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.

Next.js Integration

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