AI JSON Generator & Instant Mock API Publisher
Generate perfect JSON from plain English and publish it as a live, publicly accessible mock API endpoint. Get instant, shareable URLs for frontend testing, prototypes, and demos—no backend setup required.
Generate JSON from plain English and instantly publish it as a live, shareable mock API endpoint. No servers, no setup—just instant APIs for prototyping, testing, and demos.
Initializing JSON Engine...
Preparing local environment
What You Get With Published APIs
Real, Live URLs
Get a permanent endpoint you can fetch from any app or tool
Public & Shareable
Share your API URL with teammates, clients, or in documentation
Instant Access
No backend setup, no servers, no deployment—just instant APIs
From Idea to Live API in 4 Simple Steps
No coding required. No server setup. Just describe your data, edit it, and publish.
Describe Your Data
Write a simple prompt in natural language describing the JSON structure you need.
Generate & Edit
Our AI model generates the JSON code. You can then edit the data to fit your exact needs with live validation.
Publish as Live API
Your JSON is instantly validated. With one click, publish it as a live, publicly accessible mock API endpoint.
Save History (Optional)
Log in to save your generated APIs to your history, so you can edit or share them later.
Why Use Our AI JSON Generator?
Instant Live API Endpoints
Turn any generated or edited JSON into a live, shareable mock API endpoint with a single click. Get a real URL you can use immediately in your apps, share with teammates, or use for frontend development and demos—no backend required.
Save Hours of Development Time
Stop manually typing JSON and configuring mock servers. Generate complex JSON structures and get instant API endpoints in seconds—what used to take hours now takes moments.
Eliminate Syntax Errors
The AI is trained to produce clean, valid JSON. Say goodbye to frustrating debugging sessions caused by a missing comma.
Perfect for Learning & Teaching
New to JSON or APIs? Describe what you want in plain English, see how it's structured correctly, and instantly understand how real APIs work by using your own live endpoint.
History & Management
Log in to automatically save your generated APIs. Easily access your history, view past generations, and manage your collection anytime.
Examples: Prompts and Outputs
Try these prompts in the generator above. Edit the output as needed, then publish as a mock API.
Users Array
Prompt: “An array of 3 users with id (number), name, email and createdAt ISO date.”
[
{ "id": 1, "name": "Alice Nguyen", "email": "alice@example.com", "createdAt": "2024-09-15T10:21:00Z" },
{ "id": 2, "name": "Ben Ortiz", "email": "ben@example.com", "createdAt": "2024-09-16T08:05:12Z" },
{ "id": 3, "name": "Chloe Park", "email": "chloe@example.com", "createdAt": "2024-09-17T14:39:50Z" }
]Product Catalog
Prompt: “A product object with id, title, price, tags[], and a nested category object { id, name }.”
{
"id": "sku_1024",
"title": "Wireless Headphones",
"price": 79.99,
"tags": ["audio", "bluetooth", "wireless"],
"category": { "id": 7, "name": "Electronics" }
}Blog Post with Author
Prompt: “A blog post with title, slug, author { name,email}, tags[], and published boolean.”
{
"title": "Demystifying JSON Schemas",
"slug": "demystifying-json-schemas",
"author": { "name": "Priya Shah", "email": "priya@example.com" },
"tags": ["json", "schemas", "best-practices"],
"published": true
}Order with Line Items
Prompt: “An order with id, userId, total, and items[] of { sku, name, qty, unitPrice }.”
{
"id": "ord_8451",
"userId": 2,
"total": 129.97,
"items": [
{ "sku": "sku_1024", "name": "Wireless Headphones", "qty": 1, "unitPrice": 79.99 },
{ "sku": "sku_2301", "name": "USB-C Cable", "qty": 2, "unitPrice": 24.99 }
]
}Popular Use Cases
🛠️ Frontend Development
Build UI components instantly with mock API endpoints—no waiting for backend teams. Get real URLs to fetch from.
📊 API Demos & Presentations
Share live API endpoints with stakeholders, create interactive demos, and showcase realistic API responses instantly.
🧪 Testing & QA
Generate consistent mock data for automated tests, integration testing, and end-to-end test scenarios.
🎓 Education & Tutorials
Teach JSON, APIs, and data structures with real examples. Students get hands-on experience with actual API endpoints.
🚀 Rapid Prototyping
Quickly mock up data structures for new features, validate ideas with stakeholders, and iterate on designs.
📦 Third-Party Integrations
Create mock endpoints to test integrations with tools like Zapier, Airtable, or any service that consumes JSON APIs.
Prompt Tips for Better JSON
- Be explicit about structure and types: "id:number, name:string, active:boolean".
- Specify counts/ranges: "array of 5 items", "2–3 tags per item".
- Define formats: "ISO date strings", "price as number".
- Use nested requirements: "author "author {name,email}" and comments[]".
- Mention sample values or constraints: "US phone numbers", "email pattern".
- Ask for consistency: "unique ids", "slugs lowercase-with-dashes".
How to Use Your Published API
Once published, your API works exactly like any REST API. Here's how to fetch data from it:
🟡 JavaScript / Fetch
fetch('https://formatjsononline.com/api/json/my-users')
.then(res => res.json())
.then(data => console.log(data))
.catch(err => console.error(err));🔵 Python / Requests
import requests response = requests.get( 'https://formatjsononline.com/api/json/my-users' ) data = response.json() print(data)
⚫ cURL
curl https://formatjsononline.com/api/json/my-users
🔴 React / Axios
axios.get('https://formatjsononline.com/api/json/my-users')
.then(response => {
console.log(response.data);
});💡 Real-World Use Cases:
- • Build frontend components without waiting for backend APIs
- • Create interactive demos and prototypes to share with stakeholders
- • Test API integrations in development environments
- • Generate mock data for automated testing and CI/CD pipelines
- • Teach API concepts with real, working endpoints
Frequently Asked Questions
What happens when I publish my JSON as an API?
When you click 'Publish API', your JSON is saved and you get a permanent, public URL (like formatjsononline.com/api/json/your-endpoint). This URL works exactly like a real API—you can fetch data from it using JavaScript, Python, curl, or any HTTP client. It's perfect for testing, prototyping, and demos.
Is the API endpoint really live and accessible?
Yes! Once published, your API endpoint is immediately accessible from anywhere on the internet. You can use it in your web apps, mobile apps, share it with teammates, or use it in API testing tools like Postman. It returns your JSON data with proper CORS headers, so it works from browsers too.
How long do published API endpoints stay active?
Published endpoints remain active indefinitely. You can use them in long-term projects, demos, and educational materials. The endpoints are stable and won't change unless you create a new one with a different name.
Is the AI JSON generator really free?
Yes, absolutely. Both JSON generation and API publishing are completely free. We use leading AI models to offer powerful generation capabilities at no cost, with a fair daily rate limit to ensure availability for all users.
Can I create complex, nested JSON?
Yes. The AI excels at handling complex requests. You can ask for nested objects, arrays of objects, and mixed data types. The more specific your prompt, the better the result. For example, try asking for "An array of 2 blog posts, each with a title, author object (with name and email), and an array of tags".
Is the generated JSON guaranteed to be valid?
While the AI has a very high accuracy rate, it can occasionally make a mistake. That's why we built this tool to seamlessly integrate with our core validator. After generation, the code is instantly checked for validity, and any errors are highlighted for you to fix immediately.
Can I turn the generated JSON into a live API?
Yes—that's the key feature! After generating or pasting your JSON, enter an endpoint name and click 'Publish API'. You'll instantly get a live URL that returns your JSON. This is perfect for frontend development, testing, prototyping, and demos without setting up a backend.
Can I use my own data instead of AI-generated output?
Absolutely. You can paste any JSON data and publish it as an API endpoint. The tool works great for both AI-generated content and your own custom JSON. Just paste, validate, name your endpoint, and publish.
Can I edit the AI-generated data before publishing?
Yes. The JSON editor includes full editing capabilities, real-time validation, formatting tools, and error detection. You can customize any part of the generated JSON before publishing it as an API. Changes are validated instantly.
Do I need to sign up or create an account?
No! You can generate JSON and publish APIs anonymously without any account. However, we recommend signing in (it's free!) so you can save your history and manage your published APIs later.
Ready to Get Started?
Choose from our suite of JSON tools to start processing your data right away.
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