Documentation

Overview

Simulyn generates realistic mock REST API endpoints from JSON schemas or simple key-value templates. Each endpoint is accessible at a unique URL in this format:

https://simulyn.dev/api/mock/{namespace}/{your-path}

Endpoints can be called directly from frontend code, Postman, cURL, or any HTTP client — no CORS headers or authentication required.

Quick Start

Template Mode

Template mode maps JSON keys directly to Faker.js generator strings. It's the fastest way to get started.

{
  "id": "string.uuid",
  "name": "person.fullName",
  "email": "internet.email",
  "avatar": "image.avatar",
  "company": "company.name",
  "city": "location.city",
  "joinedAt": "date.past"
}

The above template generates array items like { id: "7f9c...", name: "Jane Doe", ... } for every request.

Popular Generators

JSON Schema Mode

JSON Schema mode uses the full JSON Schema Draft-07 spec to generate data. Useful for nested objects, enum constraints, and typed values.

{
  "type": "object",
  "properties": {
    "id": { "type": "string", "format": "uuid" },
    "email": { "type": "string", "format": "email" },
    "age": { "type": "integer", "minimum": 18, "maximum": 80 },
    "plan": { "type": "string", "enum": ["free", "pro", "enterprise"] },
    "address": {
      "type": "object",
      "properties": {
        "city": { "type": "string" },
        "country": { "type": "string" }
      }
    }
  }
}

Query Parameters

All endpoints support optional query parameters to modify the response dynamically — no endpoint reconfiguration required.

# Get 25 users, with a fixed seed for reproducibility
GET /api/mock/acme/users?count=25&seed=42

# Simulate a slow network (800ms delay)
GET /api/mock/acme/users?delay=800

# Test your 404 error handler
GET /api/mock/acme/users?status=404

Request Validation

Optionally define a JSON Schema that incoming request bodies must conform to. When enabled, Simulyn will return a 400 Bad Request with a validation error message for non-conforming payloads.

// Request body validation schema (POST /api/mock/acme/users)
{
  "type": "object",
  "required": ["email", "password"],
  "properties": {
    "email": { "type": "string", "format": "email" },
    "password": { "type": "string", "minLength": 8 }
  }
}

Enable this in the endpoint editor under the "Request Validation" tab. Toggle "Enforce Schema" to activate.

Interactive Playground

Every endpoint has a "Preview" button in the dashboard that opens the interactive playground. Here you can:

• Set query parameters (count, seed, delay, status code) visually.
• Write and send a custom JSON request body.
• Edit the endpoint schema live and save without leaving.
• Inspect the JSON response in a syntax-highlighted Monaco editor.

FAQ