CLI reference

Overview

Manage and configure your Fern projects, all from the command line.
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Install Fern CLI

Run the following command to download and install Fern CLI from the npm registry.

$npm install -g fern-api # install Fern CLI
>fern -v # ensure Fern was successfully installed

If you’re experiencing network delays with the global installation, working in an environment with limited internet connectivity, or prefer to manage Fern as a project dependency, you can install the CLI locally:

1

Install as project dependency

Add fern-api to your project dependencies:

$npm install fern-api
2

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.

3

Run via package manager

Use your package manager to run Fern commands:

$npm fern check        # Validate API definition
>npm fern --version    # Check CLI version
>npm fern generate     # Generate outputs

CLI quickstart

Get started with these commonly used commands:

Common Commands
$# Docs Development
>fern init --docs                  # Create a new documentation project
>fern docs dev                     # Preview docs locally at localhost:3000
>fern generate --docs --preview    # Preview documentation changes
>fern generate --docs              # Generate and publish documentation
>
># SDK Development
>fern init                        # Start new SDK project
>fern check                       # Validate API definition
>fern generate --preview          # Preview SDKs in .preview/ folder
>fern generate                    # Generate default SDK group
>fern generate --group ts-sdk     # Generate specific SDK group

The “default SDK group” refers to the group marked as default in your generators.yml. Learn more about default groups.

Common workflows

  1. Initialize a new docs project:
$fern init --docs
  1. Preview locally while making changes:
$fern docs dev
  1. When ready to preview or publish:
$fern generate --docs --preview  # Generate a shareable preview link
>fern generate --docs            # Publish to production
  1. Initialize a new SDK project:
$fern init

  1. Configure your generators in configuration options

  2. Generate SDKs:

$fern generate --preview                     # Preview changes locally
>fern generate --group python-sdk --preview  # Preview specific SDK group
>fern generate                               # Publish to production

During development, use --preview to test your changes locally before publishing. The preview SDK will be generated into the .preview/ folder.