Random JSON Generator
Free online tool to generate mock JSON data for APIs, testing, and prototyping—create random objects, arrays, and nested structures instantly.
Our random JSON generator is a free, browser-based utility to create realistic mock JSON data for development workflows. Whether mocking API endpoints, seeding databases, or testing UI components, it produces varied objects and arrays with strings, numbers, and nests—saving time on manual data creation without any setup.
Common Use Cases for Mock JSON
- ✓API Response Mocking
Simulate backend data for frontend development in React or Vue apps without a live server.
- ✓Database Seeding
Populate test databases with varied JSON records for SQL/NoSQL prototypes or migration scripts.
- ✓UI Component Testing
Feed random JSON into components to verify rendering, validation, and edge cases dynamically.
- ✓Prototyping Workflows
Quickly generate sample data structures for wireframes or API design discussions in teams.
- ✓Validation Tooling
Test JSON schemas, parsers, or formatters with diverse, realistic inputs to ensure robustness.
- ✓Learning & Tutorials
Create example JSON for teaching JavaScript objects, AJAX calls, or data manipulation techniques.
Why Choose Our JSON Generator?
Random Object Generation
Produces varied JSON objects with strings, numbers, booleans, arrays, and nested structures
Customizable Depth
Control nesting levels (1-5) to balance complexity and usability for different testing needs
Array Support
Generates JSON arrays of objects or primitives, mimicking real API paginated responses
Instant Copy & Export
One-click clipboard or download as .json file for seamless integration into code or tools
Syntax Validation
Ensures generated JSON is always valid and parsable, with pretty-print formatting for readability
Client-Side Randomness
Uses browser Math.random() for unique outputs each time—no server calls or data persistence
How to Use the Random JSON Generator
- Select Type: Choose object, array, or nested structure from the options
- Adjust Settings: Set size (e.g., number of items) and depth for complexity control
- Generate Data: Click generate to create random JSON with mixed data types
- Review Output: View pretty-printed JSON with syntax highlighting for easy inspection
- Copy or Download: Use clipboard for code insertion or export as .json file
Understanding Random JSON Generation
JSON (JavaScript Object Notation) is a lightweight format for data interchange, using key-value pairs in objects and lists in arrays []. This tool randomizes content to simulate real-world data, ensuring variety in strings (e.g., "lorem ipsum"), numbers (42.0), booleans (true), and nests.
Example: A simple object {"id":123,"name":"Random User","active":true} or array [{"score":85},{"score":92}].
- Randomness: Based on Math.random() for non-deterministic outputs each run
- Validity: Always parses as JSON.parse() without errors
- Depth Control: Prevents infinite recursion; useful for safe testing
Advanced Features & Capabilities
Type Mixing
Combines primitives (null, undefined simulation via null) with composites for realistic API-like data.
Size Scaling
From tiny (1 item) to moderate arrays (50+), balancing generation speed and data volume.
Regeneration
Refresh button for new variants without resetting settings, speeding iterative testing.
Frequently Asked Questions
Is the JSON deterministic?
No. Each generation is different due to random seeding; use the copy feature to save specific outputs you need for reproducibility.
How deep are nested objects?
Nesting is capped at configurable depths (default 2-3) to avoid overly complex structures and ensure browser performance and usability.
Can I customize the data types?
The tool focuses on standard random types (strings, numbers, etc.); for advanced schemas, generate base and modify manually or use extensions.
Is the output always valid JSON?
Yes, every generation produces syntactically correct JSON, ready for parsing in JavaScript or other languages without errors.
How large can the generated JSON be?
Scalable from small objects to larger arrays (up to 100 items); deeper nests increase size, but it's optimized for quick rendering.
Does it support dates or IDs?
Includes random strings for IDs and timestamps; for precise formats like ISO dates, post-process the output in your code.
Privacy & Security Considerations
This JSON generator maintains secure, private data creation:
- Local Generation: All randomness and output happen in-browser—no data leaves your device
- No Persistence: Generated JSON isn't stored; ephemeral for sensitive prototyping
- Best Practices: Use mock data only; avoid real info in tests to comply with privacy regs
- Related Tools: Follow up with JSON Formatter for cleaning outputs
Integration & Code Examples
Build your own random JSON in JavaScript using recursive functions for custom schemas:
JavaScript Example:
// Recursive function to generate random JSON
function generateRandomJSON(depth = 2, maxKeys = 5) {
if (depth === 0) {
return Math.random() > 0.5 ?
Math.floor(Math.random() * 100) :
Math.random().toString(36).substring(7); // Number or string
}
const isArray = Math.random() > 0.5;
const obj = isArray ? [] : {};
const length = Math.floor(Math.random() * maxKeys) + 1;
for (let i = 0; i < length; i++) {
const key = 'key' + i;
if (isArray) {
obj.push(generateRandomJSON(depth - 1));
} else {
obj[key] = generateRandomJSON(depth - 1);
}
}
return obj;
}
// Example usage
console.log(JSON.stringify(generateRandomJSON(2), null, 2));