emulate

Getting Started

Local drop-in replacement for Vercel, GitHub, Google, Slack, Apple, Microsoft, Okta, AWS, Resend, Stripe, MongoDB Atlas, Clerk, and Linear APIs. Built for CI and no-network sandboxes. Fully stateful, production-fidelity API emulation. Not mocks.

Quick Start

npx emulate

All services start with sensible defaults. No config file needed:

  • Vercel on http://localhost:4000
  • GitHub on http://localhost:4001
  • Google on http://localhost:4002
  • Slack on http://localhost:4003
  • Apple on http://localhost:4004
  • Microsoft on http://localhost:4005
  • Okta on http://localhost:4006
  • AWS on http://localhost:4007
  • Resend on http://localhost:4008
  • Stripe on http://localhost:4009
  • MongoDB Atlas on http://localhost:4010
  • Clerk on http://localhost:4011
  • Linear on http://localhost:4012

CLI

# Start all services (zero-config)
npx emulate

# Start specific services
npx emulate --service vercel,github

# Custom port
npx emulate --port 3000

# Use a seed config file
npx emulate --seed config.yaml

# Generate a starter config
npx emulate init

# Generate config for a specific service
npx emulate init --service github

# List available services
npx emulate list

Options

FlagDefaultDescription
-p, --port4000Base port (auto-increments per service)
-s, --serviceallComma-separated services to enable
--seedauto-detectPath to seed config (YAML or JSON)

The port can also be set via EMULATE_PORT or PORT environment variables.

Programmatic API

You can also use emulate as a library in your tests. See the Programmatic API page for createEmulator, Vitest/Jest setup, and instance methods.

Framework Integration

Embed emulators directly in your Next.js or Nuxt app so they run on the same origin. See the Next.js Integration and Nuxt Integration pages for setup instructions.