Fern CLI requires Node.js version 18 or higher and npm version 8.6.0 or higher (ships with Node.js 18).

$ node -v  # Must be v18.0.0 or higher

If your version is below the minimum, download the latest Node.js LTS which includes a compatible npm version.

Install the Fern CLI

Run the following command to install the Fern CLI globally from npm:

$ npm install -g fern-api
$ fern -v  # Verify the installation

Install locally as a project dependency

If you prefer to manage Fern as a project dependency or are working in an environment with limited internet connectivity, install the CLI locally:

Install as project dependency

$ npm install fern-api

Update configuration

In your fern.config.json, set the version to * to use your locally installed version:

fern.config.json

1 {
2   "organization": "your-org",
3   "version": "*"
4 }

See the fern.config.json reference for more details.

Run via package manager

$ npm fern check
$ npm fern generate

CLI workflows by product

The Fern CLI manages both documentation and SDK workflows. Below is a brief overview of the common commands for each. All commands support global options like --log-level for debugging.

For complete CLI documentation, see the command reference.

Docs workflow

When working with Fern Docs, you’ll use these CLI commands. For complete instructions, see the Docs quickstart.

Command	Description
`fern init --docs`	Create a new docs project
`fern docs dev`	Preview docs locally at `localhost:3000`
`fern generate --docs`	Publish documentation to production

SDK workflow

When working with Fern SDKs, you’ll use these CLI commands. For complete instructions, see the SDKs quickstart.

Command	Description
`fern init`	Create a new SDK project
`fern check`	Validate your API definition
`fern generate --preview`	Preview SDKs locally in `.preview/`
`fern generate`	Publish SDKs to production
`fern generate --group <name>`	Generate a specific SDK group