Quick Start

Get a mock API running in under 2 minutes.

1. Initialize

npm

npx fexapi@latest init

pnpm

pnpm dlx fexapi@latest init

bun

bunx fexapi@latest init

yarn

yarn dlx fexapi@latest init

The wizard asks:

Prompt	Default
Port number	4000
Enable CORS?	Yes

This creates your project files:

fexapi/schema.fexapi
fexapi.config.js

2. Define Your Schema

Open fexapi/schema.fexapi and define your endpoints:

port: 4000

GET /users:
  id:uuid
  name:name
  email:email
  age:number

GET /posts:
  id:uuid
  title:string
  body:string
  published:boolean

Each route declares an HTTP method, path, and a list of fields with their types.

3. Generate

npm

npx fexapi generate

pnpm

pnpm dlx fexapi generate

bun

bunx fexapi generate

yarn

yarn dlx fexapi generate

This reads your schema and outputs fexapi/.cache/generated.api.json.

4. Start the Server

npm

npx fexapi dev --watch

pnpm

pnpm dlx fexapi dev --watch

bun

bunx fexapi dev --watch

yarn

yarn dlx fexapi dev --watch

dev --watch will regenerate and reload when fexapi/schema.fexapi, fexapi.config.js, or custom schema YAML files change.

Your mock API is now running. Try it:

curl http://localhost:4000/users

Response:

{
  "users": [
    {
      "id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
      "name": "John Smith",
      "email": "john.smith@example.com",
      "age": 34
    }
  ]
}

5. Control Record Count

Add a count query parameter to get more records:

curl http://localhost:4000/users?count=20

Returns 20 user records. Maximum is 50.

For routes defined in fexapi.config.js, count query values override the route count (still clamped to 1-50).

What's Next

• Configuration — customize ports, CORS, and delays
• Schema Guide — learn the full schema format
• CLI Reference — all available commands